Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3193 insertions, 0 deletions

diff --git a/media/ffvpx/libavcodec/avcodec.h b/media/ffvpx/libavcodec/avcodec.h
new file mode 100644
index 0000000000..9a0fe97cad
--- /dev/null
+++ b/media/ffvpx/libavcodec/avcodec.h
@@ -0,0 +1,3193 @@
+/*
+ * copyright (c) 2001 Fabrice Bellard
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_AVCODEC_H
+#define AVCODEC_AVCODEC_H
+
+/**
+ * @file
+ * @ingroup libavc
+ * Libavcodec external API header
+ */
+
+#include "libavutil/samplefmt.h"
+#include "libavutil/attributes.h"
+#include "libavutil/avutil.h"
+#include "libavutil/buffer.h"
+#include "libavutil/dict.h"
+#include "libavutil/frame.h"
+#include "libavutil/log.h"
+#include "libavutil/pixfmt.h"
+#include "libavutil/rational.h"
+
+#include "codec.h"
+#include "codec_desc.h"
+#include "codec_par.h"
+#include "codec_id.h"
+#include "defs.h"
+#include "packet.h"
+#include "version_major.h"
+#ifndef HAVE_AV_CONFIG_H
+/* When included as part of the ffmpeg build, only include the major version
+ * to avoid unnecessary rebuilds. When included externally, keep including
+ * the full version information. */
+#include "version.h"
+#endif
+
+/**
+ * @defgroup libavc libavcodec
+ * Encoding/Decoding Library
+ *
+ * @{
+ *
+ * @defgroup lavc_decoding Decoding
+ * @{
+ * @}
+ *
+ * @defgroup lavc_encoding Encoding
+ * @{
+ * @}
+ *
+ * @defgroup lavc_codec Codecs
+ * @{
+ * @defgroup lavc_codec_native Native Codecs
+ * @{
+ * @}
+ * @defgroup lavc_codec_wrappers External library wrappers
+ * @{
+ * @}
+ * @defgroup lavc_codec_hwaccel Hardware Accelerators bridge
+ * @{
+ * @}
+ * @}
+ * @defgroup lavc_internal Internal
+ * @{
+ * @}
+ * @}
+ */
+
+/**
+ * @ingroup libavc
+ * @defgroup lavc_encdec send/receive encoding and decoding API overview
+ * @{
+ *
+ * The avcodec_send_packet()/avcodec_receive_frame()/avcodec_send_frame()/
+ * avcodec_receive_packet() functions provide an encode/decode API, which
+ * decouples input and output.
+ *
+ * The API is very similar for encoding/decoding and audio/video, and works as
+ * follows:
+ * - Set up and open the AVCodecContext as usual.
+ * - Send valid input:
+ *   - For decoding, call avcodec_send_packet() to give the decoder raw
+ *     compressed data in an AVPacket.
+ *   - For encoding, call avcodec_send_frame() to give the encoder an AVFrame
+ *     containing uncompressed audio or video.
+ *
+ *   In both cases, it is recommended that AVPackets and AVFrames are
+ *   refcounted, or libavcodec might have to copy the input data. (libavformat
+ *   always returns refcounted AVPackets, and av_frame_get_buffer() allocates
+ *   refcounted AVFrames.)
+ * - Receive output in a loop. Periodically call one of the avcodec_receive_*()
+ *   functions and process their output:
+ *   - For decoding, call avcodec_receive_frame(). On success, it will return
+ *     an AVFrame containing uncompressed audio or video data.
+ *   - For encoding, call avcodec_receive_packet(). On success, it will return
+ *     an AVPacket with a compressed frame.
+ *
+ *   Repeat this call until it returns AVERROR(EAGAIN) or an error. The
+ *   AVERROR(EAGAIN) return value means that new input data is required to
+ *   return new output. In this case, continue with sending input. For each
+ *   input frame/packet, the codec will typically return 1 output frame/packet,
+ *   but it can also be 0 or more than 1.
+ *
+ * At the beginning of decoding or encoding, the codec might accept multiple
+ * input frames/packets without returning a frame, until its internal buffers
+ * are filled. This situation is handled transparently if you follow the steps
+ * outlined above.
+ *
+ * In theory, sending input can result in EAGAIN - this should happen only if
+ * not all output was received. You can use this to structure alternative decode
+ * or encode loops other than the one suggested above. For example, you could
+ * try sending new input on each iteration, and try to receive output if that
+ * returns EAGAIN.
+ *
+ * End of stream situations. These require "flushing" (aka draining) the codec,
+ * as the codec might buffer multiple frames or packets internally for
+ * performance or out of necessity (consider B-frames).
+ * This is handled as follows:
+ * - Instead of valid input, send NULL to the avcodec_send_packet() (decoding)
+ *   or avcodec_send_frame() (encoding) functions. This will enter draining
+ *   mode.
+ * - Call avcodec_receive_frame() (decoding) or avcodec_receive_packet()
+ *   (encoding) in a loop until AVERROR_EOF is returned. The functions will
+ *   not return AVERROR(EAGAIN), unless you forgot to enter draining mode.
+ * - Before decoding can be resumed again, the codec has to be reset with
+ *   avcodec_flush_buffers().
+ *
+ * Using the API as outlined above is highly recommended. But it is also
+ * possible to call functions outside of this rigid schema. For example, you can
+ * call avcodec_send_packet() repeatedly without calling
+ * avcodec_receive_frame(). In this case, avcodec_send_packet() will succeed
+ * until the codec's internal buffer has been filled up (which is typically of
+ * size 1 per output frame, after initial input), and then reject input with
+ * AVERROR(EAGAIN). Once it starts rejecting input, you have no choice but to
+ * read at least some output.
+ *
+ * Not all codecs will follow a rigid and predictable dataflow; the only
+ * guarantee is that an AVERROR(EAGAIN) return value on a send/receive call on
+ * one end implies that a receive/send call on the other end will succeed, or
+ * at least will not fail with AVERROR(EAGAIN). In general, no codec will
+ * permit unlimited buffering of input or output.
+ *
+ * A codec is not allowed to return AVERROR(EAGAIN) for both sending and receiving. This
+ * would be an invalid state, which could put the codec user into an endless
+ * loop. The API has no concept of time either: it cannot happen that trying to
+ * do avcodec_send_packet() results in AVERROR(EAGAIN), but a repeated call 1 second
+ * later accepts the packet (with no other receive/flush API calls involved).
+ * The API is a strict state machine, and the passage of time is not supposed
+ * to influence it. Some timing-dependent behavior might still be deemed
+ * acceptable in certain cases. But it must never result in both send/receive
+ * returning EAGAIN at the same time at any point. It must also absolutely be
+ * avoided that the current state is "unstable" and can "flip-flop" between
+ * the send/receive APIs allowing progress. For example, it's not allowed that
+ * the codec randomly decides that it actually wants to consume a packet now
+ * instead of returning a frame, after it just returned AVERROR(EAGAIN) on an
+ * avcodec_send_packet() call.
+ * @}
+ */
+
+/**
+ * @defgroup lavc_core Core functions/structures.
+ * @ingroup libavc
+ *
+ * Basic definitions, functions for querying libavcodec capabilities,
+ * allocating core structures, etc.
+ * @{
+ */
+
+/**
+ * @ingroup lavc_encoding
+ * minimum encoding buffer size
+ * Used to avoid some checks during header writing.
+ */
+#define AV_INPUT_BUFFER_MIN_SIZE 16384
+
+/**
+ * @ingroup lavc_encoding
+ */
+typedef struct RcOverride{
+    int start_frame;
+    int end_frame;
+    int qscale; // If this is 0 then quality_factor will be used instead.
+    float quality_factor;
+} RcOverride;
+
+/* encoding support
+   These flags can be passed in AVCodecContext.flags before initialization.
+   Note: Not everything is supported yet.
+*/
+
+/**
+ * Allow decoders to produce frames with data planes that are not aligned
+ * to CPU requirements (e.g. due to cropping).
+ */
+#define AV_CODEC_FLAG_UNALIGNED       (1 <<  0)
+/**
+ * Use fixed qscale.
+ */
+#define AV_CODEC_FLAG_QSCALE          (1 <<  1)
+/**
+ * 4 MV per MB allowed / advanced prediction for H.263.
+ */
+#define AV_CODEC_FLAG_4MV             (1 <<  2)
+/**
+ * Output even those frames that might be corrupted.
+ */
+#define AV_CODEC_FLAG_OUTPUT_CORRUPT  (1 <<  3)
+/**
+ * Use qpel MC.
+ */
+#define AV_CODEC_FLAG_QPEL            (1 <<  4)
+/**
+ * Don't output frames whose parameters differ from first
+ * decoded frame in stream.
+ */
+#define AV_CODEC_FLAG_DROPCHANGED     (1 <<  5)
+/**
+ * Request the encoder to output reconstructed frames, i.e.\ frames that would
+ * be produced by decoding the encoded bistream. These frames may be retrieved
+ * by calling avcodec_receive_frame() immediately after a successful call to
+ * avcodec_receive_packet().
+ *
+ * Should only be used with encoders flagged with the
+ * @ref AV_CODEC_CAP_ENCODER_RECON_FRAME capability.
+ */
+#define AV_CODEC_FLAG_RECON_FRAME     (1 <<  6)
+/**
+ * @par decoding
+ * Request the decoder to propagate each packets AVPacket.opaque and
+ * AVPacket.opaque_ref to its corresponding output AVFrame.
+ *
+ * @par encoding:
+ * Request the encoder to propagate each frame's AVFrame.opaque and
+ * AVFrame.opaque_ref values to its corresponding output AVPacket.
+ *
+ * @par
+ * May only be set on encoders that have the
+ * @ref AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE capability flag.
+ *
+ * @note
+ * While in typical cases one input frame produces exactly one output packet
+ * (perhaps after a delay), in general the mapping of frames to packets is
+ * M-to-N, so
+ * - Any number of input frames may be associated with any given output packet.
+ *   This includes zero - e.g. some encoders may output packets that carry only
+ *   metadata about the whole stream.
+ * - A given input frame may be associated with any number of output packets.
+ *   Again this includes zero - e.g. some encoders may drop frames under certain
+ *   conditions.
+ * .
+ * This implies that when using this flag, the caller must NOT assume that
+ * - a given input frame's opaques will necessarily appear on some output packet;
+ * - every output packet will have some non-NULL opaque value.
+ * .
+ * When an output packet contains multiple frames, the opaque values will be
+ * taken from the first of those.
+ *
+ * @note
+ * The converse holds for decoders, with frames and packets switched.
+ */
+#define AV_CODEC_FLAG_COPY_OPAQUE     (1 <<  7)
+/**
+ * Signal to the encoder that the values of AVFrame.duration are valid and
+ * should be used (typically for transferring them to output packets).
+ *
+ * If this flag is not set, frame durations are ignored.
+ */
+#define AV_CODEC_FLAG_FRAME_DURATION  (1 <<  8)
+/**
+ * Use internal 2pass ratecontrol in first pass mode.
+ */
+#define AV_CODEC_FLAG_PASS1           (1 <<  9)
+/**
+ * Use internal 2pass ratecontrol in second pass mode.
+ */
+#define AV_CODEC_FLAG_PASS2           (1 << 10)
+/**
+ * loop filter.
+ */
+#define AV_CODEC_FLAG_LOOP_FILTER     (1 << 11)
+/**
+ * Only decode/encode grayscale.
+ */
+#define AV_CODEC_FLAG_GRAY            (1 << 13)
+/**
+ * error[?] variables will be set during encoding.
+ */
+#define AV_CODEC_FLAG_PSNR            (1 << 15)
+/**
+ * Use interlaced DCT.
+ */
+#define AV_CODEC_FLAG_INTERLACED_DCT  (1 << 18)
+/**
+ * Force low delay.
+ */
+#define AV_CODEC_FLAG_LOW_DELAY       (1 << 19)
+/**
+ * Place global headers in extradata instead of every keyframe.
+ */
+#define AV_CODEC_FLAG_GLOBAL_HEADER   (1 << 22)
+/**
+ * Use only bitexact stuff (except (I)DCT).
+ */
+#define AV_CODEC_FLAG_BITEXACT        (1 << 23)
+/* Fx : Flag for H.263+ extra options */
+/**
+ * H.263 advanced intra coding / MPEG-4 AC prediction
+ */
+#define AV_CODEC_FLAG_AC_PRED         (1 << 24)
+/**
+ * interlaced motion estimation
+ */
+#define AV_CODEC_FLAG_INTERLACED_ME   (1 << 29)
+#define AV_CODEC_FLAG_CLOSED_GOP      (1U << 31)
+
+/**
+ * Allow non spec compliant speedup tricks.
+ */
+#define AV_CODEC_FLAG2_FAST           (1 <<  0)
+/**
+ * Skip bitstream encoding.
+ */
+#define AV_CODEC_FLAG2_NO_OUTPUT      (1 <<  2)
+/**
+ * Place global headers at every keyframe instead of in extradata.
+ */
+#define AV_CODEC_FLAG2_LOCAL_HEADER   (1 <<  3)
+
+/**
+ * Input bitstream might be truncated at a packet boundaries
+ * instead of only at frame boundaries.
+ */
+#define AV_CODEC_FLAG2_CHUNKS         (1 << 15)
+/**
+ * Discard cropping information from SPS.
+ */
+#define AV_CODEC_FLAG2_IGNORE_CROP    (1 << 16)
+
+/**
+ * Show all frames before the first keyframe
+ */
+#define AV_CODEC_FLAG2_SHOW_ALL       (1 << 22)
+/**
+ * Export motion vectors through frame side data
+ */
+#define AV_CODEC_FLAG2_EXPORT_MVS     (1 << 28)
+/**
+ * Do not skip samples and export skip information as frame side data
+ */
+#define AV_CODEC_FLAG2_SKIP_MANUAL    (1 << 29)
+/**
+ * Do not reset ASS ReadOrder field on flush (subtitles decoding)
+ */
+#define AV_CODEC_FLAG2_RO_FLUSH_NOOP  (1 << 30)
+/**
+ * Generate/parse ICC profiles on encode/decode, as appropriate for the type of
+ * file. No effect on codecs which cannot contain embedded ICC profiles, or
+ * when compiled without support for lcms2.
