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558 lines
16 KiB
C++
558 lines
16 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include <algorithm>
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#include "nsMemory.h"
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#include "MP3FrameParser.h"
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#include "VideoUtils.h"
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#define FROM_BIG_ENDIAN(X) ((uint32_t)((uint8_t)(X)[0] << 24 | (uint8_t)(X)[1] << 16 | \
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(uint8_t)(X)[2] << 8 | (uint8_t)(X)[3]))
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namespace mozilla {
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/*
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* Following code taken from http://www.hydrogenaudio.org/forums/index.php?showtopic=85125
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* with permission from the author, Nick Wallette <sirnickity@gmail.com>.
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*/
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/* BEGIN shameless copy and paste */
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// Bitrates - use [version][layer][bitrate]
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const uint16_t mpeg_bitrates[4][4][16] = {
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{ // Version 2.5
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 3
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 2
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 } // Layer 1
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},
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{ // Reserved
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Invalid
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } // Invalid
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},
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{ // Version 2
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 3
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{ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 }, // Layer 2
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 } // Layer 1
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},
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{ // Version 1
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{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // Reserved
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{ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0 }, // Layer 3
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{ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 }, // Layer 2
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{ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0 }, // Layer 1
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}
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};
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// Sample rates - use [version][srate]
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const uint16_t mpeg_srates[4][4] = {
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{ 11025, 12000, 8000, 0 }, // MPEG 2.5
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{ 0, 0, 0, 0 }, // Reserved
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{ 22050, 24000, 16000, 0 }, // MPEG 2
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{ 44100, 48000, 32000, 0 } // MPEG 1
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};
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// Samples per frame - use [version][layer]
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const uint16_t mpeg_frame_samples[4][4] = {
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// Rsvd 3 2 1 < Layer v Version
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{ 0, 576, 1152, 384 }, // 2.5
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{ 0, 0, 0, 0 }, // Reserved
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{ 0, 576, 1152, 384 }, // 2
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{ 0, 1152, 1152, 384 } // 1
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};
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// Slot size (MPEG unit of measurement) - use [layer]
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const uint8_t mpeg_slot_size[4] = { 0, 1, 1, 4 }; // Rsvd, 3, 2, 1
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uint16_t
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MP3Frame::CalculateLength()
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{
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// Lookup real values of these fields
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uint32_t bitrate = mpeg_bitrates[mVersion][mLayer][mBitrate] * 1000;
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uint32_t samprate = mpeg_srates[mVersion][mSampleRate];
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uint16_t samples = mpeg_frame_samples[mVersion][mLayer];
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uint8_t slot_size = mpeg_slot_size[mLayer];
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// In-between calculations
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float bps = (float)samples / 8.0;
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float fsize = ( (bps * (float)bitrate) / (float)samprate )
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+ ( (mPad) ? slot_size : 0 );
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// Frame sizes are truncated integers
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return (uint16_t)fsize;
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}
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/* END shameless copy and paste */
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/** MP3Parser methods **/
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MP3Parser::MP3Parser()
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: mCurrentChar(0)
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{ }
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void
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MP3Parser::Reset()
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{
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mCurrentChar = 0;
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}
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uint16_t
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MP3Parser::ParseFrameLength(uint8_t ch)
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{
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mData.mRaw[mCurrentChar] = ch;
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MP3Frame &frame = mData.mFrame;
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// Validate MP3 header as we read. We can't mistake the start of an MP3 frame
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// for the middle of another frame due to the sync byte at the beginning
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// of the frame.
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// The only valid position for an all-high byte is the sync byte at the
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// beginning of the frame.
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if (ch == 0xff) {
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mCurrentChar = 0;
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}
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// Make sure the current byte is valid in context. If not, reset the parser.
