michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef MP3FrameParser_h
michael@0: #define MP3FrameParser_h
michael@0: 
michael@0: #include <stdint.h>
michael@0: 
michael@0: #include "mozilla/Mutex.h"
michael@0: #include "nsString.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: // Simple parser to tell whether we've found an ID3 header and how long it is,
michael@0: // so that we can skip it.
michael@0: // XXX maybe actually parse this stuff?
michael@0: class ID3Parser
michael@0: {
michael@0: public:
michael@0:   ID3Parser();
michael@0: 
michael@0:   void Reset();
michael@0:   bool ParseChar(char ch);
michael@0:   bool IsParsed() const;
michael@0:   uint32_t GetHeaderLength() const;
michael@0: 
michael@0: private:
michael@0:   uint32_t mCurrentChar;
michael@0:   uint32_t mHeaderLength;
michael@0: };
michael@0: 
michael@0: struct MP3Frame {
michael@0:   uint16_t mSync1 : 8;      // Always all set
michael@0:   uint16_t mProtected : 1;  // Ignored
michael@0:   uint16_t mLayer : 2;
michael@0:   uint16_t mVersion : 2;
michael@0:   uint16_t mSync2 : 3;      // Always all set
michael@0:   uint16_t mPrivate : 1;    // Ignored
michael@0:   uint16_t mPad : 1;
michael@0:   uint16_t mSampleRate : 2; // Index into mpeg_srates above
michael@0:   uint16_t mBitrate : 4;    // Index into mpeg_bitrates above
michael@0: 
michael@0:   uint16_t CalculateLength();
michael@0: };
michael@0: 
michael@0: // Buffering parser for MP3 frames.
michael@0: class MP3Parser
michael@0: {
michael@0: public:
michael@0:   MP3Parser();
michael@0: 
michael@0:   // Forget all data the parser has seen so far.
michael@0:   void Reset();
michael@0: 
michael@0:   // Parse the given byte. If we have found a frame header, return the length of
michael@0:   // the frame.
michael@0:   uint16_t ParseFrameLength(uint8_t ch);
michael@0: 
michael@0:   // Get the sample rate from the current header.
michael@0:   uint32_t GetSampleRate();
michael@0: 
michael@0:   // Get the number of samples per frame.
michael@0:   uint32_t GetSamplesPerFrame();
michael@0: 
michael@0: private:
michael@0:   uint32_t mCurrentChar;
michael@0:   union {
michael@0:     uint8_t mRaw[3];
michael@0:     MP3Frame mFrame;
michael@0:   } mData;
michael@0: };
michael@0: 
michael@0: 
michael@0: // A description of the MP3 format and its extensions is available at
michael@0: //
michael@0: //  http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
michael@0: //
michael@0: // The data in MP3 streams is split into small frames, with each frame
michael@0: // containing a fixed number of samples. The duration of a frame depends
michael@0: // on the frame's bit rate and sample rate. Both values can vary among
michael@0: // frames, so it is necessary to examine each individual frame of an MP3
michael@0: // stream to calculate the stream's overall duration.
michael@0: //
michael@0: // The MP3 frame parser extracts information from an MP3 data stream. It
michael@0: // accepts a range of frames of an MP3 stream as input, and parses all
michael@0: // frames for their duration. Callers can query the stream's overall
michael@0: // duration from the parser.
michael@0: //
michael@0: // Call the methods NotifyDataArrived or Parse to add new data. If you added
michael@0: // information for a certain stream position, you cannot go back to previous
michael@0: // positions. The parser will simply ignore the input. If you skip stream
michael@0: // positions, the duration of the related MP3 frames will be estimated from
michael@0: // the stream's average.
michael@0: //
michael@0: // The method GetDuration returns calculated duration of the stream, including
michael@0: // estimates for skipped ranges.
michael@0: //
michael@0: // All public methods are thread-safe.
michael@0: 
michael@0: class MP3FrameParser
michael@0: {
michael@0: public:
michael@0:   MP3FrameParser(int64_t aLength=-1);
michael@0: 
michael@0:   bool IsMP3() {
michael@0:     MutexAutoLock mon(mLock);
michael@0:     return mIsMP3 != NOT_MP3;
michael@0:   }
michael@0: 
michael@0:   void Parse(const char* aBuffer, uint32_t aLength, uint64_t aStreamOffset);
michael@0: 
michael@0:   // Returns the duration, in microseconds. If the entire stream has not
michael@0:   // been parsed yet, this is an estimate based on the bitrate of the
michael@0:   // frames parsed so far.