+ */
+#define AV_CODEC_FLAG2_ICC_PROFILES   (1U << 31)
+
+/* Exported side data.
+   These flags can be passed in AVCodecContext.export_side_data before initialization.
+*/
+/**
+ * Export motion vectors through frame side data
+ */
+#define AV_CODEC_EXPORT_DATA_MVS         (1 << 0)
+/**
+ * Export encoder Producer Reference Time through packet side data
+ */
+#define AV_CODEC_EXPORT_DATA_PRFT        (1 << 1)
+/**
+ * Decoding only.
+ * Export the AVVideoEncParams structure through frame side data.
+ */
+#define AV_CODEC_EXPORT_DATA_VIDEO_ENC_PARAMS (1 << 2)
+/**
+ * Decoding only.
+ * Do not apply film grain, export it instead.
+ */
+#define AV_CODEC_EXPORT_DATA_FILM_GRAIN (1 << 3)
+
+/**
+ * The decoder will keep a reference to the frame and may reuse it later.
+ */
+#define AV_GET_BUFFER_FLAG_REF (1 << 0)
+
+/**
+ * The encoder will keep a reference to the packet and may reuse it later.
+ */
+#define AV_GET_ENCODE_BUFFER_FLAG_REF (1 << 0)
+
+struct AVCodecInternal;
+
+/**
+ * main external API structure.
+ * New fields can be added to the end with minor version bumps.
+ * Removal, reordering and changes to existing fields require a major
+ * version bump.
+ * You can use AVOptions (av_opt* / av_set/get*()) to access these fields from user
+ * applications.
+ * The name string for AVOptions options matches the associated command line
+ * parameter name and can be found in libavcodec/options_table.h
+ * The AVOption/command line parameter names differ in some cases from the C
+ * structure field names for historic reasons or brevity.
+ * sizeof(AVCodecContext) must not be used outside libav*.
+ */
+typedef struct AVCodecContext {
+    /**
+     * information on struct for av_log
+     * - set by avcodec_alloc_context3
+     */
+    const AVClass *av_class;
+    int log_level_offset;
+
+    enum AVMediaType codec_type; /* see AVMEDIA_TYPE_xxx */
+    const struct AVCodec  *codec;
+    enum AVCodecID     codec_id; /* see AV_CODEC_ID_xxx */
+
+    /**
+     * fourcc (LSB first, so "ABCD" -> ('D'<<24) + ('C'<<16) + ('B'<<8) + 'A').
+     * This is used to work around some encoder bugs.
+     * A demuxer should set this to what is stored in the field used to identify the codec.
+     * If there are multiple such fields in a container then the demuxer should choose the one
+     * which maximizes the information about the used codec.
+     * If the codec tag field in a container is larger than 32 bits then the demuxer should
+     * remap the longer ID to 32 bits with a table or other structure. Alternatively a new
+     * extra_codec_tag + size could be added but for this a clear advantage must be demonstrated
+     * first.
+     * - encoding: Set by user, if not then the default based on codec_id will be used.
+     * - decoding: Set by user, will be converted to uppercase by libavcodec during init.
+     */
+    unsigned int codec_tag;
+
+    void *priv_data;
+
+    /**
+     * Private context used for internal data.
+     *
+     * Unlike priv_data, this is not codec-specific. It is used in general
+     * libavcodec functions.
+     */
+    struct AVCodecInternal *internal;
+
+    /**
+     * Private data of the user, can be used to carry app specific stuff.
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    void *opaque;
+
+    /**
+     * the average bitrate
+     * - encoding: Set by user; unused for constant quantizer encoding.
+     * - decoding: Set by user, may be overwritten by libavcodec
+     *             if this info is available in the stream
+     */
+    int64_t bit_rate;
+
+    /**
+     * number of bits the bitstream is allowed to diverge from the reference.
+     *           the reference can be CBR (for CBR pass1) or VBR (for pass2)
+     * - encoding: Set by user; unused for constant quantizer encoding.
+     * - decoding: unused
+     */
+    int bit_rate_tolerance;
+
+    /**
+     * Global quality for codecs which cannot change it per frame.
+     * This should be proportional to MPEG-1/2/4 qscale.
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int global_quality;
+
+    /**
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int compression_level;
+#define FF_COMPRESSION_DEFAULT -1
+
+    /**
+     * AV_CODEC_FLAG_*.
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int flags;
+
+    /**
+     * AV_CODEC_FLAG2_*
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int flags2;
+
+    /**
+     * some codecs need / can use extradata like Huffman tables.
+     * MJPEG: Huffman tables
+     * rv10: additional flags
+     * MPEG-4: global headers (they can be in the bitstream or here)
+     * The allocated memory should be AV_INPUT_BUFFER_PADDING_SIZE bytes larger
+     * than extradata_size to avoid problems if it is read with the bitstream reader.
+     * The bytewise contents of extradata must not depend on the architecture or CPU endianness.
+     * Must be allocated with the av_malloc() family of functions.
+     * - encoding: Set/allocated/freed by libavcodec.
+     * - decoding: Set/allocated/freed by user.
+     */
+    uint8_t *extradata;
+    int extradata_size;
+
+    /**
+     * This is the fundamental unit of time (in seconds) in terms
+     * of which frame timestamps are represented. For fixed-fps content,
+     * timebase should be 1/framerate and timestamp increments should be
+     * identically 1.
+     * This often, but not always is the inverse of the frame rate or field rate
+     * for video. 1/time_base is not the average frame rate if the frame rate is not
+     * constant.
+     *
+     * Like containers, elementary streams also can store timestamps, 1/time_base
+     * is the unit in which these timestamps are specified.
+     * As example of such codec time base see ISO/IEC 14496-2:2001(E)
+     * vop_time_increment_resolution and fixed_vop_rate
+     * (fixed_vop_rate == 0 implies that it is different from the framerate)
+     *
+     * - encoding: MUST be set by user.
+     * - decoding: unused.
+     */
+    AVRational time_base;
+
+    /**
+     * For some codecs, the time base is closer to the field rate than the frame rate.
+     * Most notably, H.264 and MPEG-2 specify time_base as half of frame duration
+     * if no telecine is used ...
+     *
+     * Set to time_base ticks per frame. Default 1, e.g., H.264/MPEG-2 set it to 2.
+     */
+    int ticks_per_frame;
+
+    /**
+     * Codec delay.
+     *
+     * Encoding: Number of frames delay there will be from the encoder input to
+     *           the decoder output. (we assume the decoder matches the spec)
+     * Decoding: Number of frames delay in addition to what a standard decoder
+     *           as specified in the spec would produce.
+     *
+     * Video:
+     *   Number of frames the decoded output will be delayed relative to the
+     *   encoded input.
+     *
+     * Audio:
+     *   For encoding, this field is unused (see initial_padding).
+     *
+     *   For decoding, this is the number of samples the decoder needs to
+     *   output before the decoder's output is valid. When seeking, you should
+     *   start decoding this many samples prior to your desired seek point.
+     *
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by libavcodec.
+     */
+    int delay;
+
+
+    /* video only */
+    /**
+     * picture width / height.
+     *
+     * @note Those fields may not match the values of the last
+     * AVFrame output by avcodec_receive_frame() due frame
+     * reordering.
+     *
+     * - encoding: MUST be set by user.
+     * - decoding: May be set by the user before opening the decoder if known e.g.
+     *             from the container. Some decoders will require the dimensions
+     *             to be set by the caller. During decoding, the decoder may
+     *             overwrite those values as required while parsing the data.
+     */
+    int width, height;
+
+    /**
+     * Bitstream width / height, may be different from width/height e.g. when
+     * the decoded frame is cropped before being output or lowres is enabled.
+     *
+     * @note Those field may not match the value of the last
+     * AVFrame output by avcodec_receive_frame() due frame
+     * reordering.
+     *
+     * - encoding: unused
+     * - decoding: May be set by the user before opening the decoder if known
+     *             e.g. from the container. During decoding, the decoder may
+     *             overwrite those values as required while parsing the data.
+     */
+    int coded_width, coded_height;
+
+    /**
+     * the number of pictures in a group of pictures, or 0 for intra_only
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int gop_size;
+
+    /**
+     * Pixel format, see AV_PIX_FMT_xxx.
+     * May be set by the demuxer if known from headers.
+     * May be overridden by the decoder if it knows better.
+     *
+     * @note This field may not match the value of the last
+     * AVFrame output by avcodec_receive_frame() due frame
+     * reordering.
+     *
+     * - encoding: Set by user.
+     * - decoding: Set by user if known, overridden by libavcodec while
+     *             parsing the data.
+     */
+    enum AVPixelFormat pix_fmt;
+
+    /**
+     * If non NULL, 'draw_horiz_band' is called by the libavcodec
+     * decoder to draw a horizontal band. It improves cache usage. Not
+     * all codecs can do that. You must check the codec capabilities
+     * beforehand.
+     * When multithreading is used, it may be called from multiple threads
+     * at the same time; threads might draw different parts of the same AVFrame,
+     * or multiple AVFrames, and there is no guarantee that slices will be drawn
+     * in order.
+     * The function is also used by hardware acceleration APIs.
+     * It is called at least once during frame decoding to pass
+     * the data needed for hardware render.
+     * In that mode instead of pixel data, AVFrame points to
+     * a structure specific to the acceleration API. The application
+     * reads the structure and can change some fields to indicate progress
+     * or mark state.
+     * - encoding: unused
+     * - decoding: Set by user.
+     * @param height the height of the slice
+     * @param y the y position of the slice
+     * @param type 1->top field, 2->bottom field, 3->frame
+     * @param offset offset into the AVFrame.data from which the slice should be read
+     */
+    void (*draw_horiz_band)(struct AVCodecContext *s,
+                            const AVFrame *src, int offset[AV_NUM_DATA_POINTERS],
+                            int y, int type, int height);
+
+    /**
+     * Callback to negotiate the pixel format. Decoding only, may be set by the
+     * caller before avcodec_open2().
+     *
+     * Called by some decoders to select the pixel format that will be used for
+     * the output frames. This is mainly used to set up hardware acceleration,
+     * then the provided format list contains the corresponding hwaccel pixel
+     * formats alongside the "software" one. The software pixel format may also
+     * be retrieved from \ref sw_pix_fmt.
+     *
+     * This callback will be called when the coded frame properties (such as
+     * resolution, pixel format, etc.) change and more than one output format is
+     * supported for those new properties. If a hardware pixel format is chosen
+     * and initialization for it fails, the callback may be called again
+     * immediately.
+     *
+     * This callback may be called from different threads if the decoder is
+     * multi-threaded, but not from more than one thread simultaneously.
+     *
+     * @param fmt list of formats which may be used in the current
+     *            configuration, terminated by AV_PIX_FMT_NONE.
+     * @warning Behavior is undefined if the callback returns a value other
+     *          than one of the formats in fmt or AV_PIX_FMT_NONE.
+     * @return the chosen format or AV_PIX_FMT_NONE
+     */
+    enum AVPixelFormat (*get_format)(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
+
+    /**
+     * maximum number of B-frames between non-B-frames
+     * Note: The output will be delayed by max_b_frames+1 relative to the input.
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int max_b_frames;
+
+    /**
+     * qscale factor between IP and B-frames
+     * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
+     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float b_quant_factor;
+
+    /**
+     * qscale offset between IP and B-frames
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float b_quant_offset;
+
+    /**
+     * Size of the frame reordering buffer in the decoder.
+     * For MPEG-2 it is 1 IPB or 0 low delay IP.
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by libavcodec.
+     */
+    int has_b_frames;
+
+    /**
+     * qscale factor between P- and I-frames
+     * If > 0 then the last P-frame quantizer will be used (q = lastp_q * factor + offset).
+     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float i_quant_factor;
+
+    /**
+     * qscale offset between P and I-frames
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float i_quant_offset;
+
+    /**
+     * luminance masking (0-> disabled)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float lumi_masking;
+
+    /**
+     * temporary complexity masking (0-> disabled)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float temporal_cplx_masking;
+
+    /**
+     * spatial complexity masking (0-> disabled)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float spatial_cplx_masking;
+
+    /**
+     * p block masking (0-> disabled)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float p_masking;
+
+    /**
+     * darkness masking (0-> disabled)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    float dark_masking;
+
+    /**
+     * slice count
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by user (or 0).
+     */
+    int slice_count;
+
+    /**
+     * slice offsets in the frame in bytes
+     * - encoding: Set/allocated by libavcodec.
+     * - decoding: Set/allocated by user (or NULL).
+     */
+    int *slice_offset;
+
+    /**
+     * sample aspect ratio (0 if unknown)
+     * That is the width of a pixel divided by the height of the pixel.
+     * Numerator and denominator must be relatively prime and smaller than 256 for some video standards.
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec.
+     */
+    AVRational sample_aspect_ratio;
+
+    /**
+     * motion estimation comparison function
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int me_cmp;
+    /**
+     * subpixel motion estimation comparison function
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int me_sub_cmp;
+    /**
+     * macroblock comparison function (not supported yet)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int mb_cmp;
+    /**
+     * interlaced DCT comparison function
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int ildct_cmp;
+#define FF_CMP_SAD          0
+#define FF_CMP_SSE          1
+#define FF_CMP_SATD         2
+#define FF_CMP_DCT          3
+#define FF_CMP_PSNR         4
+#define FF_CMP_BIT          5
+#define FF_CMP_RD           6
+#define FF_CMP_ZERO         7
+#define FF_CMP_VSAD         8
+#define FF_CMP_VSSE         9
+#define FF_CMP_NSSE         10
+#define FF_CMP_W53          11
+#define FF_CMP_W97          12
+#define FF_CMP_DCTMAX       13
+#define FF_CMP_DCT264       14
+#define FF_CMP_MEDIAN_SAD   15
+#define FF_CMP_CHROMA       256
+
+    /**
+     * ME diamond size & shape
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int dia_size;
+
+    /**
+     * amount of previous MV predictors (2a+1 x 2a+1 square)
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int last_predictor_count;
+
+    /**
+     * motion estimation prepass comparison function
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int me_pre_cmp;
+
+    /**
+     * ME prepass diamond size & shape
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int pre_dia_size;
+
+    /**
+     * subpel ME quality
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int me_subpel_quality;
+
+    /**
+     * maximum motion estimation search range in subpel units
+     * If 0 then no limit.
