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| -rw-r--r-- | dom/media/mp3/MP3FrameParser.h | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/dom/media/mp3/MP3FrameParser.h b/dom/media/mp3/MP3FrameParser.h new file mode 100644 index 0000000000..d0d7a372d2 --- /dev/null +++ b/dom/media/mp3/MP3FrameParser.h @@ -0,0 +1,374 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef MP3_FRAME_PARSER_H_ +#define MP3_FRAME_PARSER_H_ + +#include <vector> + +#include "mozilla/Maybe.h" +#include "mozilla/Result.h" +#include "BufferReader.h" + +namespace mozilla { + +// ID3 header parser state machine used by FrameParser. +// The header contains the following format (one byte per term): +// 'I' 'D' '3' MajorVersion MinorVersion Flags Size1 Size2 Size3 Size4 +// For more details see https://id3.org/id3v2.4.0-structure +class ID3Parser { + public: + // Holds the ID3 header and its parsing state. + class ID3Header { + public: + // The header size is static, see class comment. + static const int SIZE = 10; + static const int ID3v1_SIZE = 128; + + // Constructor. + ID3Header(); + + // Resets the state to allow for a new parsing session. + void Reset(); + + // The ID3 tags are versioned like this: ID3vMajorVersion.MinorVersion. + uint8_t MajorVersion() const; + uint8_t MinorVersion() const; + + // The ID3 flags field. + uint8_t Flags() const; + + // The derived size based on the provided size fields. + uint32_t Size() const; + + // To see whether we have parsed the value of the size from header. + bool HasSizeBeenSet() const; + + // Returns the size of an ID3v2.4 footer if present and zero otherwise. + uint8_t FooterSize() const; + + // The total size of the ID3 tag including header/footer, or zero if + // none has been found. + uint32_t TotalTagSize() const; + + // Returns whether the parsed data is a valid ID3 header up to the given + // byte position. + bool IsValid(int aPos) const; + + // Returns whether the parsed data is a complete and valid ID3 header. + bool IsValid() const; + + // Parses the next provided byte. + // Returns whether the byte creates a valid sequence up to this point. + bool ParseNext(uint8_t c); + + private: + // Updates the parser state machine with the provided next byte. + // Returns whether the provided byte is a valid next byte in the sequence. + bool Update(uint8_t c); + + // The currently parsed byte sequence. + uint8_t mRaw[SIZE] = {}; + + // The derived size as provided by the size fields. + // The header size fields holds a 4 byte sequence with each MSB set to 0, + // this bits need to be ignored when deriving the actual size. + Maybe<uint32_t> mSize; + + // The current byte position in the parsed sequence. Reset via Reset and + // incremented via Update. + int mPos = 0; + }; + + // Check if the buffer is starting with ID3v2 tag. + static bool IsBufferStartingWithID3Tag(BufferReader* aReader); + // Similarly, if the buffer is starting with ID3v1 tag. + static bool IsBufferStartingWithID3v1Tag(BufferReader* aReader); + + // Returns the parsed ID3 header. Note: check for validity. + const ID3Header& Header() const; + + // Returns the size of all parsed ID3 headers. + uint32_t TotalHeadersSize() const; + + // Parses contents of given BufferReader for a valid ID3v2 header. + // Returns the parsed ID3v2 tag size if successful and zero otherwise. + uint32_t Parse(BufferReader* aReader); + + // Resets the state to allow for a new parsing session. + void Reset(); + + private: + uint32_t ParseInternal(BufferReader* aReader); + + // The currently parsed ID3 header. Reset via Reset, updated via Parse. + ID3Header mHeader; + // If a file contains multiple ID3 headers, then we would only select the + // latest one, but keep the size of former abandoned in order to return the + // correct size offset. + uint32_t mFormerID3Size = 0; +}; + +// MPEG audio frame parser. +// The MPEG frame header has the following format (one bit per character): +// 11111111 111VVLLC BBBBSSPR MMEETOHH +// { sync } - 11 sync bits +// VV - MPEG audio version ID (0->2.5, 1->reserved, 2->2, 3->1) +// LL - Layer description (0->reserved, 1->III, 2->II, 3->I) +// C - CRC protection bit (0->protected, 1->not protected) +// BBBB - Bitrate index (see table in implementation) +// SS - Sampling rate index (see table in implementation) +// P - Padding