Macintosh-SW
/
tenfourfox
mirror of https://github.com/classilla/tenfourfox.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
tenfourfox/dom/media/MP3FrameParser.cpp

597 lines
17 KiB
C++
Raw Permalink Blame History

/* -*- 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 <algorithm>
#include "nsMemory.h"
#include "MP3FrameParser.h"
#include "VideoUtils.h"
#if __ppc__
#define FROM_BIG_ENDIAN(X) (X)
#else
// Nuh-uh.
#define FROM_BIG_ENDIAN(X) ((uint32_t)((uint8_t)(X)[0] << 24 | (uint8_t)(X)[1] << 16 | \
(uint8_t)(X)[2] << 8 | (uint8_t)(X)[3]))
#endif
namespace mozilla {
/*
* Following code taken from http://www.hydrogenaudio.org/forums/index.php?showtopic=85125
* with permission from the author, Nick Wallette <sirnickity@gmail.com>.
*/
/* BEGIN shameless copy and paste */
// Bitrates - use [version][layer][bitrate]
const uint16_t mpeg_bitrates[4][4][16] = {
{ // Version 2.5
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 3
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 2
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 } // Layer 1
},
{ // Reserved
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } // Invalid
},
{ // Version 2
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 3
{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 2
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 } // Layer 1
},
{ // Version 1
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
{ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0 }, // Layer 3
{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 }, // Layer 2
{ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0 }, // Layer 1
}
};
// Sample rates - use [version][srate]
const uint16_t mpeg_srates[4][4] = {
{ 11025, 12000, 8000, 0 }, // MPEG 2.5
{ 0, 0, 0, 0 }, // Reserved
{ 22050, 24000, 16000, 0 }, // MPEG 2
{ 44100, 48000, 32000, 0 } // MPEG 1
};
// Samples per frame - use [version][layer]
const uint16_t mpeg_frame_samples[4][4] = {
// Rsvd 3 2 1 < Layer v Version
{ 0, 576, 1152, 384 }, // 2.5
{ 0, 0, 0, 0 }, // Reserved
{ 0, 576, 1152, 384 }, // 2
{ 0, 1152, 1152, 384 } // 1
};
// Slot size (MPEG unit of measurement) - use [layer]
const uint8_t mpeg_slot_size[4] = { 0, 1, 1, 4 }; // Rsvd, 3, 2, 1
uint16_t
MP3Frame::CalculateLength()
{
// Lookup real values of these fields
uint32_t bitrate = mpeg_bitrates[mVersion][mLayer][mBitrate] * 1000;
uint32_t samprate = mpeg_srates[mVersion][mSampleRate];
uint16_t samples = mpeg_frame_samples[mVersion][mLayer];
uint8_t slot_size = mpeg_slot_size[mLayer];
// In-between calculations
float bps = (float)samples / 8.0;
float fsize = ( (bps * (float)bitrate) / (float)samprate )
+ ( (mPad) ? slot_size : 0 );
// Frame sizes are truncated integers
return (uint16_t)fsize;
}
/* END shameless copy and paste */
/** MP3Parser methods **/
MP3Parser::MP3Parser()
: mCurrentChar(0)
{ }
void
MP3Parser::Reset()
{
mCurrentChar = 0;
}
uint16_t
MP3Parser::ParseFrameLength(uint8_t ch)
{
mData.mRaw[mCurrentChar] = ch;
MP3Frame &frame = mData.mFrame;
// Validate MP3 header as we read. We can't mistake the start of an MP3 frame
// for the middle of another frame due to the sync byte at the beginning
// of the frame.
// The only valid position for an all-high byte is the sync byte at the
// beginning of the frame.
if (ch == 0xff) {
mCurrentChar = 0;
}
// Make sure the current byte is valid in context. If not, reset the parser.
if (mCurrentChar == 2) {
if (frame.mBitrate == 0x0f) {
goto fail;
}
} else if (mCurrentChar == 1) {
if (frame.mSync2 != 0x07
|| frame.mVersion == 0x01
|| frame.mLayer == 0x00) {
goto fail;
}
}
// The only valid character at the beginning of the header is 0xff. Fail if
// it's different.
if (mCurrentChar == 0 && frame.mSync1 != 0xff) {
// Couldn't find the sync byte. Fail.
return 0;
}
mCurrentChar++;
MOZ_ASSERT(mCurrentChar <= sizeof(MP3Frame));
// Don't have a full header yet.