+     *
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int me_range;
+
+    /**
+     * slice flags
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    int slice_flags;
+#define SLICE_FLAG_CODED_ORDER    0x0001 ///< draw_horiz_band() is called in coded order instead of display
+#define SLICE_FLAG_ALLOW_FIELD    0x0002 ///< allow draw_horiz_band() with field slices (MPEG-2 field pics)
+#define SLICE_FLAG_ALLOW_PLANE    0x0004 ///< allow draw_horiz_band() with 1 component at a time (SVQ1)
+
+    /**
+     * macroblock decision mode
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int mb_decision;
+#define FF_MB_DECISION_SIMPLE 0        ///< uses mb_cmp
+#define FF_MB_DECISION_BITS   1        ///< chooses the one which needs the fewest bits
+#define FF_MB_DECISION_RD     2        ///< rate distortion
+
+    /**
+     * custom intra quantization matrix
+     * Must be allocated with the av_malloc() family of functions, and will be freed in
+     * avcodec_free_context().
+     * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
+     * - decoding: Set/allocated/freed by libavcodec.
+     */
+    uint16_t *intra_matrix;
+
+    /**
+     * custom inter quantization matrix
+     * Must be allocated with the av_malloc() family of functions, and will be freed in
+     * avcodec_free_context().
+     * - encoding: Set/allocated by user, freed by libavcodec. Can be NULL.
+     * - decoding: Set/allocated/freed by libavcodec.
+     */
+    uint16_t *inter_matrix;
+
+    /**
+     * precision of the intra DC coefficient - 8
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec
+     */
+    int intra_dc_precision;
+
+    /**
+     * Number of macroblock rows at the top which are skipped.
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    int skip_top;
+
+    /**
+     * Number of macroblock rows at the bottom which are skipped.
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    int skip_bottom;
+
+    /**
+     * minimum MB Lagrange multiplier
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int mb_lmin;
+
+    /**
+     * maximum MB Lagrange multiplier
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int mb_lmax;
+
+    /**
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int bidir_refine;
+
+    /**
+     * minimum GOP size
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int keyint_min;
+
+    /**
+     * number of reference frames
+     * - encoding: Set by user.
+     * - decoding: Set by lavc.
+     */
+    int refs;
+
+    /**
+     * Note: Value depends upon the compare function used for fullpel ME.
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int mv0_threshold;
+
+    /**
+     * Chromaticity coordinates of the source primaries.
+     * - encoding: Set by user
+     * - decoding: Set by libavcodec
+     */
+    enum AVColorPrimaries color_primaries;
+
+    /**
+     * Color Transfer Characteristic.
+     * - encoding: Set by user
+     * - decoding: Set by libavcodec
+     */
+    enum AVColorTransferCharacteristic color_trc;
+
+    /**
+     * YUV colorspace type.
+     * - encoding: Set by user
+     * - decoding: Set by libavcodec
+     */
+    enum AVColorSpace colorspace;
+
+    /**
+     * MPEG vs JPEG YUV range.
+     * - encoding: Set by user
+     * - decoding: Set by libavcodec
+     */
+    enum AVColorRange color_range;
+
+    /**
+     * This defines the location of chroma samples.
+     * - encoding: Set by user
+     * - decoding: Set by libavcodec
+     */
+    enum AVChromaLocation chroma_sample_location;
+
+    /**
+     * Number of slices.
+     * Indicates number of picture subdivisions. Used for parallelized
+     * decoding.
+     * - encoding: Set by user
+     * - decoding: unused
+     */
+    int slices;
+
+    /** Field order
+     * - encoding: set by libavcodec
+     * - decoding: Set by user.
+     */
+    enum AVFieldOrder field_order;
+
+    /* audio only */
+    int sample_rate; ///< samples per second
+
+#if FF_API_OLD_CHANNEL_LAYOUT
+    /**
+     * number of audio channels
+     * @deprecated use ch_layout.nb_channels
+     */
+    attribute_deprecated
+    int channels;
+#endif
+
+    /**
+     * audio sample format
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec.
+     */
+    enum AVSampleFormat sample_fmt;  ///< sample format
+
+    /* The following data should not be initialized. */
+    /**
+     * Number of samples per channel in an audio frame.
+     *
+     * - encoding: set by libavcodec in avcodec_open2(). Each submitted frame
+     *   except the last must contain exactly frame_size samples per channel.
+     *   May be 0 when the codec has AV_CODEC_CAP_VARIABLE_FRAME_SIZE set, then the
+     *   frame size is not restricted.
+     * - decoding: may be set by some decoders to indicate constant frame size
+     */
+    int frame_size;
+
+#if FF_API_AVCTX_FRAME_NUMBER
+    /**
+     * Frame counter, set by libavcodec.
+     *
+     * - decoding: total number of frames returned from the decoder so far.
+     * - encoding: total number of frames passed to the encoder so far.
+     *
+     *   @note the counter is not incremented if encoding/decoding resulted in
+     *   an error.
+     *   @deprecated use frame_num instead
+     */
+    attribute_deprecated
+    int frame_number;
+#endif
+
+    /**
+     * number of bytes per packet if constant and known or 0
+     * Used by some WAV based audio codecs.
+     */
+    int block_align;
+
+    /**
+     * Audio cutoff bandwidth (0 means "automatic")
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int cutoff;
+
+#if FF_API_OLD_CHANNEL_LAYOUT
+    /**
+     * Audio channel layout.
+     * - encoding: set by user.
+     * - decoding: set by user, may be overwritten by libavcodec.
+     * @deprecated use ch_layout
+     */
+    attribute_deprecated
+    uint64_t channel_layout;
+
+    /**
+     * Request decoder to use this channel layout if it can (0 for default)
+     * - encoding: unused
+     * - decoding: Set by user.
+     * @deprecated use "downmix" codec private option
+     */
+    attribute_deprecated
+    uint64_t request_channel_layout;
+#endif
+
+    /**
+     * Type of service that the audio stream conveys.
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec.
+     */
+    enum AVAudioServiceType audio_service_type;
+
+    /**
+     * desired sample format
+     * - encoding: Not used.
+     * - decoding: Set by user.
+     * Decoder will decode to this format if it can.
+     */
+    enum AVSampleFormat request_sample_fmt;
+
+    /**
+     * This callback is called at the beginning of each frame to get data
+     * buffer(s) for it. There may be one contiguous buffer for all the data or
+     * there may be a buffer per each data plane or anything in between. What
+     * this means is, you may set however many entries in buf[] you feel necessary.
+     * Each buffer must be reference-counted using the AVBuffer API (see description
+     * of buf[] below).
+     *
+     * The following fields will be set in the frame before this callback is
+     * called:
+     * - format
+     * - width, height (video only)
+     * - sample_rate, channel_layout, nb_samples (audio only)
+     * Their values may differ from the corresponding values in
+     * AVCodecContext. This callback must use the frame values, not the codec
+     * context values, to calculate the required buffer size.
+     *
+     * This callback must fill the following fields in the frame:
+     * - data[]
+     * - linesize[]
+     * - extended_data:
+     *   * if the data is planar audio with more than 8 channels, then this
+     *     callback must allocate and fill extended_data to contain all pointers
+     *     to all data planes. data[] must hold as many pointers as it can.
+     *     extended_data must be allocated with av_malloc() and will be freed in
+     *     av_frame_unref().
+     *   * otherwise extended_data must point to data
+     * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
+     *   the frame's data and extended_data pointers must be contained in these. That
+     *   is, one AVBufferRef for each allocated chunk of memory, not necessarily one
+     *   AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
+     *   and av_buffer_ref().
+     * - extended_buf and nb_extended_buf must be allocated with av_malloc() by
+     *   this callback and filled with the extra buffers if there are more
+     *   buffers than buf[] can hold. extended_buf will be freed in
+     *   av_frame_unref().
+     *
+     * If AV_CODEC_CAP_DR1 is not set then get_buffer2() must call
+     * avcodec_default_get_buffer2() instead of providing buffers allocated by
+     * some other means.
+     *
+     * Each data plane must be aligned to the maximum required by the target
+     * CPU.
+     *
+     * @see avcodec_default_get_buffer2()
+     *
+     * Video:
+     *
+     * If AV_GET_BUFFER_FLAG_REF is set in flags then the frame may be reused
+     * (read and/or written to if it is writable) later by libavcodec.
+     *
+     * avcodec_align_dimensions2() should be used to find the required width and
+     * height, as they normally need to be rounded up to the next multiple of 16.
+     *
+     * Some decoders do not support linesizes changing between frames.
+     *
+     * If frame multithreading is used, this callback may be called from a
+     * different thread, but not from more than one at once. Does not need to be
+     * reentrant.
+     *
+     * @see avcodec_align_dimensions2()
+     *
+     * Audio:
+     *
+     * Decoders request a buffer of a particular size by setting
+     * AVFrame.nb_samples prior to calling get_buffer2(). The decoder may,
+     * however, utilize only part of the buffer by setting AVFrame.nb_samples
+     * to a smaller value in the output frame.
+     *
+     * As a convenience, av_samples_get_buffer_size() and
+     * av_samples_fill_arrays() in libavutil may be used by custom get_buffer2()
+     * functions to find the required data size and to fill data pointers and
+     * linesize. In AVFrame.linesize, only linesize[0] may be set for audio
+     * since all planes must be the same size.
+     *
+     * @see av_samples_get_buffer_size(), av_samples_fill_arrays()
+     *
+     * - encoding: unused
+     * - decoding: Set by libavcodec, user can override.
+     */
+    int (*get_buffer2)(struct AVCodecContext *s, AVFrame *frame, int flags);
+
+    /* - encoding parameters */
+    float qcompress;  ///< amount of qscale change between easy & hard scenes (0.0-1.0)
+    float qblur;      ///< amount of qscale smoothing over time (0.0-1.0)
+
+    /**
+     * minimum quantizer
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int qmin;
+
+    /**
+     * maximum quantizer
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int qmax;
+
+    /**
+     * maximum quantizer difference between frames
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int max_qdiff;
+
+    /**
+     * decoder bitstream buffer size
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int rc_buffer_size;
+
+    /**
+     * ratecontrol override, see RcOverride
+     * - encoding: Allocated/set/freed by user.
+     * - decoding: unused
+     */
+    int rc_override_count;
+    RcOverride *rc_override;
+
+    /**
+     * maximum bitrate
+     * - encoding: Set by user.
+     * - decoding: Set by user, may be overwritten by libavcodec.
+     */
+    int64_t rc_max_rate;
+
+    /**
+     * minimum bitrate
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int64_t rc_min_rate;
+
+    /**
+     * Ratecontrol attempt to use, at maximum, <value> of what can be used without an underflow.
+     * - encoding: Set by user.
+     * - decoding: unused.
+     */
+    float rc_max_available_vbv_use;
+
+    /**
+     * Ratecontrol attempt to use, at least, <value> times the amount needed to prevent a vbv overflow.
+     * - encoding: Set by user.
+     * - decoding: unused.
+     */
+    float rc_min_vbv_overflow_use;
+
+    /**
+     * Number of bits which should be loaded into the rc buffer before decoding starts.
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int rc_initial_buffer_occupancy;
+
+    /**
+     * trellis RD quantization
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int trellis;
+
+    /**
+     * pass1 encoding statistics output buffer
+     * - encoding: Set by libavcodec.
+     * - decoding: unused
+     */
+    char *stats_out;
+
+    /**
+     * pass2 encoding statistics input buffer
+     * Concatenated stuff from stats_out of pass1 should be placed here.
+     * - encoding: Allocated/set/freed by user.
+     * - decoding: unused
+     */
+    char *stats_in;
+
+    /**
+     * Work around bugs in encoders which sometimes cannot be detected automatically.
+     * - encoding: Set by user
+     * - decoding: Set by user
+     */
+    int workaround_bugs;
+#define FF_BUG_AUTODETECT       1  ///< autodetection
+#define FF_BUG_XVID_ILACE       4
+#define FF_BUG_UMP4             8
+#define FF_BUG_NO_PADDING       16
+#define FF_BUG_AMV              32
+#define FF_BUG_QPEL_CHROMA      64
+#define FF_BUG_STD_QPEL         128
+#define FF_BUG_QPEL_CHROMA2     256
+#define FF_BUG_DIRECT_BLOCKSIZE 512
+#define FF_BUG_EDGE             1024
+#define FF_BUG_HPEL_CHROMA      2048
+#define FF_BUG_DC_CLIP          4096
+#define FF_BUG_MS               8192 ///< Work around various bugs in Microsoft's broken decoders.
+#define FF_BUG_TRUNCATED       16384
+#define FF_BUG_IEDGE           32768
+
+    /**
+     * strictly follow the standard (MPEG-4, ...).
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     * Setting this to STRICT or higher means the encoder and decoder will
+     * generally do stupid things, whereas setting it to unofficial or lower
+     * will mean the encoder might produce output that is not supported by all
+     * spec-compliant decoders. Decoders don't differentiate between normal,
+     * unofficial and experimental (that is, they always try to decode things
+     * when they can) unless they are explicitly asked to behave stupidly
+     * (=strictly conform to the specs)
+     * This may only be set to one of the FF_COMPLIANCE_* values in defs.h.
+     */
+    int strict_std_compliance;
+
+    /**
+     * error concealment flags
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    int error_concealment;
+#define FF_EC_GUESS_MVS   1
+#define FF_EC_DEBLOCK     2
+#define FF_EC_FAVOR_INTER 256
+
+    /**
+     * debug
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int debug;
+#define FF_DEBUG_PICT_INFO   1
+#define FF_DEBUG_RC          2
+#define FF_DEBUG_BITSTREAM   4
+#define FF_DEBUG_MB_TYPE     8
+#define FF_DEBUG_QP          16
+#define FF_DEBUG_DCT_COEFF   0x00000040
+#define FF_DEBUG_SKIP        0x00000080
+#define FF_DEBUG_STARTCODE   0x00000100
+#define FF_DEBUG_ER          0x00000400
+#define FF_DEBUG_MMCO        0x00000800
+#define FF_DEBUG_BUGS        0x00001000
+#define FF_DEBUG_BUFFERS     0x00008000
+#define FF_DEBUG_THREADS     0x00010000
+#define FF_DEBUG_GREEN_MD    0x00800000
+#define FF_DEBUG_NOMC        0x01000000
+
+    /**
+     * Error recognition; may misdetect some more or less valid parts as errors.