bit (0->not padded, 1->padded by 1 slot size) +// R - Private bit (ignored) +// MM - Channel mode (0->stereo, 1->joint stereo, 2->dual channel, +// 3->single channel) +// EE - Mode extension for joint stereo (ignored) +// T - Copyright (0->disabled, 1->enabled) +// O - Original (0->copy, 1->original) +// HH - Emphasis (0->none, 1->50/15 ms, 2->reserved, 3->CCIT J.17) +class FrameParser { + public: + // Holds the frame header and its parsing state. + class FrameHeader { + public: + // The header size is static, see class comments. + static const int SIZE = 4; + + // Constructor. + FrameHeader(); + + // Raw field access, see class comments for details. + uint8_t Sync1() const; + uint8_t Sync2() const; + uint8_t RawVersion() const; + uint8_t RawLayer() const; + uint8_t RawProtection() const; + uint8_t RawBitrate() const; + uint8_t RawSampleRate() const; + uint8_t Padding() const; + uint8_t Private() const; + uint8_t RawChannelMode() const; + + // Sampling rate frequency in Hz. + uint32_t SampleRate() const; + + // Number of audio channels. + uint32_t Channels() const; + + // Samples per frames, static depending on MPEG version and layer. + uint32_t SamplesPerFrame() const; + + // Slot size used for padding, static depending on MPEG layer. + uint32_t SlotSize() const; + + // Bitrate in kbps, can vary between frames. + uint32_t Bitrate() const; + + // MPEG layer (0->invalid, 1->I, 2->II, 3->III). + uint32_t Layer() const; + + // Returns whether the parsed data is a valid frame header up to the given + // byte position. + bool IsValid(const int aPos) const; + + // Returns whether the parsed data is a complete and valid frame header. + bool IsValid() const; + + // Resets the state to allow for a new parsing session. + void Reset(); + + // Parses the next provided byte. + // Returns whether the byte creates a valid sequence up to this point. + bool ParseNext(const uint8_t c); + + private: + // Updates the parser state machine with the provided next byte. + // Returns whether the provided byte is a valid next byte in the sequence. + bool Update(const uint8_t c); + + // The currently parsed byte sequence. + uint8_t mRaw[SIZE] = {}; + + // The current byte position in the parsed sequence. Reset via Reset and + // incremented via Update. + int mPos = 0; + }; + + // VBR frames may contain Xing or VBRI headers for additional info, we use + // this class to parse them and access this info. + class VBRHeader { + public: + // Synchronize with vbr_header TYPE_STR on change. + enum VBRHeaderType { NONE = 0, XING, VBRI }; + + // Constructor. + VBRHeader(); + + // Returns the parsed VBR header type, or NONE if no valid header found. + VBRHeaderType Type() const; + + // Returns the total number of audio frames (excluding the VBR header frame) + // expected in the stream/file. + const Maybe<uint32_t>& NumAudioFrames() const; + + // Returns the expected size of the stream. + const Maybe<uint32_t>& NumBytes() const; + + // Returns the VBR scale factor (0: best quality, 100: lowest quality). + const Maybe<uint32_t>& Scale() const; + + // Returns true iff Xing/Info TOC (table of contents) is present. + bool IsTOCPresent() const; + + // Returns whether the header is valid (type XING or VBRI). + bool IsValid() const; + + // Returns whether the header is valid and contains reasonable non-zero + // field values. + bool IsComplete() const; + + // Returns the byte offset for the given duration percentage as a factor + // (0: begin, 1.0: end). + int64_t Offset(media::TimeUnit aTime, media::TimeUnit aDuration) const; + + // Parses contents of given ByteReader for a valid VBR header. + // The offset of the passed ByteReader needs to point to an MPEG frame + // begin, as a VBRI-style header is searched at a fixed offset relative to + // frame begin. Returns whether a valid VBR header was found in the range. + bool Parse(BufferReader* aReader, size_t aFrameSize); + + uint32_t EncoderDelay() const { return mEncoderDelay; } + uint32_t EncoderPadding() const { return mEncoderPadding; } + + private: + // Parses contents of given ByteReader for a valid Xing header. + // The initial ByteReader offset will be preserved. + // Returns whether a valid Xing header was found in the range. + Result<bool, nsresult> ParseXing(BufferReader* aReader, size_t aFrameSize); + + // Parses