if (mCurrentChar < sizeof(MP3Frame)) {
return 0;
}
// Woo, valid header. Return the length.
mCurrentChar = 0;
return frame.CalculateLength();
fail:
Reset();
return 0;
}
uint32_t
MP3Parser::GetSampleRate()
{
MP3Frame &frame = mData.mFrame;
return mpeg_srates[frame.mVersion][frame.mSampleRate];
}
uint32_t
MP3Parser::GetSamplesPerFrame()
{
MP3Frame &frame = mData.mFrame;
return mpeg_frame_samples[frame.mVersion][frame.mLayer];
}
/** ID3Parser methods **/
const char sID3Head[3] = { 'I', 'D', '3' };
const uint32_t ID3_HEADER_LENGTH = 10;
const uint32_t ID3_FOOTER_LENGTH = 10;
const uint8_t ID3_FOOTER_PRESENT = 0x10;
ID3Parser::ID3Parser()
: mCurrentChar(0)
, mVersion(0)
, mFlags(0)
, mHeaderLength(0)
{ }
void
ID3Parser::Reset()
{
mCurrentChar = mVersion = mFlags = mHeaderLength = 0;
}
bool
ID3Parser::ParseChar(char ch)
{
switch (mCurrentChar) {
// The first three bytes of an ID3v2 header must match the string "ID3".
case 0: case 1: case 2:
if (ch != sID3Head[mCurrentChar]) {
goto fail;
}
break;
// The fourth and fifth bytes give the version, between 2 and 4.
case 3:
if (ch < '\2' || ch > '\4') {
goto fail;
}
mVersion = uint8_t(ch);
break;
case 4:
if (ch != '\0') {
goto fail;
}
break;
// The sixth byte gives the flags; valid flags depend on the version.
case 5:
if ((ch & (0xff >> mVersion)) != '\0') {
goto fail;
}
mFlags = uint8_t(ch);
break;
// Bytes seven through ten give the sum of the byte length of the extended
// header, the padding and the frames after unsynchronisation.
// These bytes form a 28-bit integer, with the high bit of each byte unset.
case 6: case 7: case 8: case 9:
if (ch & 0x80) {
goto fail;
}
mHeaderLength <<= 7;
mHeaderLength |= ch;
if (mCurrentChar == 9) {
mHeaderLength += ID3_HEADER_LENGTH;
mHeaderLength += (mFlags & ID3_FOOTER_PRESENT) ? ID3_FOOTER_LENGTH : 0;
}
break;
default:
MOZ_CRASH("Header already fully parsed!");
}
mCurrentChar++;
return IsParsed();
fail:
if (mCurrentChar) {
Reset();
return ParseChar(ch);
}
Reset();
return false;
}
bool
ID3Parser::IsParsed() const
{
return mCurrentChar >= ID3_HEADER_LENGTH;
}
uint32_t
ID3Parser::GetHeaderLength() const
{
MOZ_ASSERT(IsParsed(),
"Queried length of ID3 header before parsing finished.");
return mHeaderLength;
}
/** VBR header helper stuff **/
// Helper function to find a VBR header in an MP3 frame.
// Based on information from
// http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
const uint32_t VBRI_TAG = FROM_BIG_ENDIAN("VBRI");
const uint32_t VBRI_OFFSET = 32 - sizeof(MP3Frame);
const uint32_t VBRI_FRAME_COUNT_OFFSET = VBRI_OFFSET + 14;
const uint32_t VBRI_MIN_FRAME_SIZE = VBRI_OFFSET + 26;
const uint32_t XING_TAG = FROM_BIG_ENDIAN("Xing");
enum XingFlags {
XING_HAS_NUM_FRAMES = 0x01,
XING_HAS_NUM_BYTES = 0x02,
XING_HAS_TOC = 0x04,
XING_HAS_VBR_SCALE = 0x08
};
static int64_t
ParseXing(const char *aBuffer)
{
uint32_t flags = FROM_BIG_ENDIAN(aBuffer + 4);
if (!(flags & XING_HAS_NUM_FRAMES)) {
NS_WARNING("VBR file without frame count. Duration estimation likely to "
"be totally wrong.");
return -1;
}
int64_t numFrames = -1;
if (flags & XING_HAS_NUM_FRAMES) {
numFrames = FROM_BIG_ENDIAN(aBuffer + 8);
}
return numFrames;
}
static int64_t
FindNumVBRFrames(const nsCString& aFrame)
{
const char *buffer = aFrame.get();
const char *bufferEnd = aFrame.get() + aFrame.Length();
// VBRI header is nice and well-defined; let's try to find that first.