+     * This is a bitfield of the AV_EF_* values defined in defs.h.
+     *
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int err_recognition;
+
+#if FF_API_REORDERED_OPAQUE
+    /**
+     * opaque 64-bit number (generally a PTS) that will be reordered and
+     * output in AVFrame.reordered_opaque
+     * - encoding: Set by libavcodec to the reordered_opaque of the input
+     *             frame corresponding to the last returned packet. Only
+     *             supported by encoders with the
+     *             AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE capability.
+     * - decoding: Set by user.
+     *
+     * @deprecated Use AV_CODEC_FLAG_COPY_OPAQUE instead
+     */
+    attribute_deprecated
+    int64_t reordered_opaque;
+#endif
+
+    /**
+     * Hardware accelerator in use
+     * - encoding: unused.
+     * - decoding: Set by libavcodec
+     */
+    const struct AVHWAccel *hwaccel;
+
+    /**
+     * Legacy hardware accelerator context.
+     *
+     * For some hardware acceleration methods, the caller may use this field to
+     * signal hwaccel-specific data to the codec. The struct pointed to by this
+     * pointer is hwaccel-dependent and defined in the respective header. Please
+     * refer to the FFmpeg HW accelerator documentation to know how to fill
+     * this.
+     *
+     * In most cases this field is optional - the necessary information may also
+     * be provided to libavcodec through @ref hw_frames_ctx or @ref
+     * hw_device_ctx (see avcodec_get_hw_config()). However, in some cases it
+     * may be the only method of signalling some (optional) information.
+     *
+     * The struct and its contents are owned by the caller.
+     *
+     * - encoding: May be set by the caller before avcodec_open2(). Must remain
+     *             valid until avcodec_free_context().
+     * - decoding: May be set by the caller in the get_format() callback.
+     *             Must remain valid until the next get_format() call,
+     *             or avcodec_free_context() (whichever comes first).
+     */
+    void *hwaccel_context;
+
+    /**
+     * error
+     * - encoding: Set by libavcodec if flags & AV_CODEC_FLAG_PSNR.
+     * - decoding: unused
+     */
+    uint64_t error[AV_NUM_DATA_POINTERS];
+
+    /**
+     * DCT algorithm, see FF_DCT_* below
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+    int dct_algo;
+#define FF_DCT_AUTO    0
+#define FF_DCT_FASTINT 1
+#define FF_DCT_INT     2
+#define FF_DCT_MMX     3
+#define FF_DCT_ALTIVEC 5
+#define FF_DCT_FAAN    6
+
+    /**
+     * IDCT algorithm, see FF_IDCT_* below.
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int idct_algo;
+#define FF_IDCT_AUTO          0
+#define FF_IDCT_INT           1
+#define FF_IDCT_SIMPLE        2
+#define FF_IDCT_SIMPLEMMX     3
+#define FF_IDCT_ARM           7
+#define FF_IDCT_ALTIVEC       8
+#define FF_IDCT_SIMPLEARM     10
+#define FF_IDCT_XVID          14
+#define FF_IDCT_SIMPLEARMV5TE 16
+#define FF_IDCT_SIMPLEARMV6   17
+#define FF_IDCT_FAAN          20
+#define FF_IDCT_SIMPLENEON    22
+#if FF_API_IDCT_NONE
+// formerly used by xvmc
+#define FF_IDCT_NONE          24
+#endif
+#define FF_IDCT_SIMPLEAUTO    128
+
+    /**
+     * bits per sample/pixel from the demuxer (needed for huffyuv).
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by user.
+     */
+     int bits_per_coded_sample;
+
+    /**
+     * Bits per sample/pixel of internal libavcodec pixel/sample format.
+     * - encoding: set by user.
+     * - decoding: set by libavcodec.
+     */
+    int bits_per_raw_sample;
+
+    /**
+     * low resolution decoding, 1-> 1/2 size, 2->1/4 size
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+     int lowres;
+
+    /**
+     * thread count
+     * is used to decide how many independent tasks should be passed to execute()
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    int thread_count;
+
+    /**
+     * Which multithreading methods to use.
+     * Use of FF_THREAD_FRAME will increase decoding delay by one frame per thread,
+     * so clients which cannot provide future frames should not use it.
+     *
+     * - encoding: Set by user, otherwise the default is used.
+     * - decoding: Set by user, otherwise the default is used.
+     */
+    int thread_type;
+#define FF_THREAD_FRAME   1 ///< Decode more than one frame at once
+#define FF_THREAD_SLICE   2 ///< Decode more than one part of a single frame at once
+
+    /**
+     * Which multithreading methods are in use by the codec.
+     * - encoding: Set by libavcodec.
+     * - decoding: Set by libavcodec.
+     */
+    int active_thread_type;
+
+    /**
+     * The codec may call this to execute several independent things.
+     * It will return only after finishing all tasks.
+     * The user may replace this with some multithreaded implementation,
+     * the default implementation will execute the parts serially.
+     * @param count the number of things to execute
+     * - encoding: Set by libavcodec, user can override.
+     * - decoding: Set by libavcodec, user can override.
+     */
+    int (*execute)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg), void *arg2, int *ret, int count, int size);
+
+    /**
+     * The codec may call this to execute several independent things.
+     * It will return only after finishing all tasks.
+     * The user may replace this with some multithreaded implementation,
+     * the default implementation will execute the parts serially.
+     * @param c context passed also to func
+     * @param count the number of things to execute
+     * @param arg2 argument passed unchanged to func
+     * @param ret return values of executed functions, must have space for "count" values. May be NULL.
+     * @param func function that will be called count times, with jobnr from 0 to count-1.
+     *             threadnr will be in the range 0 to c->thread_count-1 < MAX_THREADS and so that no
+     *             two instances of func executing at the same time will have the same threadnr.
+     * @return always 0 currently, but code should handle a future improvement where when any call to func
+     *         returns < 0 no further calls to func may be done and < 0 is returned.
+     * - encoding: Set by libavcodec, user can override.
+     * - decoding: Set by libavcodec, user can override.
+     */
+    int (*execute2)(struct AVCodecContext *c, int (*func)(struct AVCodecContext *c2, void *arg, int jobnr, int threadnr), void *arg2, int *ret, int count);
+
+    /**
+     * noise vs. sse weight for the nsse comparison function
+     * - encoding: Set by user.
+     * - decoding: unused
+     */
+     int nsse_weight;
+
+    /**
+     * profile
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec.
+     */
+     int profile;
+#define FF_PROFILE_UNKNOWN -99
+#define FF_PROFILE_RESERVED -100
+
+#define FF_PROFILE_AAC_MAIN 0
+#define FF_PROFILE_AAC_LOW  1
+#define FF_PROFILE_AAC_SSR  2
+#define FF_PROFILE_AAC_LTP  3
+#define FF_PROFILE_AAC_HE   4
+#define FF_PROFILE_AAC_HE_V2 28
+#define FF_PROFILE_AAC_LD   22
+#define FF_PROFILE_AAC_ELD  38
+#define FF_PROFILE_MPEG2_AAC_LOW 128
+#define FF_PROFILE_MPEG2_AAC_HE  131
+
+#define FF_PROFILE_DNXHD         0
+#define FF_PROFILE_DNXHR_LB      1
+#define FF_PROFILE_DNXHR_SQ      2
+#define FF_PROFILE_DNXHR_HQ      3
+#define FF_PROFILE_DNXHR_HQX     4
+#define FF_PROFILE_DNXHR_444     5
+
+#define FF_PROFILE_DTS         20
+#define FF_PROFILE_DTS_ES      30
+#define FF_PROFILE_DTS_96_24   40
+#define FF_PROFILE_DTS_HD_HRA  50
+#define FF_PROFILE_DTS_HD_MA   60
+#define FF_PROFILE_DTS_EXPRESS 70
+
+#define FF_PROFILE_MPEG2_422    0
+#define FF_PROFILE_MPEG2_HIGH   1
+#define FF_PROFILE_MPEG2_SS     2
+#define FF_PROFILE_MPEG2_SNR_SCALABLE  3
+#define FF_PROFILE_MPEG2_MAIN   4
+#define FF_PROFILE_MPEG2_SIMPLE 5
+
+#define FF_PROFILE_H264_CONSTRAINED  (1<<9)  // 8+1; constraint_set1_flag
+#define FF_PROFILE_H264_INTRA        (1<<11) // 8+3; constraint_set3_flag
+
+#define FF_PROFILE_H264_BASELINE             66
+#define FF_PROFILE_H264_CONSTRAINED_BASELINE (66|FF_PROFILE_H264_CONSTRAINED)
+#define FF_PROFILE_H264_MAIN                 77
+#define FF_PROFILE_H264_EXTENDED             88
+#define FF_PROFILE_H264_HIGH                 100
+#define FF_PROFILE_H264_HIGH_10              110
+#define FF_PROFILE_H264_HIGH_10_INTRA        (110|FF_PROFILE_H264_INTRA)
+#define FF_PROFILE_H264_MULTIVIEW_HIGH       118
+#define FF_PROFILE_H264_HIGH_422             122
+#define FF_PROFILE_H264_HIGH_422_INTRA       (122|FF_PROFILE_H264_INTRA)
+#define FF_PROFILE_H264_STEREO_HIGH          128
+#define FF_PROFILE_H264_HIGH_444             144
+#define FF_PROFILE_H264_HIGH_444_PREDICTIVE  244
+#define FF_PROFILE_H264_HIGH_444_INTRA       (244|FF_PROFILE_H264_INTRA)
+#define FF_PROFILE_H264_CAVLC_444            44
+
+#define FF_PROFILE_VC1_SIMPLE   0
+#define FF_PROFILE_VC1_MAIN     1
+#define FF_PROFILE_VC1_COMPLEX  2
+#define FF_PROFILE_VC1_ADVANCED 3
+
+#define FF_PROFILE_MPEG4_SIMPLE                     0
+#define FF_PROFILE_MPEG4_SIMPLE_SCALABLE            1
+#define FF_PROFILE_MPEG4_CORE                       2
+#define FF_PROFILE_MPEG4_MAIN                       3
+#define FF_PROFILE_MPEG4_N_BIT                      4
+#define FF_PROFILE_MPEG4_SCALABLE_TEXTURE           5
+#define FF_PROFILE_MPEG4_SIMPLE_FACE_ANIMATION      6
+#define FF_PROFILE_MPEG4_BASIC_ANIMATED_TEXTURE     7
+#define FF_PROFILE_MPEG4_HYBRID                     8
+#define FF_PROFILE_MPEG4_ADVANCED_REAL_TIME         9
+#define FF_PROFILE_MPEG4_CORE_SCALABLE             10
+#define FF_PROFILE_MPEG4_ADVANCED_CODING           11
+#define FF_PROFILE_MPEG4_ADVANCED_CORE             12
+#define FF_PROFILE_MPEG4_ADVANCED_SCALABLE_TEXTURE 13
+#define FF_PROFILE_MPEG4_SIMPLE_STUDIO             14
+#define FF_PROFILE_MPEG4_ADVANCED_SIMPLE           15
+
+#define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_0   1
+#define FF_PROFILE_JPEG2000_CSTREAM_RESTRICTION_1   2
+#define FF_PROFILE_JPEG2000_CSTREAM_NO_RESTRICTION  32768
+#define FF_PROFILE_JPEG2000_DCINEMA_2K              3
+#define FF_PROFILE_JPEG2000_DCINEMA_4K              4
+
+#define FF_PROFILE_VP9_0                            0
+#define FF_PROFILE_VP9_1                            1
+#define FF_PROFILE_VP9_2                            2
+#define FF_PROFILE_VP9_3                            3
+
+#define FF_PROFILE_HEVC_MAIN                        1
+#define FF_PROFILE_HEVC_MAIN_10                     2
+#define FF_PROFILE_HEVC_MAIN_STILL_PICTURE          3
+#define FF_PROFILE_HEVC_REXT                        4
+#define FF_PROFILE_HEVC_SCC                         9
+
+#define FF_PROFILE_VVC_MAIN_10                      1
+#define FF_PROFILE_VVC_MAIN_10_444                 33
+
+#define FF_PROFILE_AV1_MAIN                         0
+#define FF_PROFILE_AV1_HIGH                         1
+#define FF_PROFILE_AV1_PROFESSIONAL                 2
+
+#define FF_PROFILE_MJPEG_HUFFMAN_BASELINE_DCT            0xc0
+#define FF_PROFILE_MJPEG_HUFFMAN_EXTENDED_SEQUENTIAL_DCT 0xc1
+#define FF_PROFILE_MJPEG_HUFFMAN_PROGRESSIVE_DCT         0xc2
+#define FF_PROFILE_MJPEG_HUFFMAN_LOSSLESS                0xc3
+#define FF_PROFILE_MJPEG_JPEG_LS                         0xf7
+
+#define FF_PROFILE_SBC_MSBC                         1
+
+#define FF_PROFILE_PRORES_PROXY     0
+#define FF_PROFILE_PRORES_LT        1
+#define FF_PROFILE_PRORES_STANDARD  2
+#define FF_PROFILE_PRORES_HQ        3
+#define FF_PROFILE_PRORES_4444      4
+#define FF_PROFILE_PRORES_XQ        5
+
+#define FF_PROFILE_ARIB_PROFILE_A 0
+#define FF_PROFILE_ARIB_PROFILE_C 1
+
+#define FF_PROFILE_KLVA_SYNC 0
+#define FF_PROFILE_KLVA_ASYNC 1
+
+    /**
+     * level
+     * - encoding: Set by user.
+     * - decoding: Set by libavcodec.
