зеркало из https://github.com/mozilla/gecko-dev.git
77 строки
2.4 KiB
C
77 строки
2.4 KiB
C
|
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
||
|
|
/* vim:set ts=2 sw=2 sts=2 et cindent: */
|
||
|
|
/* 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/. */
|
||
|
|
|
||
|
|
#include <stdint.h>
|
||
|
|
#include "mozilla/Mutex.h"
|
||
|
|
|
||
|
|
namespace mozilla {
|
||
|
|
|
||
|
|
// A description of the MP3 format and its extensions is available at
|
||
|
|
//
|
||
|
|
// http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
|
||
|
|
//
|
||
|
|
// The data in MP3 streams is split into small frames, with each frame
|
||
|
|
// containing a fixed number of samples. The duration of a frame depends
|
||
|
|
// on the frame's bit rate and sample rate. Both values can vary among
|
||
|
|
// frames, so it is necessary to examine each individual frame of an MP3
|
||
|
|
// stream to calculate the stream's overall duration.
|
||
|
|
//
|
||
|
|
// The MP3 frame parser extracts information from an MP3 data stream. It
|
||
|
|
// accepts a range of frames of an MP3 stream as input, and parses all
|
||
|
|
// frames for their duration. Callers can query the stream's overall
|
||
|
|
// duration from the parser.
|
||
|
|
//
|
||
|
|
// Call the methods NotifyDataArrived or Parse to add new data. If you added
|
||
|
|
// information for a certain stream position, you cannot go back to previous
|
||
|
|
// positions. The parser will simply ignore the input. If you skip stream
|
||
|
|
// positions, the duration of the related MP3 frames will be estimated from
|
||
|
|
// the stream's average.
|
||
|
|
//
|
||
|
|
// The method GetDuration returns calculated duration of the stream, including
|
||
|
|
// estimates for skipped ranges.
|
||
|
|
//
|
||
|
|
// All public methods are thread-safe.
|
||
|
|
|
||
|
|
class MP3FrameParser
|
||
|
|
{
|
||
|
|
public:
|
||
|
|
MP3FrameParser(int64_t aLength=-1);
|
||
|
|
|
||
|
|
bool IsMP3() {
|
||
|
|
MutexAutoLock mon(mLock);
|
||
|
|
return mIsMP3;
|
||
|
|
}
|
||
|
|
|
||
|
|
void Parse(const uint8_t* aBuffer, uint32_t aLength, int64_t aOffset);
|
||
|
|
|
||
|
|
void NotifyDataArrived(const char* aBuffer, uint32_t aLength, int64_t aOffset);
|
||
|
|
|
||
|
|
int64_t GetDuration();
|
||
|
|
|
||
|
|
private:
|
||
|
|
size_t ParseInternalBuffer(const uint8_t* aBuffer, uint32_t aLength, int64_t aOffset);
|
||
|
|
|
||
|
|
uint8_t mBuffer[10];
|
||
|
|
uint32_t mBufferLength;
|
||
|
|
|
||
|
|
// A low-contention lock for protecting the parser results
|
||
|
|
Mutex mLock;
|
||
|
|
|
||
|
|
// All fields below are protected by mLock
|
||
|
|
uint64_t mDurationUs;
|
||
|
|
uint64_t mBitRateSum;
|
||
|
|
uint64_t mNumFrames;
|
||
|
|
int64_t mOffset;
|
||
|
|
int64_t mUnhandled;
|
||
|
|
int64_t mLength;
|
||
|
|
uint32_t mTrailing;
|
||
|
|
|
||
|
|
// Contains the state of the MP3 detection
|
||
|
|
bool mIsMP3;
|
||
|
|
};
|
||
|
|
|
||
|
|
}
|