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if (mCurrentChar == 2) {
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if (frame.mBitrate == 0x0f) {
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goto fail;
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}
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} else if (mCurrentChar == 1) {
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if (frame.mSync2 != 0x07
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|| frame.mVersion == 0x01
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|| frame.mLayer == 0x00) {
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goto fail;
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}
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}
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// The only valid character at the beginning of the header is 0xff. Fail if
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// it's different.
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if (mCurrentChar == 0 && frame.mSync1 != 0xff) {
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// Couldn't find the sync byte. Fail.
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return 0;
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}
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mCurrentChar++;
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MOZ_ASSERT(mCurrentChar <= sizeof(MP3Frame));
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// Don't have a full header yet.
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if (mCurrentChar < sizeof(MP3Frame)) {
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return 0;
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}
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// Woo, valid header. Return the length.
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mCurrentChar = 0;
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return frame.CalculateLength();
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fail:
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Reset();
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return 0;
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}
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uint32_t
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MP3Parser::GetSampleRate()
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{
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MP3Frame &frame = mData.mFrame;
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return mpeg_srates[frame.mVersion][frame.mSampleRate];
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}
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uint32_t
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MP3Parser::GetSamplesPerFrame()
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{
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MP3Frame &frame = mData.mFrame;
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return mpeg_frame_samples[frame.mVersion][frame.mLayer];
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}
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/** ID3Parser methods **/
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const char sID3Head[3] = { 'I', 'D', '3' };
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const uint32_t ID3_HEADER_LENGTH = 10;
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ID3Parser::ID3Parser()
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: mCurrentChar(0)
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, mHeaderLength(0)
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{ }
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void
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ID3Parser::Reset()
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{
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mCurrentChar = mHeaderLength = 0;
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}
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bool
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ID3Parser::ParseChar(char ch)
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{
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// First three bytes of an ID3v2 header must match the string "ID3".
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if (mCurrentChar < sizeof(sID3Head) / sizeof(*sID3Head)
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&& ch != sID3Head[mCurrentChar]) {
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goto fail;
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}
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// The last four bytes of the header is a 28-bit unsigned integer with the
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// high bit of each byte unset.
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if (mCurrentChar >= 6 && mCurrentChar < ID3_HEADER_LENGTH) {
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if (ch & 0x80) {
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goto fail;
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} else {
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mHeaderLength <<= 7;
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mHeaderLength |= ch;
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}
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}
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mCurrentChar++;
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return IsParsed();
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fail:
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Reset();
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return false;
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}
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bool
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ID3Parser::IsParsed() const
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{
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return mCurrentChar >= ID3_HEADER_LENGTH;
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}
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uint32_t
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ID3Parser::GetHeaderLength() const
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{
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MOZ_ASSERT(IsParsed(),
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"Queried length of ID3 header before parsing finished.");
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return mHeaderLength;
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}
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/** VBR header helper stuff **/
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// Helper function to find a VBR header in an MP3 frame.
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// Based on information from
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// http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
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const uint32_t VBRI_TAG = FROM_BIG_ENDIAN("VBRI");
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const uint32_t VBRI_OFFSET = 32 - sizeof(MP3Frame);
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const uint32_t VBRI_FRAME_COUNT_OFFSET = VBRI_OFFSET + 14;
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const uint32_t VBRI_MIN_FRAME_SIZE = VBRI_OFFSET + 26;
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const uint32_t XING_TAG = FROM_BIG_ENDIAN("Xing");
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enum XingFlags {
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XING_HAS_NUM_FRAMES = 0x01,
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XING_HAS_NUM_BYTES = 0x02,
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XING_HAS_TOC = 0x04,
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XING_HAS_VBR_SCALE = 0x08
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};
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static int64_t
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ParseXing(const char *aBuffer)
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{
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uint32_t flags = FROM_BIG_ENDIAN(aBuffer + 4);
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if (!(flags & XING_HAS_NUM_FRAMES)) {
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NS_WARNING("VBR file without frame count. Duration estimation likely to "
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"be totally wrong.");
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return -1;
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}
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int64_t numFrames = -1;
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if (flags & XING_HAS_NUM_FRAMES) {
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numFrames = FROM_BIG_ENDIAN(aBuffer + 8);
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}
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return numFrames;
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}
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static int64_t
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FindNumVBRFrames(const nsAutoCString& aFrame)
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{
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const char *buffer = aFrame.get();
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const char *bufferEnd = aFrame.get() + aFrame.Length();
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// VBRI header is nice and well-defined; let's try to find that first.