+     */
+     int level;
+#define FF_LEVEL_UNKNOWN -99
+
+    /**
+     * Skip loop filtering for selected frames.
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    enum AVDiscard skip_loop_filter;
+
+    /**
+     * Skip IDCT/dequantization for selected frames.
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    enum AVDiscard skip_idct;
+
+    /**
+     * Skip decoding for selected frames.
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    enum AVDiscard skip_frame;
+
+    /**
+     * Header containing style information for text subtitles.
+     * For SUBTITLE_ASS subtitle type, it should contain the whole ASS
+     * [Script Info] and [V4+ Styles] section, plus the [Events] line and
+     * the Format line following. It shouldn't include any Dialogue line.
+     * - encoding: Set/allocated/freed by user (before avcodec_open2())
+     * - decoding: Set/allocated/freed by libavcodec (by avcodec_open2())
+     */
+    uint8_t *subtitle_header;
+    int subtitle_header_size;
+
+    /**
+     * Audio only. The number of "priming" samples (padding) inserted by the
+     * encoder at the beginning of the audio. I.e. this number of leading
+     * decoded samples must be discarded by the caller to get the original audio
+     * without leading padding.
+     *
+     * - decoding: unused
+     * - encoding: Set by libavcodec. The timestamps on the output packets are
+     *             adjusted by the encoder so that they always refer to the
+     *             first sample of the data actually contained in the packet,
+     *             including any added padding.  E.g. if the timebase is
+     *             1/samplerate and the timestamp of the first input sample is
+     *             0, the timestamp of the first output packet will be
+     *             -initial_padding.
+     */
+    int initial_padding;
+
+    /**
+     * - decoding: For codecs that store a framerate value in the compressed
+     *             bitstream, the decoder may export it here. { 0, 1} when
+     *             unknown.
+     * - encoding: May be used to signal the framerate of CFR content to an
+     *             encoder.
+     */
+    AVRational framerate;
+
+    /**
+     * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
+     * - encoding: unused.
+     * - decoding: Set by libavcodec before calling get_format()
+     */
+    enum AVPixelFormat sw_pix_fmt;
+
+    /**
+     * Timebase in which pkt_dts/pts and AVPacket.dts/pts are.
+     * - encoding unused.
+     * - decoding set by user.
+     */
+    AVRational pkt_timebase;
+
+    /**
+     * AVCodecDescriptor
+     * - encoding: unused.
+     * - decoding: set by libavcodec.
+     */
+    const AVCodecDescriptor *codec_descriptor;
+
+    /**
+     * Current statistics for PTS correction.
+     * - decoding: maintained and used by libavcodec, not intended to be used by user apps
+     * - encoding: unused
+     */
+    int64_t pts_correction_num_faulty_pts; /// Number of incorrect PTS values so far
+    int64_t pts_correction_num_faulty_dts; /// Number of incorrect DTS values so far
+    int64_t pts_correction_last_pts;       /// PTS of the last frame
+    int64_t pts_correction_last_dts;       /// DTS of the last frame
+
+    /**
+     * Character encoding of the input subtitles file.
+     * - decoding: set by user
+     * - encoding: unused
+     */
+    char *sub_charenc;
+
+    /**
+     * Subtitles character encoding mode. Formats or codecs might be adjusting
+     * this setting (if they are doing the conversion themselves for instance).
+     * - decoding: set by libavcodec
+     * - encoding: unused
+     */
+    int sub_charenc_mode;
+#define FF_SUB_CHARENC_MODE_DO_NOTHING  -1  ///< do nothing (demuxer outputs a stream supposed to be already in UTF-8, or the codec is bitmap for instance)
+#define FF_SUB_CHARENC_MODE_AUTOMATIC    0  ///< libavcodec will select the mode itself
+#define FF_SUB_CHARENC_MODE_PRE_DECODER  1  ///< the AVPacket data needs to be recoded to UTF-8 before being fed to the decoder, requires iconv
+#define FF_SUB_CHARENC_MODE_IGNORE       2  ///< neither convert the subtitles, nor check them for valid UTF-8
+
+    /**
+     * Skip processing alpha if supported by codec.
+     * Note that if the format uses pre-multiplied alpha (common with VP6,
+     * and recommended due to better video quality/compression)
+     * the image will look as if alpha-blended onto a black background.
+     * However for formats that do not use pre-multiplied alpha
+     * there might be serious artefacts (though e.g. libswscale currently
+     * assumes pre-multiplied alpha anyway).
+     *
+     * - decoding: set by user
+     * - encoding: unused
+     */
+    int skip_alpha;
+
+    /**
+     * Number of samples to skip after a discontinuity
+     * - decoding: unused
+     * - encoding: set by libavcodec
+     */
+    int seek_preroll;
+
+    /**
+     * custom intra quantization matrix
+     * - encoding: Set by user, can be NULL.
+     * - decoding: unused.
+     */
+    uint16_t *chroma_intra_matrix;
+
+    /**
+     * dump format separator.
+     * can be ", " or "\n      " or anything else
+     * - encoding: Set by user.
+     * - decoding: Set by user.
+     */
+    uint8_t *dump_separator;
+
+    /**
+     * ',' separated list of allowed decoders.
+     * If NULL then all are allowed
+     * - encoding: unused
+     * - decoding: set by user
+     */
+    char *codec_whitelist;
+
+    /**
+     * Properties of the stream that gets decoded
+     * - encoding: unused
+     * - decoding: set by libavcodec
+     */
+    unsigned properties;
+#define FF_CODEC_PROPERTY_LOSSLESS        0x00000001
+#define FF_CODEC_PROPERTY_CLOSED_CAPTIONS 0x00000002
+#define FF_CODEC_PROPERTY_FILM_GRAIN      0x00000004
+
+    /**
+     * Additional data associated with the entire coded stream.
+     *
+     * - decoding: unused
+     * - encoding: may be set by libavcodec after avcodec_open2().
+     */
+    AVPacketSideData *coded_side_data;
+    int            nb_coded_side_data;
+
+    /**
+     * A reference to the AVHWFramesContext describing the input (for encoding)
+     * or output (decoding) frames. The reference is set by the caller and
+     * afterwards owned (and freed) by libavcodec - it should never be read by
+     * the caller after being set.
+     *
+     * - decoding: This field should be set by the caller from the get_format()
+     *             callback. The previous reference (if any) will always be
+     *             unreffed by libavcodec before the get_format() call.
+     *
+     *             If the default get_buffer2() is used with a hwaccel pixel
+     *             format, then this AVHWFramesContext will be used for
+     *             allocating the frame buffers.
+     *
+     * - encoding: For hardware encoders configured to use a hwaccel pixel
+     *             format, this field should be set by the caller to a reference
+     *             to the AVHWFramesContext describing input frames.
+     *             AVHWFramesContext.format must be equal to
+     *             AVCodecContext.pix_fmt.
+     *
+     *             This field should be set before avcodec_open2() is called.
+     */
+    AVBufferRef *hw_frames_ctx;
+
+    /**
+     * Audio only. The amount of padding (in samples) appended by the encoder to
+     * the end of the audio. I.e. this number of decoded samples must be
+     * discarded by the caller from the end of the stream to get the original
+     * audio without any trailing padding.
+     *
+     * - decoding: unused
+     * - encoding: unused
+     */
+    int trailing_padding;
+
+    /**
+     * The number of pixels per image to maximally accept.
+     *
+     * - decoding: set by user
+     * - encoding: set by user
+     */
+    int64_t max_pixels;
+
+    /**
+     * A reference to the AVHWDeviceContext describing the device which will
+     * be used by a hardware encoder/decoder.  The reference is set by the
+     * caller and afterwards owned (and freed) by libavcodec.
+     *
+     * This should be used if either the codec device does not require
+     * hardware frames or any that are used are to be allocated internally by
+     * libavcodec.  If the user wishes to supply any of the frames used as
+     * encoder input or decoder output then hw_frames_ctx should be used
+     * instead.  When hw_frames_ctx is set in get_format() for a decoder, this
+     * field will be ignored while decoding the associated stream segment, but
+     * may again be used on a following one after another get_format() call.
+     *
+     * For both encoders and decoders this field should be set before
+     * avcodec_open2() is called and must not be written to thereafter.
+     *
+     * Note that some decoders may require this field to be set initially in
+     * order to support hw_frames_ctx at all - in that case, all frames
+     * contexts used must be created on the same device.
+     */
+    AVBufferRef *hw_device_ctx;
+
+    /**
+     * Bit set of AV_HWACCEL_FLAG_* flags, which affect hardware accelerated
+     * decoding (if active).
+     * - encoding: unused
+     * - decoding: Set by user (either before avcodec_open2(), or in the
+     *             AVCodecContext.get_format callback)
+     */
+    int hwaccel_flags;
+
+    /**
+     * Video decoding only. Certain video codecs support cropping, meaning that
+     * only a sub-rectangle of the decoded frame is intended for display.  This
+     * option controls how cropping is handled by libavcodec.
+     *
+     * When set to 1 (the default), libavcodec will apply cropping internally.
+     * I.e. it will modify the output frame width/height fields and offset the
+     * data pointers (only by as much as possible while preserving alignment, or
+     * by the full amount if the AV_CODEC_FLAG_UNALIGNED flag is set) so that
+     * the frames output by the decoder refer only to the cropped area. The
+     * crop_* fields of the output frames will be zero.
+     *
+     * When set to 0, the width/height fields of the output frames will be set
+     * to the coded dimensions and the crop_* fields will describe the cropping
+     * rectangle. Applying the cropping is left to the caller.
+     *
+     * @warning When hardware acceleration with opaque output frames is used,
+     * libavcodec is unable to apply cropping from the top/left border.
+     *
+     * @note when this option is set to zero, the width/height fields of the
+     * AVCodecContext and output AVFrames have different meanings. The codec
+     * context fields store display dimensions (with the coded dimensions in
+     * coded_width/height), while the frame fields store the coded dimensions
+     * (with the display dimensions being determined by the crop_* fields).
+     */
+    int apply_cropping;
+
+    /*
+     * Video decoding only.  Sets the number of extra hardware frames which
+     * the decoder will allocate for use by the caller.  This must be set
+     * before avcodec_open2() is called.
+     *
+     * Some hardware decoders require all frames that they will use for
+     * output to be defined in advance before decoding starts.  For such
+     * decoders, the hardware frame pool must therefore be of a fixed size.
+     * The extra frames set here are on top of any number that the decoder
+     * needs internally in order to operate normally (for example, frames
+     * used as reference pictures).
+     */
+    int extra_hw_frames;
+
+    /**
+     * The percentage of damaged samples to discard a frame.
+     *
+     * - decoding: set by user
+     * - encoding: unused
+     */
+    int discard_damaged_percentage;
+
+    /**
+     * The number of samples per frame to maximally accept.
+     *
+     * - decoding: set by user
+     * - encoding: set by user
+     */
+    int64_t max_samples;
+
+    /**
+     * Bit set of AV_CODEC_EXPORT_DATA_* flags, which affects the kind of
+     * metadata exported in frame, packet, or coded stream side data by
+     * decoders and encoders.
+     *
+     * - decoding: set by user
+     * - encoding: set by user
+     */
+    int export_side_data;
+
+    /**
+     * This callback is called at the beginning of each packet to get a data
+     * buffer for it.
+     *
+     * The following field will be set in the packet before this callback is
+     * called:
+     * - size
+     * This callback must use the above value to calculate the required buffer size,
+     * which must padded by at least AV_INPUT_BUFFER_PADDING_SIZE bytes.
+     *
+     * In some specific cases, the encoder may not use the entire buffer allocated by this
+     * callback. This will be reflected in the size value in the packet once returned by
+     * avcodec_receive_packet().
+     *
+     * This callback must fill the following fields in the packet:
+     * - data: alignment requirements for AVPacket apply, if any. Some architectures and
+     *   encoders may benefit from having aligned data.
+     * - buf: must contain a pointer to an AVBufferRef structure. The packet's
+     *   data pointer must be contained in it. See: av_buffer_create(), av_buffer_alloc(),
+     *   and av_buffer_ref().
+     *
+     * If AV_CODEC_CAP_DR1 is not set then get_encode_buffer() must call
+     * avcodec_default_get_encode_buffer() instead of providing a buffer allocated by
+     * some other means.
+     *
+     * The flags field may contain a combination of AV_GET_ENCODE_BUFFER_FLAG_ flags.
+     * They may be used for example to hint what use the buffer may get after being
+     * created.
+     * Implementations of this callback may ignore flags they don't understand.
+     * If AV_GET_ENCODE_BUFFER_FLAG_REF is set in flags then the packet may be reused
+     * (read and/or written to if it is writable) later by libavcodec.
+     *
+     * This callback must be thread-safe, as when frame threading is used, it may
+     * be called from multiple threads simultaneously.
+     *
+     * @see avcodec_default_get_encode_buffer()
+     *
+     * - encoding: Set by libavcodec, user can override.
+     * - decoding: unused
+     */
+    int (*get_encode_buffer)(struct AVCodecContext *s, AVPacket *pkt, int flags);
+
+    /**
+     * Audio channel layout.
+     * - encoding: must be set by the caller, to one of AVCodec.ch_layouts.
+     * - decoding: may be set by the caller if known e.g. from the container.
+     *             The decoder can then override during decoding as needed.
+     */
+    AVChannelLayout ch_layout;
+
+    /**
+     * Frame counter, set by libavcodec.
+     *
+     * - decoding: total number of frames returned from the decoder so far.
+     * - encoding: total number of frames passed to the encoder so far.
+     *
+     *   @note the counter is not incremented if encoding/decoding resulted in
+     *   an error.
+     */
+    int64_t frame_num;
+} AVCodecContext;
+
+/**
+ * @defgroup lavc_hwaccel AVHWAccel
+ *
+ * @note  Nothing in this structure should be accessed by the user.  At some
+ *        point in future it will not be externally visible at all.
+ *
+ * @{
+ */
+typedef struct AVHWAccel {
+    /**
+     * Name of the hardware accelerated codec.
+     * The name is globally unique among encoders and among decoders (but an
+     * encoder and a decoder can share the same name).
+     */
+    const char *name;
+
+    /**
+     * Type of codec implemented by the hardware accelerator.