if (aFrame.Length() > VBRI_MIN_FRAME_SIZE &&
FROM_BIG_ENDIAN(buffer + VBRI_OFFSET) == VBRI_TAG) {
return FROM_BIG_ENDIAN(buffer + VBRI_FRAME_COUNT_OFFSET);
}
// We have to search for the Xing header as its position can change.
for (; buffer + sizeof(XING_TAG) < bufferEnd; buffer++) {
if (FROM_BIG_ENDIAN(buffer) == XING_TAG) {
return ParseXing(buffer);
}
}
return -1;
}
/** MP3FrameParser methods **/
// Some MP3's have large ID3v2 tags, up to 150KB, so we allow lots of
// skipped bytes to be read, just in case, before we give up and assume
// we're not parsing an MP3 stream.
static const uint32_t MAX_SKIPPED_BYTES = 4096;
enum {
MP3_HEADER_LENGTH = 4,
};
MP3FrameParser::MP3FrameParser(int64_t aLength)
: mLock("MP3FrameParser.mLock"),
mTotalID3Size(0),
mTotalFrameSize(0),
mFrameCount(0),
mOffset(0),
mLength(aLength),
mMP3Offset(-1),
mSamplesPerSecond(0),
mFirstFrameEnd(-1),
mIsMP3(MAYBE_MP3)
{ }
nsresult MP3FrameParser::ParseBuffer(const uint8_t* aBuffer,
uint32_t aLength,
int64_t aStreamOffset,
uint32_t* aOutBytesRead)
{
// Iterate forwards over the buffer, looking for ID3 tag, or MP3
// Frame headers.
const uint8_t *buffer = aBuffer;
const uint8_t *bufferEnd = aBuffer + aLength;
// If we haven't found any MP3 frame data yet, there might be ID3 headers
// we can skip over.
if (mMP3Offset < 0) {
for (const uint8_t *ch = buffer; ch < bufferEnd; ch++) {
if (mID3Parser.ParseChar(*ch)) {
// Found an ID3 header. We don't care about the body of the header, so
// just skip past.
buffer = ch + mID3Parser.GetHeaderLength() - (ID3_HEADER_LENGTH - 1);
if (buffer <= ch) {
return NS_ERROR_FAILURE;
}
ch = buffer;
mTotalID3Size += mID3Parser.GetHeaderLength();
// Yes, this is an MP3!
mIsMP3 = DEFINITELY_MP3;
mID3Parser.Reset();
}
}
}
// The first MP3 frame in a variable bitrate stream can contain metadata
// for duration estimation and seeking, so we buffer that first frame here.
if (aStreamOffset < mFirstFrameEnd) {
uint64_t copyLen = std::min((int64_t)aLength, mFirstFrameEnd - aStreamOffset);
mFirstFrame.Append((const char *)buffer, copyLen);
buffer += copyLen;
}
while (buffer < bufferEnd) {
uint16_t frameLen = mMP3Parser.ParseFrameLength(*buffer);
if (frameLen) {
// We've found an MP3 frame!
// This is the first frame (and the only one we'll bother parsing), so:
// * Mark this stream as MP3;
// * Store the offset at which the MP3 data started; and
// * Start buffering the frame, as it might contain handy metadata.
// We're now sure this is an MP3 stream.
mIsMP3 = DEFINITELY_MP3;
// We need to know these to convert the number of frames in the stream
// to the length of the stream in seconds.
mSamplesPerSecond = mMP3Parser.GetSampleRate();
mSamplesPerFrame = mMP3Parser.GetSamplesPerFrame();
// If the stream has a constant bitrate, we should only need the length
// of the first frame and the length (in bytes) of the stream to
// estimate the length (in seconds).
mTotalFrameSize += frameLen;
mFrameCount++;
// If |mMP3Offset| isn't set then this is the first MP3 frame we have
// seen in the stream, which is useful for duration estimation.
if (mMP3Offset > -1) {
uint16_t skip = frameLen - sizeof(MP3Frame);
buffer += skip ? skip : 1;
continue;
}
// Remember the offset of the MP3 stream.