michael@0:   int64_t GetDuration();
michael@0: 
michael@0:   // Returns the offset of the first MP3 frame in the stream, or -1 of
michael@0:   // no MP3 frame has been detected yet.
michael@0:   int64_t GetMP3Offset();
michael@0: 
michael@0:   // Returns true if we've seen the whole first frame of the MP3 stream, and
michael@0:   // therefore can make an estimate on the stream duration.
michael@0:   // Otherwise, returns false.
michael@0:   bool ParsedHeaders();
michael@0: 
michael@0:   // Returns true if we know the exact duration of the MP3 stream;
michael@0:   // false otherwise.
michael@0:   bool HasExactDuration();
michael@0: 
michael@0:   // Returns true if the parser needs more data for duration estimation.
michael@0:   bool NeedsData();
michael@0: 
michael@0: private:
michael@0: 
michael@0:   // Parses aBuffer, starting at offset 0. Returns the number of bytes
michael@0:   // parsed, relative to the start of the buffer. Note this may be
michael@0:   // greater than aLength if the headers in the buffer indicate that
michael@0:   // the frame or ID3 tag extends outside of aBuffer. Returns failure
michael@0:   // if too many non-MP3 bytes are parsed.
michael@0:   nsresult ParseBuffer(const uint8_t* aBuffer,
michael@0:                        uint32_t aLength,
michael@0:                        int64_t aStreamOffset,
michael@0:                        uint32_t* aOutBytesRead);
michael@0: 
michael@0:   // A low-contention lock for protecting the parser results
michael@0:   Mutex mLock;
michael@0: 
michael@0:   // ID3 header parser. Keeps state between reads in case the header falls
michael@0:   // in between.
michael@0:   ID3Parser mID3Parser;
michael@0: 
michael@0:   // MP3 frame header parser.
michael@0:   MP3Parser mMP3Parser;
michael@0: 
michael@0:   // If we read |MAX_SKIPPED_BYTES| from the stream without finding any MP3
michael@0:   // frames, we give up and report |NOT_MP3|. Here we track the cumulative size
michael@0:   // of any ID3 headers we've seen so big ID3 sections aren't counted towards
michael@0:   // skipped bytes.
michael@0:   uint32_t mTotalID3Size;
michael@0: 
michael@0:   // All fields below are protected by mLock
michael@0: 
michael@0:   // We keep stats on the size of all the frames we've seen, as well as how many
michael@0:   // so that we can estimate the duration of the rest of the stream.
michael@0:   uint64_t mTotalFrameSize;
michael@0:   uint64_t mFrameCount;
michael@0: 
michael@0:   // Offset of the last data parsed. This is the end offset of the last data
michael@0:   // block parsed, so it's the start offset we expect to get on the next
michael@0:   // call to Parse().
michael@0:   uint64_t mOffset;
michael@0: 
michael@0:   // Total length of the stream in bytes.
michael@0:   int64_t mLength;
michael@0: 
michael@0:   // Offset of first MP3 frame in the bitstream. Has value -1 until the
michael@0:   // first MP3 frame is found.
michael@0:   int64_t mMP3Offset;
michael@0: 
michael@0:   // The exact number of frames in this stream, if we know it. -1 otherwise.
michael@0:   int64_t mNumFrames;
michael@0: 
michael@0:   // Number of audio samples per second and per frame. Fixed through the whole
michael@0:   // file. If we know these variables as well as the number of frames in the
michael@0:   // file, we can get an exact duration for the stream.
michael@0:   uint16_t mSamplesPerSecond;
michael@0:   uint16_t mSamplesPerFrame;
michael@0: 
michael@0:   // If the MP3 has a variable bitrate, then there *should* be metadata about
michael@0:   // the encoding in the first frame. We buffer the first frame here.
michael@0:   nsAutoCString mFirstFrame;
michael@0: 
michael@0:   // While we are reading the first frame, this is the stream offset of the
michael@0:   // last byte of that frame. -1 at all other times.
michael@0:   int64_t mFirstFrameEnd;
michael@0: 
michael@0:   enum eIsMP3 {
michael@0:     MAYBE_MP3, // We're giving the stream the benefit of the doubt...
michael@0:     DEFINITELY_MP3, // We've hit at least one ID3 tag or MP3 frame.
michael@0:     NOT_MP3 // Not found any evidence of the stream being MP3.
michael@0:   };
michael@0: 
michael@0:   eIsMP3 mIsMP3;
michael@0: 
michael@0: };
michael@0: 
michael@0: }
michael@0: 
michael@0: #endif