+     *
+     * See AVMEDIA_TYPE_xxx
+     */
+    enum AVMediaType type;
+
+    /**
+     * Codec implemented by the hardware accelerator.
+     *
+     * See AV_CODEC_ID_xxx
+     */
+    enum AVCodecID id;
+
+    /**
+     * Supported pixel format.
+     *
+     * Only hardware accelerated formats are supported here.
+     */
+    enum AVPixelFormat pix_fmt;
+
+    /**
+     * Hardware accelerated codec capabilities.
+     * see AV_HWACCEL_CODEC_CAP_*
+     */
+    int capabilities;
+
+    /*****************************************************************
+     * No fields below this line are part of the public API. They
+     * may not be used outside of libavcodec and can be changed and
+     * removed at will.
+     * New public fields should be added right above.
+     *****************************************************************
+     */
+
+    /**
+     * Allocate a custom buffer
+     */
+    int (*alloc_frame)(AVCodecContext *avctx, AVFrame *frame);
+
+    /**
+     * Called at the beginning of each frame or field picture.
+     *
+     * Meaningful frame information (codec specific) is guaranteed to
+     * be parsed at this point. This function is mandatory.
+     *
+     * Note that buf can be NULL along with buf_size set to 0.
+     * Otherwise, this means the whole frame is available at this point.
+     *
+     * @param avctx the codec context
+     * @param buf the frame data buffer base
+     * @param buf_size the size of the frame in bytes
+     * @return zero if successful, a negative value otherwise
+     */
+    int (*start_frame)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);
+
+    /**
+     * Callback for parameter data (SPS/PPS/VPS etc).
+     *
+     * Useful for hardware decoders which keep persistent state about the
+     * video parameters, and need to receive any changes to update that state.
+     *
+     * @param avctx the codec context
+     * @param type the nal unit type
+     * @param buf the nal unit data buffer
+     * @param buf_size the size of the nal unit in bytes
+     * @return zero if successful, a negative value otherwise
+     */
+    int (*decode_params)(AVCodecContext *avctx, int type, const uint8_t *buf, uint32_t buf_size);
+
+    /**
+     * Callback for each slice.
+     *
+     * Meaningful slice information (codec specific) is guaranteed to
+     * be parsed at this point. This function is mandatory.
+     *
+     * @param avctx the codec context
+     * @param buf the slice data buffer base
+     * @param buf_size the size of the slice in bytes
+     * @return zero if successful, a negative value otherwise
+     */
+    int (*decode_slice)(AVCodecContext *avctx, const uint8_t *buf, uint32_t buf_size);
+
+    /**
+     * Called at the end of each frame or field picture.
+     *
+     * The whole picture is parsed at this point and can now be sent
+     * to the hardware accelerator. This function is mandatory.
+     *
+     * @param avctx the codec context
+     * @return zero if successful, a negative value otherwise
+     */
+    int (*end_frame)(AVCodecContext *avctx);
+
+    /**
+     * Size of per-frame hardware accelerator private data.
+     *
+     * Private data is allocated with av_mallocz() before
+     * AVCodecContext.get_buffer() and deallocated after
+     * AVCodecContext.release_buffer().
+     */
+    int frame_priv_data_size;
+
+    /**
+     * Initialize the hwaccel private data.
+     *
+     * This will be called from ff_get_format(), after hwaccel and
+     * hwaccel_context are set and the hwaccel private data in AVCodecInternal
+     * is allocated.
+     */
+    int (*init)(AVCodecContext *avctx);
+
+    /**
+     * Uninitialize the hwaccel private data.
+     *
+     * This will be called from get_format() or avcodec_close(), after hwaccel
+     * and hwaccel_context are already uninitialized.
+     */
+    int (*uninit)(AVCodecContext *avctx);
+
+    /**
+     * Size of the private data to allocate in
+     * AVCodecInternal.hwaccel_priv_data.
+     */
+    int priv_data_size;
+
+    /**
+     * Internal hwaccel capabilities.
+     */
+    int caps_internal;
+
+    /**
+     * Fill the given hw_frames context with current codec parameters. Called
+     * from get_format. Refer to avcodec_get_hw_frames_parameters() for
+     * details.
+     *
+     * This CAN be called before AVHWAccel.init is called, and you must assume
+     * that avctx->hwaccel_priv_data is invalid.
+     */
+    int (*frame_params)(AVCodecContext *avctx, AVBufferRef *hw_frames_ctx);
+} AVHWAccel;
+
+/**
+ * HWAccel is experimental and is thus avoided in favor of non experimental
+ * codecs
+ */
+#define AV_HWACCEL_CODEC_CAP_EXPERIMENTAL 0x0200
+
+/**
+ * Hardware acceleration should be used for decoding even if the codec level
+ * used is unknown or higher than the maximum supported level reported by the
+ * hardware driver.
+ *
+ * It's generally a good idea to pass this flag unless you have a specific
+ * reason not to, as hardware tends to under-report supported levels.
+ */
+#define AV_HWACCEL_FLAG_IGNORE_LEVEL (1 << 0)
+
+/**
+ * Hardware acceleration can output YUV pixel formats with a different chroma
+ * sampling than 4:2:0 and/or other than 8 bits per component.
+ */
+#define AV_HWACCEL_FLAG_ALLOW_HIGH_DEPTH (1 << 1)
+
+/**
+ * Hardware acceleration should still be attempted for decoding when the
+ * codec profile does not match the reported capabilities of the hardware.
+ *
+ * For example, this can be used to try to decode baseline profile H.264
+ * streams in hardware - it will often succeed, because many streams marked
+ * as baseline profile actually conform to constrained baseline profile.
+ *
+ * @warning If the stream is actually not supported then the behaviour is
+ *          undefined, and may include returning entirely incorrect output
+ *          while indicating success.
+ */
+#define AV_HWACCEL_FLAG_ALLOW_PROFILE_MISMATCH (1 << 2)
+
+/**
+ * Some hardware decoders (namely nvdec) can either output direct decoder
+ * surfaces, or make an on-device copy and return said copy.
+ * There is a hard limit on how many decoder surfaces there can be, and it
+ * cannot be accurately guessed ahead of time.
+ * For some processing chains, this can be okay, but others will run into the
+ * limit and in turn produce very confusing errors that require fine tuning of
+ * more or less obscure options by the user, or in extreme cases cannot be
+ * resolved at all without inserting an avfilter that forces a copy.
+ *
+ * Thus, the hwaccel will by default make a copy for safety and resilience.
+ * If a users really wants to minimize the amount of copies, they can set this
+ * flag and ensure their processing chain does not exhaust the surface pool.
+ */
+#define AV_HWACCEL_FLAG_UNSAFE_OUTPUT (1 << 3)
+
+/**
+ * @}
+ */
+
+enum AVSubtitleType {
+    SUBTITLE_NONE,
+
+    SUBTITLE_BITMAP,                ///< A bitmap, pict will be set
+
+    /**
+     * Plain text, the text field must be set by the decoder and is
+     * authoritative. ass and pict fields may contain approximations.
+     */
+    SUBTITLE_TEXT,
+
+    /**
+     * Formatted text, the ass field must be set by the decoder and is
+     * authoritative. pict and text fields may contain approximations.
+     */
+    SUBTITLE_ASS,
+};
+
+#define AV_SUBTITLE_FLAG_FORCED 0x00000001
+
+typedef struct AVSubtitleRect {
+    int x;         ///< top left corner  of pict, undefined when pict is not set
+    int y;         ///< top left corner  of pict, undefined when pict is not set
+    int w;         ///< width            of pict, undefined when pict is not set
+    int h;         ///< height           of pict, undefined when pict is not set
+    int nb_colors; ///< number of colors in pict, undefined when pict is not set
+
+    /**
+     * data+linesize for the bitmap of this subtitle.
+     * Can be set for text/ass as well once they are rendered.
+     */
+    uint8_t *data[4];
+    int linesize[4];
+
+    enum AVSubtitleType type;
+
+    char *text;                     ///< 0 terminated plain UTF-8 text
+
+    /**
+     * 0 terminated ASS/SSA compatible event line.
+     * The presentation of this is unaffected by the other values in this
+     * struct.
+     */
+    char *ass;
+
+    int flags;
+} AVSubtitleRect;
+
+typedef struct AVSubtitle {
+    uint16_t format; /* 0 = graphics */
+    uint32_t start_display_time; /* relative to packet pts, in ms */
+    uint32_t end_display_time; /* relative to packet pts, in ms */
+    unsigned num_rects;
+    AVSubtitleRect **rects;
+    int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
+} AVSubtitle;
+
+/**
+ * Return the LIBAVCODEC_VERSION_INT constant.
+ */
+unsigned avcodec_version(void);
+
+/**
+ * Return the libavcodec build-time configuration.
+ */
+const char *avcodec_configuration(void);
+
+/**
+ * Return the libavcodec license.
+ */
+const char *avcodec_license(void);
+
+/**
+ * Allocate an AVCodecContext and set its fields to default values. The
+ * resulting struct should be freed with avcodec_free_context().
+ *
+ * @param codec if non-NULL, allocate private data and initialize defaults
+ *              for the given codec. It is illegal to then call avcodec_open2()
+ *              with a different codec.
+ *              If NULL, then the codec-specific defaults won't be initialized,
+ *              which may result in suboptimal default settings (this is
+ *              important mainly for encoders, e.g. libx264).
+ *
+ * @return An AVCodecContext filled with default values or NULL on failure.
+ */
+AVCodecContext *avcodec_alloc_context3(const AVCodec *codec);
+
+/**
+ * Free the codec context and everything associated with it and write NULL to
+ * the provided pointer.
+ */
+void avcodec_free_context(AVCodecContext **avctx);
+
+/**
+ * Get the AVClass for AVCodecContext. It can be used in combination with
+ * AV_OPT_SEARCH_FAKE_OBJ for examining options.
+ *
+ * @see av_opt_find().
+ */
+const AVClass *avcodec_get_class(void);
+
+/**
+ * Get the AVClass for AVSubtitleRect. It can be used in combination with
+ * AV_OPT_SEARCH_FAKE_OBJ for examining options.
+ *
+ * @see av_opt_find().
+ */
+const AVClass *avcodec_get_subtitle_rect_class(void);
+
+/**
+ * Fill the parameters struct based on the values from the supplied codec
+ * context. Any allocated fields in par are freed and replaced with duplicates
+ * of the corresponding fields in codec.
+ *
+ * @return >= 0 on success, a negative AVERROR code on failure
+ */
+int avcodec_parameters_from_context(AVCodecParameters *par,
+                                    const AVCodecContext *codec);
+
+/**
+ * Fill the codec context based on the values from the supplied codec
+ * parameters. Any allocated fields in codec that have a corresponding field in
+ * par are freed and replaced with duplicates of the corresponding field in par.
+ * Fields in codec that do not have a counterpart in par are not touched.
+ *
+ * @return >= 0 on success, a negative AVERROR code on failure.
+ */
+int avcodec_parameters_to_context(AVCodecContext *codec,
+                                  const AVCodecParameters *par);
+
+/**
+ * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
+ * function the context has to be allocated with avcodec_alloc_context3().
+ *
+ * The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
+ * avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
+ * retrieving a codec.
+ *
+ * @note Always call this function before using decoding routines (such as
+ * @ref avcodec_receive_frame()).
+ *
+ * @code
+ * av_dict_set(&opts, "b", "2.5M", 0);
+ * codec = avcodec_find_decoder(AV_CODEC_ID_H264);
+ * if (!codec)
+ *     exit(1);
+ *
+ * context = avcodec_alloc_context3(codec);
+ *
+ * if (avcodec_open2(context, codec, opts) < 0)
+ *     exit(1);
+ * @endcode
+ *
+ * @param avctx The context to initialize.
+ * @param codec The codec to open this context for. If a non-NULL codec has been
+ *              previously passed to avcodec_alloc_context3() or
+ *              for this context, then this parameter MUST be either NULL or
+ *              equal to the previously passed codec.
+ * @param options A dictionary filled with AVCodecContext and codec-private options.
+ *                On return this object will be filled with options that were not found.
+ *
+ * @return zero on success, a negative value on error
+ * @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(),
+ *      av_dict_set(), av_opt_find().
+ */
+int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options);
+
+/**
+ * Close a given AVCodecContext and free all the data associated with it
+ * (but not the AVCodecContext itself).
+ *
+ * Calling this function on an AVCodecContext that hasn't been opened will free
+ * the codec-specific data allocated in avcodec_alloc_context3() with a non-NULL
+ * codec. Subsequent calls will do nothing.
+ *
+ * @note Do not use this function. Use avcodec_free_context() to destroy a
+ * codec context (either open or closed). Opening and closing a codec context
+ * multiple times is not supported anymore -- use multiple codec contexts
+ * instead.
+ */
+int avcodec_close(AVCodecContext *avctx);
+
+/**
+ * Free all allocated data in the given subtitle struct.
+ *
+ * @param sub AVSubtitle to free.
+ */
+void avsubtitle_free(AVSubtitle *sub);
+
+/**
+ * @}
+ */
+
+/**
+ * @addtogroup lavc_decoding
+ * @{
+ */
+
+/**
+ * The default callback for AVCodecContext.get_buffer2(). It is made public so
+ * it can be called by custom get_buffer2() implementations for decoders without
+ * AV_CODEC_CAP_DR1 set.
+ */
+int avcodec_default_get_buffer2(AVCodecContext *s, AVFrame *frame, int flags);
+
+/**
+ * The default callback for AVCodecContext.get_encode_buffer(). It is made public so
+ * it can be called by custom get_encode_buffer() implementations for encoders without
+ * AV_CODEC_CAP_DR1 set.
+ */
+int avcodec_default_get_encode_buffer(AVCodecContext *s, AVPacket *pkt, int flags);
+
+/**
+ * Modify width and height values so that they will result in a memory
+ * buffer that is acceptable for the codec if you do not use any horizontal
+ * padding.
+ *
+ * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
+ */
+void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height);
+
+/**
+ * Modify width and height values so that they will result in a memory
+ * buffer that is acceptable for the codec if you also ensure that all
+ * line sizes are a multiple of the respective linesize_align[i].