// We're at the last byte of an MP3Frame, so MP3 data started
// sizeof(MP3Frame) - 1 bytes ago.
mMP3Offset = aStreamOffset
+ (buffer - aBuffer)
- (sizeof(MP3Frame) - 1);
buffer++;
// If the stream has a variable bitrate, the first frame has metadata
// we need for duration estimation and seeking. Start buffering it so we
// can parse it later.
mFirstFrameEnd = mMP3Offset + frameLen;
uint64_t currOffset = buffer - aBuffer + aStreamOffset;
uint64_t copyLen = std::min(mFirstFrameEnd - currOffset,
(uint64_t)(bufferEnd - buffer));
mFirstFrame.Append((const char *)buffer, copyLen);
buffer += copyLen;
} else {
// Nothing to see here. Move along.
buffer++;
}
}
*aOutBytesRead = buffer - aBuffer;
if (mFirstFrameEnd > -1 && mFirstFrameEnd <= aStreamOffset + buffer - aBuffer) {
// We have our whole first frame. Try to find a VBR header.
mNumFrames = FindNumVBRFrames(mFirstFrame);
mFirstFrameEnd = -1;
}
return NS_OK;
}
void MP3FrameParser::Parse(const uint8_t* aBuffer, uint32_t aLength, uint64_t aOffset)
{
MutexAutoLock mon(mLock);
if (HasExactDuration()) {
// We know the duration; nothing to do here.
return;
}
const uint8_t* buffer = aBuffer;
int32_t length = aLength;
uint64_t offset = aOffset;
// Got some data we have seen already. Skip forward to what we need.
if (aOffset < mOffset) {
buffer += mOffset - aOffset;
length -= mOffset - aOffset;
offset = mOffset;
if (length <= 0) {
return;
}
}
// If there is a discontinuity in the input stream, reset the state of the
// parsers so we don't get any partial headers.
if (mOffset < aOffset) {
if (!mID3Parser.IsParsed()) {
// Only reset this if it hasn't finished yet.
mID3Parser.Reset();
}
if (mFirstFrameEnd > -1) {
NS_WARNING("Discontinuity in input while buffering first frame.");
mFirstFrameEnd = -1;
}
mMP3Parser.Reset();
}
uint32_t bytesRead = 0;
if (NS_FAILED(ParseBuffer(buffer,
length,
offset,
&bytesRead))) {
return;
}
MOZ_ASSERT(length <= (int)bytesRead, "All bytes should have been consumed");
// Update next data offset
mOffset = offset + bytesRead;
// If we've parsed lots of data and we still have nothing, just give up.
// We don't count ID3 headers towards the skipped bytes count, as MP3 files
// can have massive ID3 sections.
if (!mID3Parser.IsParsed() && mMP3Offset < 0 &&
mOffset - mTotalID3Size > MAX_SKIPPED_BYTES) {
mIsMP3 = NOT_MP3;
}
}
int64_t MP3FrameParser::GetDuration()
{
MutexAutoLock mon(mLock);
if (!ParsedHeaders() || !mSamplesPerSecond) {
// Not a single frame decoded yet.
return -1;
}
MOZ_ASSERT(mFrameCount > 0 && mTotalFrameSize > 0,
"Frame parser should have seen at least one MP3 frame of positive length.");
if (!mFrameCount || !mTotalFrameSize) {
// This should never happen.
return -1;
}
double frames;
if (mNumFrames < 0) {
// Estimate the number of frames in the stream based on the average frame
// size and the length of the MP3 file.
double frameSize = (double)mTotalFrameSize / mFrameCount;
frames = (double)(mLength - mMP3Offset) / frameSize;
} else {
// We know the exact number of frames from the VBR header.
frames = mNumFrames;
}
// The duration of each frame is constant over a given stream.
double usPerFrame = USECS_PER_S * mSamplesPerFrame / mSamplesPerSecond;
return frames * usPerFrame;
}
int64_t MP3FrameParser::GetMP3Offset()
{
MutexAutoLock mon(mLock);
return mMP3Offset;
}
bool MP3FrameParser::ParsedHeaders()
{
// We have seen both the beginning and the end of the first MP3 frame in the
// stream.
return mMP3Offset > -1 && mFirstFrameEnd < 0;
}
bool MP3FrameParser::HasExactDuration()
{
return ParsedHeaders() && mNumFrames > -1;
}
bool MP3FrameParser::NeedsData()
{
// If we don't know the duration exactly then either:
// - we're still waiting for a VBR header; or
// - we look at all frames to constantly update our duration estimate.
return IsMP3() && !HasExactDuration();
}
} // namespace mozilla
Reference in New Issue View Git Blame Copy Permalink