contents of given ByteReader for a valid VBRI header. + // The initial ByteReader offset will be preserved. It also needs to point + // to the beginning of a valid MPEG frame, as VBRI headers are searched + // at a fixed offset relative to frame begin. + // Returns whether a valid VBRI header was found in the range. + Result<bool, nsresult> ParseVBRI(BufferReader* aReader); + + // The total number of frames expected as parsed from a VBR header. + Maybe<uint32_t> mNumAudioFrames; + + // The total number of bytes expected in the stream. + Maybe<uint32_t> mNumBytes; + + // The VBR scale factor. + Maybe<uint32_t> mScale; + + // The TOC table mapping duration percentage to byte offset. + std::vector<int64_t> mTOC; + + // The detected VBR header type. + VBRHeaderType mType; + + uint16_t mVBRISeekOffsetsFramesPerEntry = 0; + + // Delay and padding values found in the LAME header. The encoder delay is a + // number of frames that has to be skipped at the beginning of the stream, + // encoder padding is a number of frames that needs to be ignored in the + // last packet. + uint16_t mEncoderDelay = 0; + uint16_t mEncoderPadding = 0; + }; + + // Frame meta container used to parse and hold a frame header and side info. + class Frame { + public: + // Returns the length of the frame excluding the header in bytes. + uint32_t Length() const; + + // Returns the parsed frame header. + const FrameHeader& Header() const; + + // Resets the frame header and data. + void Reset(); + + // Parses the next provided byte. + // Returns whether the byte creates a valid sequence up to this point. + bool ParseNext(uint8_t c); + + private: + // The currently parsed frame header. + FrameHeader mHeader; + }; + + // Constructor. + FrameParser(); + + // Returns the currently parsed frame. Reset via Reset or EndFrameSession. + const Frame& CurrentFrame() const; + + // Returns the previously parsed frame. Reset via Reset. + const Frame& PrevFrame() const; + + // Returns the first parsed frame. Reset via Reset. + const Frame& FirstFrame() const; + + // Returns the parsed ID3 header. Note: check for validity. + const ID3Parser::ID3Header& ID3Header() const; + + // Returns whether ID3 metadata have been found, at the end of the file. + bool ID3v1MetadataFound() const; + + // Returns the size of all parsed ID3 headers. + uint32_t TotalID3HeaderSize() const; + + // Returns the parsed VBR header info. Note: check for validity by type. + const VBRHeader& VBRInfo() const; + + // Resets the parser. + void Reset(); + + // Resets all frame data, but not the ID3Header. + // Don't use between frames as first frame data is reset. + void ResetFrameData(); + + // Clear the last parsed frame to allow for next frame parsing, i.e.: + // - sets PrevFrame to CurrentFrame + // - resets the CurrentFrame + // - resets ID3Header if no valid header was parsed yet + void EndFrameSession(); + + // Parses contents of given BufferReader for a valid frame header and returns + // true if one was found. After returning, the variable passed to + // 'aBytesToSkip' holds the amount of bytes to be skipped (if any) in order to + // jump across a large ID3v2 tag spanning multiple buffers. + Result<bool, nsresult> Parse(BufferReader* aReader, uint32_t* aBytesToSkip); + + // Parses contents of given BufferReader for a valid VBR header. + // The offset of the passed BufferReader needs to point to an MPEG frame + // begin, as a VBRI-style header is searched at a fixed offset relative to + // frame begin. Returns whether a valid VBR header was found. + bool ParseVBRHeader(BufferReader* aReader); + + private: + // ID3 header parser. + ID3Parser mID3Parser; + + // VBR header parser. + VBRHeader mVBRHeader; + + // We keep the first parsed frame around for static info access, the + // previously parsed frame for debugging and the currently parsed frame. + Frame mFirstFrame; + Frame mFrame; + Frame mPrevFrame; + // If this is true, ID3v1 metadata have been found at the end of the file, and + // must be sustracted from the stream size in order to compute the stream + // duration, when computing the duration of a CBR file based on its length in + // bytes. This means that the duration can change at the moment we reach the + // end of the file. + bool mID3v1MetadataFound = false; +}; + +} // namespace mozilla + +#endif |