+ *
+ * May only be used if a codec with AV_CODEC_CAP_DR1 has been opened.
+ */
+void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
+                               int linesize_align[AV_NUM_DATA_POINTERS]);
+
+#ifdef FF_API_AVCODEC_CHROMA_POS
+/**
+ * Converts AVChromaLocation to swscale x/y chroma position.
+ *
+ * The positions represent the chroma (0,0) position in a coordinates system
+ * with luma (0,0) representing the origin and luma(1,1) representing 256,256
+ *
+ * @param xpos  horizontal chroma sample position
+ * @param ypos  vertical   chroma sample position
+ * @deprecated Use av_chroma_location_enum_to_pos() instead.
+ */
+ attribute_deprecated
+int avcodec_enum_to_chroma_pos(int *xpos, int *ypos, enum AVChromaLocation pos);
+
+/**
+ * Converts swscale x/y chroma position to AVChromaLocation.
+ *
+ * The positions represent the chroma (0,0) position in a coordinates system
+ * with luma (0,0) representing the origin and luma(1,1) representing 256,256
+ *
+ * @param xpos  horizontal chroma sample position
+ * @param ypos  vertical   chroma sample position
+ * @deprecated Use av_chroma_location_pos_to_enum() instead.
+ */
+ attribute_deprecated
+enum AVChromaLocation avcodec_chroma_pos_to_enum(int xpos, int ypos);
+#endif
+
+/**
+ * Decode a subtitle message.
+ * Return a negative value on error, otherwise return the number of bytes used.
+ * If no subtitle could be decompressed, got_sub_ptr is zero.
+ * Otherwise, the subtitle is stored in *sub.
+ * Note that AV_CODEC_CAP_DR1 is not available for subtitle codecs. This is for
+ * simplicity, because the performance difference is expected to be negligible
+ * and reusing a get_buffer written for video codecs would probably perform badly
+ * due to a potentially very different allocation pattern.
+ *
+ * Some decoders (those marked with AV_CODEC_CAP_DELAY) have a delay between input
+ * and output. This means that for some packets they will not immediately
+ * produce decoded output and need to be flushed at the end of decoding to get
+ * all the decoded data. Flushing is done by calling this function with packets
+ * with avpkt->data set to NULL and avpkt->size set to 0 until it stops
+ * returning subtitles. It is safe to flush even those decoders that are not
+ * marked with AV_CODEC_CAP_DELAY, then no subtitles will be returned.
+ *
+ * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
+ * before packets may be fed to the decoder.
+ *
+ * @param avctx the codec context
+ * @param[out] sub The preallocated AVSubtitle in which the decoded subtitle will be stored,
+ *                 must be freed with avsubtitle_free if *got_sub_ptr is set.
+ * @param[in,out] got_sub_ptr Zero if no subtitle could be decompressed, otherwise, it is nonzero.
+ * @param[in] avpkt The input AVPacket containing the input buffer.
+ */
+int avcodec_decode_subtitle2(AVCodecContext *avctx, AVSubtitle *sub,
+                             int *got_sub_ptr, const AVPacket *avpkt);
+
+/**
+ * Supply raw packet data as input to a decoder.
+ *
+ * Internally, this call will copy relevant AVCodecContext fields, which can
+ * influence decoding per-packet, and apply them when the packet is actually
+ * decoded. (For example AVCodecContext.skip_frame, which might direct the
+ * decoder to drop the frame contained by the packet sent with this function.)
+ *
+ * @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
+ *          larger than the actual read bytes because some optimized bitstream
+ *          readers read 32 or 64 bits at once and could read over the end.
+ *
+ * @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
+ *       before packets may be fed to the decoder.
+ *
+ * @param avctx codec context
+ * @param[in] avpkt The input AVPacket. Usually, this will be a single video
+ *                  frame, or several complete audio frames.
+ *                  Ownership of the packet remains with the caller, and the
+ *                  decoder will not write to the packet. The decoder may create
+ *                  a reference to the packet data (or copy it if the packet is
+ *                  not reference-counted).
+ *                  Unlike with older APIs, the packet is always fully consumed,
+ *                  and if it contains multiple frames (e.g. some audio codecs),
+ *                  will require you to call avcodec_receive_frame() multiple
+ *                  times afterwards before you can send a new packet.
+ *                  It can be NULL (or an AVPacket with data set to NULL and
+ *                  size set to 0); in this case, it is considered a flush
+ *                  packet, which signals the end of the stream. Sending the
+ *                  first flush packet will return success. Subsequent ones are
+ *                  unnecessary and will return AVERROR_EOF. If the decoder
+ *                  still has frames buffered, it will return them after sending
+ *                  a flush packet.
+ *
+ * @retval 0                 success
+ * @retval AVERROR(EAGAIN)   input is not accepted in the current state - user
+ *                           must read output with avcodec_receive_frame() (once
+ *                           all output is read, the packet should be resent,
+ *                           and the call will not fail with EAGAIN).
+ * @retval AVERROR_EOF       the decoder has been flushed, and no new packets can be
+ *                           sent to it (also returned if more than 1 flush
+ *                           packet is sent)
+ * @retval AVERROR(EINVAL)   codec not opened, it is an encoder, or requires flush
+ * @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
+ * @retval "another negative error code" legitimate decoding errors
+ */
+int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt);
+
+/**
+ * Return decoded output data from a decoder or encoder (when the
+ * AV_CODEC_FLAG_RECON_FRAME flag is used).
+ *
+ * @param avctx codec context
+ * @param frame This will be set to a reference-counted video or audio
+ *              frame (depending on the decoder type) allocated by the
+ *              codec. Note that the function will always call
+ *              av_frame_unref(frame) before doing anything else.
+ *
+ * @retval 0                success, a frame was returned
+ * @retval AVERROR(EAGAIN)  output is not available in this state - user must
+ *                          try to send new input
+ * @retval AVERROR_EOF      the codec has been fully flushed, and there will be
+ *                          no more output frames
+ * @retval AVERROR(EINVAL)  codec not opened, or it is an encoder without the
+ *                          AV_CODEC_FLAG_RECON_FRAME flag enabled
+ * @retval AVERROR_INPUT_CHANGED current decoded frame has changed parameters with
+ *                          respect to first decoded frame. Applicable when flag
+ *                          AV_CODEC_FLAG_DROPCHANGED is set.
+ * @retval "other negative error code" legitimate decoding errors
+ */
+int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame);
+
+/**
+ * Supply a raw video or audio frame to the encoder. Use avcodec_receive_packet()
+ * to retrieve buffered output packets.
+ *
+ * @param avctx     codec context
+ * @param[in] frame AVFrame containing the raw audio or video frame to be encoded.
+ *                  Ownership of the frame remains with the caller, and the
+ *                  encoder will not write to the frame. The encoder may create
+ *                  a reference to the frame data (or copy it if the frame is
+ *                  not reference-counted).
+ *                  It can be NULL, in which case it is considered a flush
+ *                  packet.  This signals the end of the stream. If the encoder
+ *                  still has packets buffered, it will return them after this
+ *                  call. Once flushing mode has been entered, additional flush
+ *                  packets are ignored, and sending frames will return
+ *                  AVERROR_EOF.
+ *
+ *                  For audio:
+ *                  If AV_CODEC_CAP_VARIABLE_FRAME_SIZE is set, then each frame
+ *                  can have any number of samples.
+ *                  If it is not set, frame->nb_samples must be equal to
+ *                  avctx->frame_size for all frames except the last.
+ *                  The final frame may be smaller than avctx->frame_size.
+ * @retval 0                 success
+ * @retval AVERROR(EAGAIN)   input is not accepted in the current state - user must
+ *                           read output with avcodec_receive_packet() (once all
+ *                           output is read, the packet should be resent, and the
+ *                           call will not fail with EAGAIN).
+ * @retval AVERROR_EOF       the encoder has been flushed, and no new frames can
+ *                           be sent to it
+ * @retval AVERROR(EINVAL)   codec not opened, it is a decoder, or requires flush
+ * @retval AVERROR(ENOMEM)   failed to add packet to internal queue, or similar
+ * @retval "another negative error code" legitimate encoding errors
+ */
+int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);
+
+/**
+ * Read encoded data from the encoder.
+ *
+ * @param avctx codec context
+ * @param avpkt This will be set to a reference-counted packet allocated by the
+ *              encoder. Note that the function will always call
+ *              av_packet_unref(avpkt) before doing anything else.
+ * @retval 0               success
+ * @retval AVERROR(EAGAIN) output is not available in the current state - user must
+ *                         try to send input
+ * @retval AVERROR_EOF     the encoder has been fully flushed, and there will be no
+ *                         more output packets
+ * @retval AVERROR(EINVAL) codec not opened, or it is a decoder
+ * @retval "another negative error code" legitimate encoding errors
+ */
+int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);
+
+/**
+ * Create and return a AVHWFramesContext with values adequate for hardware
+ * decoding. This is meant to get called from the get_format callback, and is
+ * a helper for preparing a AVHWFramesContext for AVCodecContext.hw_frames_ctx.
+ * This API is for decoding with certain hardware acceleration modes/APIs only.
+ *
+ * The returned AVHWFramesContext is not initialized. The caller must do this
+ * with av_hwframe_ctx_init().
+ *
+ * Calling this function is not a requirement, but makes it simpler to avoid
+ * codec or hardware API specific details when manually allocating frames.
+ *
+ * Alternatively to this, an API user can set AVCodecContext.hw_device_ctx,
+ * which sets up AVCodecContext.hw_frames_ctx fully automatically, and makes
+ * it unnecessary to call this function or having to care about
+ * AVHWFramesContext initialization at all.
+ *
+ * There are a number of requirements for calling this function:
+ *
+ * - It must be called from get_format with the same avctx parameter that was
+ *   passed to get_format. Calling it outside of get_format is not allowed, and
+ *   can trigger undefined behavior.
+ * - The function is not always supported (see description of return values).
+ *   Even if this function returns successfully, hwaccel initialization could
+ *   fail later. (The degree to which implementations check whether the stream
+ *   is actually supported varies. Some do this check only after the user's
+ *   get_format callback returns.)
+ * - The hw_pix_fmt must be one of the choices suggested by get_format. If the
+ *   user decides to use a AVHWFramesContext prepared with this API function,
+ *   the user must return the same hw_pix_fmt from get_format.
+ * - The device_ref passed to this function must support the given hw_pix_fmt.
+ * - After calling this API function, it is the user's responsibility to
+ *   initialize the AVHWFramesContext (returned by the out_frames_ref parameter),
+ *   and to set AVCodecContext.hw_frames_ctx to it. If done, this must be done
+ *   before returning from get_format (this is implied by the normal
+ *   AVCodecContext.hw_frames_ctx API rules).
+ * - The AVHWFramesContext parameters may change every time time get_format is
+ *   called. Also, AVCodecContext.hw_frames_ctx is reset before get_format. So
+ *   you are inherently required to go through this process again on every
+ *   get_format call.
+ * - It is perfectly possible to call this function without actually using
+ *   the resulting AVHWFramesContext. One use-case might be trying to reuse a
+ *   previously initialized AVHWFramesContext, and calling this API function
+ *   only to test whether the required frame parameters have changed.
+ * - Fields that use dynamically allocated values of any kind must not be set
+ *   by the user unless setting them is explicitly allowed by the documentation.
+ *   If the user sets AVHWFramesContext.free and AVHWFramesContext.user_opaque,
+ *   the new free callback must call the potentially set previous free callback.
+ *   This API call may set any dynamically allocated fields, including the free
+ *   callback.
+ *
+ * The function will set at least the following fields on AVHWFramesContext
+ * (potentially more, depending on hwaccel API):
+ *
+ * - All fields set by av_hwframe_ctx_alloc().
+ * - Set the format field to hw_pix_fmt.
+ * - Set the sw_format field to the most suited and most versatile format. (An
+ *   implication is that this will prefer generic formats over opaque formats
+ *   with arbitrary restrictions, if possible.)
+ * - Set the width/height fields to the coded frame size, rounded up to the
+ *   API-specific minimum alignment.
+ * - Only _if_ the hwaccel requires a pre-allocated pool: set the initial_pool_size
+ *   field to the number of maximum reference surfaces possible with the codec,
+ *   plus 1 surface for the user to work (meaning the user can safely reference
+ *   at most 1 decoded surface at a time), plus additional buffering introduced
+ *   by frame threading. If the hwaccel does not require pre-allocation, the
+ *   field is left to 0, and the decoder will allocate new surfaces on demand
+ *   during decoding.
+ * - Possibly AVHWFramesContext.hwctx fields, depending on the underlying
+ *   hardware API.
+ *
+ * Essentially, out_frames_ref returns the same as av_hwframe_ctx_alloc(), but
+ * with basic frame parameters set.
+ *
+ * The function is stateless, and does not change the AVCodecContext or the
+ * device_ref AVHWDeviceContext.
+ *
+ * @param avctx The context which is currently calling get_format, and which
+ *              implicitly contains all state needed for filling the returned
+ *              AVHWFramesContext properly.
+ * @param device_ref A reference to the AVHWDeviceContext describing the device
+ *                   which will be used by the hardware decoder.
+ * @param hw_pix_fmt The hwaccel format you are going to return from get_format.
+ * @param out_frames_ref On success, set to a reference to an _uninitialized_
+ *                       AVHWFramesContext, created from the given device_ref.
+ *                       Fields will be set to values required for decoding.
+ *                       Not changed if an error is returned.
+ * @return zero on success, a negative value on error. The following error codes
+ *         have special semantics:
+ *      AVERROR(ENOENT): the decoder does not support this functionality. Setup
+ *                       is always manual, or it is a decoder which does not
+ *                       support setting AVCodecContext.hw_frames_ctx at all,
+ *                       or it is a software format.
+ *      AVERROR(EINVAL): it is known that hardware decoding is not supported for
+ *                       this configuration, or the device_ref is not supported
+ *                       for the hwaccel referenced by hw_pix_fmt.