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if (aFrame.Length() > VBRI_MIN_FRAME_SIZE &&
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FROM_BIG_ENDIAN(buffer + VBRI_OFFSET) == VBRI_TAG) {
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return FROM_BIG_ENDIAN(buffer + VBRI_FRAME_COUNT_OFFSET);
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}
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// We have to search for the Xing header as its position can change.
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for (; buffer + sizeof(XING_TAG) < bufferEnd; buffer++) {
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if (FROM_BIG_ENDIAN(buffer) == XING_TAG) {
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return ParseXing(buffer);
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}
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}
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return -1;
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}
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/** MP3FrameParser methods **/
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// Some MP3's have large ID3v2 tags, up to 150KB, so we allow lots of
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// skipped bytes to be read, just in case, before we give up and assume
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// we're not parsing an MP3 stream.
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static const uint32_t MAX_SKIPPED_BYTES = 4096;
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// The number of audio samples per MP3 frame. This is constant over all MP3
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// streams. With this constant, the stream's sample rate, and an estimated
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// number of frames in the stream, we can estimate the stream's duration
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// fairly accurately.
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static const uint32_t SAMPLES_PER_FRAME = 1152;
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enum {
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MP3_HEADER_LENGTH = 4,
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};
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MP3FrameParser::MP3FrameParser(int64_t aLength)
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: mLock("MP3FrameParser.mLock"),
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mTotalID3Size(0),
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mTotalFrameSize(0),
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mFrameCount(0),
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mOffset(0),
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mLength(aLength),
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mMP3Offset(-1),
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mSamplesPerSecond(0),
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mFirstFrameEnd(-1),
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mIsMP3(MAYBE_MP3)
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{ }
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nsresult MP3FrameParser::ParseBuffer(const uint8_t* aBuffer,
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uint32_t aLength,
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int64_t aStreamOffset,
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uint32_t* aOutBytesRead)
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{
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// Iterate forwards over the buffer, looking for ID3 tag, or MP3
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// Frame headers.
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const uint8_t *buffer = aBuffer;
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const uint8_t *bufferEnd = aBuffer + aLength;
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// If we haven't found any MP3 frame data yet, there might be ID3 headers
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// we can skip over.
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if (mMP3Offset < 0) {
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for (const uint8_t *ch = buffer; ch < bufferEnd; ch++) {
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if (mID3Parser.ParseChar(*ch)) {
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// Found an ID3 header. We don't care about the body of the header, so
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// just skip past.
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buffer = ch + mID3Parser.GetHeaderLength() - (ID3_HEADER_LENGTH - 1);
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ch = buffer;
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mTotalID3Size += mID3Parser.GetHeaderLength();
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// Yes, this is an MP3!
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mIsMP3 = DEFINITELY_MP3;
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mID3Parser.Reset();
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}
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}
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}
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// The first MP3 frame in a variable bitrate stream can contain metadata
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// for duration estimation and seeking, so we buffer that first frame here.
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if (aStreamOffset < mFirstFrameEnd) {
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uint64_t copyLen = std::min((int64_t)aLength, mFirstFrameEnd - aStreamOffset);
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mFirstFrame.Append((const char *)buffer, copyLen);
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buffer += copyLen;
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}
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while (buffer < bufferEnd) {
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uint16_t frameLen = mMP3Parser.ParseFrameLength(*buffer);
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if (frameLen) {
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// We've found an MP3 frame!
