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+/*
+ * Copyright (c) 2016, Alliance for Open Media. All rights reserved
+ *
+ * This source code is subject to the terms of the BSD 2 Clause License and
+ * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+ * was not distributed with this source code in the LICENSE file, you can
+ * obtain it at www.aomedia.org/license/software. If the Alliance for Open
+ * Media Patent License 1.0 was not distributed with this source code in the
+ * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+ */
+
+// Simple Decoder
+// ==============
+//
+// This is an example of a simple decoder loop. It takes an input file
+// containing the compressed data (in IVF format), passes it through the
+// decoder, and writes the decompressed frames to disk. Other decoder
+// examples build upon this one.
+//
+// The details of the IVF format have been elided from this example for
+// simplicity of presentation, as IVF files will not generally be used by
+// your application. In general, an IVF file consists of a file header,
+// followed by a variable number of frames. Each frame consists of a frame
+// header followed by a variable length payload. The length of the payload
+// is specified in the first four bytes of the frame header. The payload is
+// the raw compressed data.
+//
+// Standard Includes
+// -----------------
+// For decoders, you only have to include `aom_decoder.h` and then any
+// header files for the specific codecs you use. In this case, we're using
+// aom.
+//
+// Initializing The Codec
+// ----------------------
+// The libaom decoder is initialized by the call to aom_codec_dec_init().
+// Determining the codec interface to use is handled by AvxVideoReader and the
+// functions prefixed with aom_video_reader_. Discussion of those functions is
+// beyond the scope of this example, but the main gist is to open the input file
+// and parse just enough of it to determine if it's a AVx file and which AVx
+// codec is contained within the file.
+// Note the NULL pointer passed to aom_codec_dec_init(). We do that in this
+// example because we want the algorithm to determine the stream configuration
+// (width/height) and allocate memory automatically.
+//
+// Decoding A Frame
+// ----------------
+// Once the frame has been read into memory, it is decoded using the
+// `aom_codec_decode` function. The call takes a pointer to the data
+// (`frame`) and the length of the data (`frame_size`). No application data
+// is associated with the frame in this example, so the `user_priv`
+// parameter is NULL.
+//
+// Codecs may produce a variable number of output frames for every call to
+// `aom_codec_decode`. These frames are retrieved by the
+// `aom_codec_get_frame` iterator function. The iterator variable `iter` is
+// initialized to NULL each time `aom_codec_decode` is called.
+// `aom_codec_get_frame` is called in a loop, returning a pointer to a
+// decoded image or NULL to indicate the end of list.
+//
+// Processing The Decoded Data
+// ---------------------------
+// In this example, we simply write the encoded data to disk. It is
+// important to honor the image's `stride` values.
+//
+// Cleanup
+// -------
+// The `aom_codec_destroy` call frees any memory allocated by the codec.
+//
+// Error Handling
+// --------------
+// This example does not special case any error return codes. If there was
+// an error, a descriptive message is printed and the program exits. With
+// few exceptions, aom_codec functions return an enumerated error status,
+// with the value `0` indicating success.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "aom/aom_decoder.h"
+#include "common/tools_common.h"
+#include "common/video_reader.h"
+
+static const char *exec_name;
+
+void usage_exit(void) {
+  fprintf(stderr, "Usage: %s <infile> <outfile>\n", exec_name);
+  exit(EXIT_FAILURE);
+}
+
+int main(int argc, char **argv) {
+  int frame_cnt = 0;
+  FILE *outfile = NULL;
+  aom_codec_ctx_t codec;
+  AvxVideoReader *reader = NULL;
+  const AvxInterface *decoder = NULL;
+  const AvxVideoInfo *info = NULL;
+
+  exec_name = argv[0];
+
+  if (argc != 3) die("Invalid number of arguments.");
+
+  reader = aom_video_reader_open(argv[1]);
+  if (!reader) die("Failed to open %s for reading.", argv[1]);
+
+  if (!(outfile = fopen(argv[2], "wb")))
+    die("Failed to open %s for writing.", argv[2]);
+
+  info = aom_video_reader_get_info(reader);
+
+  decoder = get_aom_decoder_by_fourcc(info->codec_fourcc);
+  if (!decoder) die("Unknown input codec.");
+
+  printf("Using %s\n", aom_codec_iface_name(decoder->codec_interface()));
+
+  if (aom_codec_dec_init(&codec, decoder->codec_interface(), NULL, 0))
+    die_codec(&codec, "Failed to initialize decoder.");
+
+  while (aom_video_reader_read_frame(reader)) {
+    aom_codec_iter_t iter = NULL;
+    aom_image_t *img = NULL;
+    size_t frame_size = 0;
+    const unsigned char *frame =
+        aom_video_reader_get_frame(reader, &frame_size);
+    if (aom_codec_decode(&codec, frame, frame_size, NULL))
+      die_codec(&codec, "Failed to decode frame.");
+
+    while ((img = aom_codec_get_frame(&codec, &iter)) != NULL) {
+      aom_img_write(img, outfile);
+      ++frame_cnt;
+    }
+  }
+
+  printf("Processed %d frames.\n", frame_cnt);
+  if (aom_codec_destroy(&codec)) die_codec(&codec, "Failed to destroy codec");
+
+  printf("Play: ffplay -f rawvideo -pix_fmt yuv420p -s %dx%d %s\n",
+         info->frame_width, info->frame_height, argv[2]);
+
+  aom_video_reader_close(reader);
+
+  fclose(outfile);
+
+  return EXIT_SUCCESS;
+}