+ */
+int avcodec_get_hw_frames_parameters(AVCodecContext *avctx,
+                                     AVBufferRef *device_ref,
+                                     enum AVPixelFormat hw_pix_fmt,
+                                     AVBufferRef **out_frames_ref);
+
+
+
+/**
+ * @defgroup lavc_parsing Frame parsing
+ * @{
+ */
+
+enum AVPictureStructure {
+    AV_PICTURE_STRUCTURE_UNKNOWN,      ///< unknown
+    AV_PICTURE_STRUCTURE_TOP_FIELD,    ///< coded as top field
+    AV_PICTURE_STRUCTURE_BOTTOM_FIELD, ///< coded as bottom field
+    AV_PICTURE_STRUCTURE_FRAME,        ///< coded as frame
+};
+
+typedef struct AVCodecParserContext {
+    void *priv_data;
+    const struct AVCodecParser *parser;
+    int64_t frame_offset; /* offset of the current frame */
+    int64_t cur_offset; /* current offset
+                           (incremented by each av_parser_parse()) */
+    int64_t next_frame_offset; /* offset of the next frame */
+    /* video info */
+    int pict_type; /* XXX: Put it back in AVCodecContext. */
+    /**
+     * This field is used for proper frame duration computation in lavf.
+     * It signals, how much longer the frame duration of the current frame
+     * is compared to normal frame duration.
+     *
+     * frame_duration = (1 + repeat_pict) * time_base
+     *
+     * It is used by codecs like H.264 to display telecined material.
+     */
+    int repeat_pict; /* XXX: Put it back in AVCodecContext. */
+    int64_t pts;     /* pts of the current frame */
+    int64_t dts;     /* dts of the current frame */
+
+    /* private data */
+    int64_t last_pts;
+    int64_t last_dts;
+    int fetch_timestamp;
+
+#define AV_PARSER_PTS_NB 4
+    int cur_frame_start_index;
+    int64_t cur_frame_offset[AV_PARSER_PTS_NB];
+    int64_t cur_frame_pts[AV_PARSER_PTS_NB];
+    int64_t cur_frame_dts[AV_PARSER_PTS_NB];
+
+    int flags;
+#define PARSER_FLAG_COMPLETE_FRAMES           0x0001
+#define PARSER_FLAG_ONCE                      0x0002
+/// Set if the parser has a valid file offset
+#define PARSER_FLAG_FETCHED_OFFSET            0x0004
+#define PARSER_FLAG_USE_CODEC_TS              0x1000
+
+    int64_t offset;      ///< byte offset from starting packet start
+    int64_t cur_frame_end[AV_PARSER_PTS_NB];
+
+    /**
+     * Set by parser to 1 for key frames and 0 for non-key frames.
+     * It is initialized to -1, so if the parser doesn't set this flag,
+     * old-style fallback using AV_PICTURE_TYPE_I picture type as key frames
+     * will be used.
+     */
+    int key_frame;
+
+    // Timestamp generation support:
+    /**
+     * Synchronization point for start of timestamp generation.
+     *
+     * Set to >0 for sync point, 0 for no sync point and <0 for undefined
+     * (default).
+     *
+     * For example, this corresponds to presence of H.264 buffering period
+     * SEI message.
+     */
+    int dts_sync_point;
+
+    /**
+     * Offset of the current timestamp against last timestamp sync point in
+     * units of AVCodecContext.time_base.
+     *
+     * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
+     * contain a valid timestamp offset.
+     *
+     * Note that the timestamp of sync point has usually a nonzero
+     * dts_ref_dts_delta, which refers to the previous sync point. Offset of
+     * the next frame after timestamp sync point will be usually 1.
+     *
+     * For example, this corresponds to H.264 cpb_removal_delay.
+     */
+    int dts_ref_dts_delta;
+
+    /**
+     * Presentation delay of current frame in units of AVCodecContext.time_base.
+     *
+     * Set to INT_MIN when dts_sync_point unused. Otherwise, it must
+     * contain valid non-negative timestamp delta (presentation time of a frame
+     * must not lie in the past).
+     *
+     * This delay represents the difference between decoding and presentation
+     * time of the frame.
+     *
+     * For example, this corresponds to H.264 dpb_output_delay.
+     */
+    int pts_dts_delta;
+
+    /**
+     * Position of the packet in file.
+     *
+     * Analogous to cur_frame_pts/dts
+     */
+    int64_t cur_frame_pos[AV_PARSER_PTS_NB];
+
+    /**
+     * Byte position of currently parsed frame in stream.
+     */
+    int64_t pos;
+
+    /**
+     * Previous frame byte position.
+     */
+    int64_t last_pos;
+
+    /**
+     * Duration of the current frame.
+     * For audio, this is in units of 1 / AVCodecContext.sample_rate.
+     * For all other types, this is in units of AVCodecContext.time_base.
+     */
+    int duration;
+
+    enum AVFieldOrder field_order;
+
+    /**
+     * Indicate whether a picture is coded as a frame, top field or bottom field.
+     *
+     * For example, H.264 field_pic_flag equal to 0 corresponds to
+     * AV_PICTURE_STRUCTURE_FRAME. An H.264 picture with field_pic_flag
+     * equal to 1 and bottom_field_flag equal to 0 corresponds to
+     * AV_PICTURE_STRUCTURE_TOP_FIELD.
+     */
+    enum AVPictureStructure picture_structure;
+
+    /**
+     * Picture number incremented in presentation or output order.
+     * This field may be reinitialized at the first picture of a new sequence.
+     *
+     * For example, this corresponds to H.264 PicOrderCnt.
+     */
+    int output_picture_number;
+
+    /**
+     * Dimensions of the decoded video intended for presentation.
+     */
+    int width;
+    int height;
+
+    /**
+     * Dimensions of the coded video.
+     */
+    int coded_width;
+    int coded_height;
+
+    /**
+     * The format of the coded data, corresponds to enum AVPixelFormat for video
+     * and for enum AVSampleFormat for audio.
+     *
+     * Note that a decoder can have considerable freedom in how exactly it
+     * decodes the data, so the format reported here might be different from the
+     * one returned by a decoder.
+     */
+    int format;
+} AVCodecParserContext;
+
+typedef struct AVCodecParser {
+    int codec_ids[7]; /* several codec IDs are permitted */
+    int priv_data_size;
+    int (*parser_init)(AVCodecParserContext *s);
+    /* This callback never returns an error, a negative value means that
+     * the frame start was in a previous packet. */
+    int (*parser_parse)(AVCodecParserContext *s,
+                        AVCodecContext *avctx,
+                        const uint8_t **poutbuf, int *poutbuf_size,
+                        const uint8_t *buf, int buf_size);
+    void (*parser_close)(AVCodecParserContext *s);
+    int (*split)(AVCodecContext *avctx, const uint8_t *buf, int buf_size);
+} AVCodecParser;
+
+/**
+ * Iterate over all registered codec parsers.
+ *
+ * @param opaque a pointer where libavcodec will store the iteration state. Must
+ *               point to NULL to start the iteration.
+ *
+ * @return the next registered codec parser or NULL when the iteration is
+ *         finished
+ */
+const AVCodecParser *av_parser_iterate(void **opaque);
+
+AVCodecParserContext *av_parser_init(int codec_id);
+
+/**
+ * Parse a packet.
+ *
+ * @param s             parser context.
+ * @param avctx         codec context.
+ * @param poutbuf       set to pointer to parsed buffer or NULL if not yet finished.
+ * @param poutbuf_size  set to size of parsed buffer or zero if not yet finished.
+ * @param buf           input buffer.
+ * @param buf_size      buffer size in bytes without the padding. I.e. the full buffer
+                        size is assumed to be buf_size + AV_INPUT_BUFFER_PADDING_SIZE.
+                        To signal EOF, this should be 0 (so that the last frame
+                        can be output).
+ * @param pts           input presentation timestamp.
+ * @param dts           input decoding timestamp.
+ * @param pos           input byte position in stream.
+ * @return the number of bytes of the input bitstream used.
+ *
+ * Example:
+ * @code
+ *   while(in_len){
+ *       len = av_parser_parse2(myparser, AVCodecContext, &data, &size,
+ *                                        in_data, in_len,
+ *                                        pts, dts, pos);
+ *       in_data += len;
+ *       in_len  -= len;
+ *
+ *       if(size)
+ *          decode_frame(data, size);
+ *   }
+ * @endcode
+ */
+int av_parser_parse2(AVCodecParserContext *s,
+                     AVCodecContext *avctx,
+                     uint8_t **poutbuf, int *poutbuf_size,
+                     const uint8_t *buf, int buf_size,
+                     int64_t pts, int64_t dts,
+                     int64_t pos);
+
+void av_parser_close(AVCodecParserContext *s);
+
+/**
+ * @}
+ * @}
+ */
+
+/**
+ * @addtogroup lavc_encoding
+ * @{
+ */
+
+int avcodec_encode_subtitle(AVCodecContext *avctx, uint8_t *buf, int buf_size,
+                            const AVSubtitle *sub);
+
+
+/**
+ * @}
+ */
+
+/**
+ * @defgroup lavc_misc Utility functions
+ * @ingroup libavc
+ *
+ * Miscellaneous utility functions related to both encoding and decoding
+ * (or neither).
+ * @{
+ */
+
+/**
+ * @defgroup lavc_misc_pixfmt Pixel formats
+ *
+ * Functions for working with pixel formats.
+ * @{
+ */
+
+/**
+ * Return a value representing the fourCC code associated to the
+ * pixel format pix_fmt, or 0 if no associated fourCC code can be
+ * found.
+ */
+unsigned int avcodec_pix_fmt_to_codec_tag(enum AVPixelFormat pix_fmt);
+
+/**
+ * Find the best pixel format to convert to given a certain source pixel
+ * format.  When converting from one pixel format to another, information loss
+ * may occur.  For example, when converting from RGB24 to GRAY, the color
+ * information will be lost. Similarly, other losses occur when converting from
+ * some formats to other formats. avcodec_find_best_pix_fmt_of_2() searches which of
+ * the given pixel formats should be used to suffer the least amount of loss.
+ * The pixel formats from which it chooses one, are determined by the
+ * pix_fmt_list parameter.
+ *
+ *
+ * @param[in] pix_fmt_list AV_PIX_FMT_NONE terminated array of pixel formats to choose from
+ * @param[in] src_pix_fmt source pixel format
+ * @param[in] has_alpha Whether the source pixel format alpha channel is used.
+ * @param[out] loss_ptr Combination of flags informing you what kind of losses will occur.
+ * @return The best pixel format to convert to or -1 if none was found.
+ */
+enum AVPixelFormat avcodec_find_best_pix_fmt_of_list(const enum AVPixelFormat *pix_fmt_list,
+                                            enum AVPixelFormat src_pix_fmt,
+                                            int has_alpha, int *loss_ptr);
+
+enum AVPixelFormat avcodec_default_get_format(struct AVCodecContext *s, const enum AVPixelFormat * fmt);
+
+/**
+ * @}
+ */
+
+void avcodec_string(char *buf, int buf_size, AVCodecContext *enc, int encode);
+
+int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2),void *arg, int *ret, int count, int size);
+int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2, int, int),void *arg, int *ret, int count);
+//FIXME func typedef
+
+/**
+ * Fill AVFrame audio data and linesize pointers.
+ *
+ * The buffer buf must be a preallocated buffer with a size big enough
+ * to contain the specified samples amount. The filled AVFrame data
+ * pointers will point to this buffer.
+ *
+ * AVFrame extended_data channel pointers are allocated if necessary for
+ * planar audio.
+ *
+ * @param frame       the AVFrame
+ *                    frame->nb_samples must be set prior to calling the
+ *                    function. This function fills in frame->data,
+ *                    frame->extended_data, frame->linesize[0].
+ * @param nb_channels channel count
+ * @param sample_fmt  sample format
+ * @param buf         buffer to use for frame data
+ * @param buf_size    size of buffer
+ * @param align       plane size sample alignment (0 = default)
+ * @return            >=0 on success, negative error code on failure
+ * @todo return the size in bytes required to store the samples in
+ * case of success, at the next libavutil bump
+ */
+int avcodec_fill_audio_frame(AVFrame *frame, int nb_channels,
+                             enum AVSampleFormat sample_fmt, const uint8_t *buf,
+                             int buf_size, int align);
+
+/**
+ * Reset the internal codec state / flush internal buffers. Should be called
+ * e.g. when seeking or when switching to a different stream.
+ *
+ * @note for decoders, this function just releases any references the decoder
+ * might keep internally, but the caller's references remain valid.
+ *
+ * @note for encoders, this function will only do something if the encoder
+ * declares support for AV_CODEC_CAP_ENCODER_FLUSH. When called, the encoder
+ * will drain any remaining packets, and can then be re-used for a different
+ * stream (as opposed to sending a null frame which will leave the encoder
+ * in a permanent EOF state after draining). This can be desirable if the
+ * cost of tearing down and replacing the encoder instance is high.
+ */
+void avcodec_flush_buffers(AVCodecContext *avctx);
+
+/**
+ * Return audio frame duration.
+ *
+ * @param avctx        codec context
+ * @param frame_bytes  size of the frame, or 0 if unknown
+ * @return             frame duration, in samples, if known. 0 if not able to
+ *                     determine.
+ */
+int av_get_audio_frame_duration(AVCodecContext *avctx, int frame_bytes);
+
+/* memory */
+
+/**
+ * Same behaviour av_fast_malloc but the buffer has additional
+ * AV_INPUT_BUFFER_PADDING_SIZE at the end which will always be 0.
+ *
+ * In addition the whole buffer will initially and after resizes
+ * be 0-initialized so that no uninitialized data will ever appear.
+ */
+void av_fast_padded_malloc(void *ptr, unsigned int *size, size_t min_size);
+
+/**
+ * Same behaviour av_fast_padded_malloc except that buffer will always
+ * be 0-initialized after call.
+ */
+void av_fast_padded_mallocz(void *ptr, unsigned int *size, size_t min_size);
+
+/**
+ * @return a positive value if s is open (i.e. avcodec_open2() was called on it
+ * with no corresponding avcodec_close()), 0 otherwise.
+ */
+int avcodec_is_open(AVCodecContext *s);
+
+/**
+ * @}
+ */
+
+#endif /* AVCODEC_AVCODEC_H */