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// This is the first frame (and the only one we'll bother parsing), so:
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// * Mark this stream as MP3;
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// * Store the offset at which the MP3 data started; and
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// * Start buffering the frame, as it might contain handy metadata.
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// We're now sure this is an MP3 stream.
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mIsMP3 = DEFINITELY_MP3;
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// We need to know these to convert the number of frames in the stream
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// to the length of the stream in seconds.
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mSamplesPerSecond = mMP3Parser.GetSampleRate();
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mSamplesPerFrame = mMP3Parser.GetSamplesPerFrame();
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// If the stream has a constant bitrate, we should only need the length
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// of the first frame and the length (in bytes) of the stream to
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// estimate the length (in seconds).
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mTotalFrameSize += frameLen;
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mFrameCount++;
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// If |mMP3Offset| isn't set then this is the first MP3 frame we have
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// seen in the stream, which is useful for duration estimation.
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if (mMP3Offset > -1) {
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uint16_t skip = frameLen - sizeof(MP3Frame);
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buffer += skip ? skip : 1;
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continue;
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}
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// Remember the offset of the MP3 stream.
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// We're at the last byte of an MP3Frame, so MP3 data started
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// sizeof(MP3Frame) - 1 bytes ago.
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mMP3Offset = aStreamOffset
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+ (buffer - aBuffer)
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- (sizeof(MP3Frame) - 1);
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buffer++;
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// If the stream has a variable bitrate, the first frame has metadata
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// we need for duration estimation and seeking. Start buffering it so we
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// can parse it later.
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mFirstFrameEnd = mMP3Offset + frameLen;
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uint64_t currOffset = buffer - aBuffer + aStreamOffset;
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uint64_t copyLen = std::min(mFirstFrameEnd - currOffset,
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(uint64_t)(bufferEnd - buffer));
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mFirstFrame.Append((const char *)buffer, copyLen);
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buffer += copyLen;
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} else {
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// Nothing to see here. Move along.
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buffer++;
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}
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}
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*aOutBytesRead = buffer - aBuffer;
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if (mFirstFrameEnd > -1 && mFirstFrameEnd <= aStreamOffset + buffer - aBuffer) {
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// We have our whole first frame. Try to find a VBR header.
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mNumFrames = FindNumVBRFrames(mFirstFrame);
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mFirstFrameEnd = -1;
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}
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return NS_OK;
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}
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void MP3FrameParser::Parse(const char* aBuffer, uint32_t aLength, uint64_t aOffset)
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{
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MutexAutoLock mon(mLock);
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if (HasExactDuration()) {
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// We know the duration; nothing to do here.
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return;
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}
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const uint8_t* buffer = reinterpret_cast<const uint8_t*>(aBuffer);
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int32_t length = aLength;
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uint64_t offset = aOffset;
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// Got some data we have seen already. Skip forward to what we need.
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if (aOffset < mOffset) {
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buffer += mOffset - aOffset;
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length -= mOffset - aOffset;
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offset = mOffset;
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if (length <= 0) {
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return;
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}
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}
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// If there is a discontinuity in the input stream, reset the state of the
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// parsers so we don't get any partial headers.
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if (mOffset < aOffset) {
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if (!mID3Parser.IsParsed()) {
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// Only reset this if it hasn't finished yet.
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mID3Parser.Reset();
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}
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if (mFirstFrameEnd > -1) {
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NS_WARNING("Discontinuity in input while buffering first frame.");
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mFirstFrameEnd = -1;
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}
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mMP3Parser.Reset();
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}
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uint32_t bytesRead = 0;
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if (NS_FAILED(ParseBuffer(buffer,
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length,
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offset,
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&bytesRead))) {
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return;
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}
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MOZ_ASSERT(length <= (int)bytesRead, "All bytes should have been consumed");
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// Update next data offset
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mOffset = offset + bytesRead;
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// If we've parsed lots of data and we still have nothing, just give up.
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// We don't count ID3 headers towards the skipped bytes count, as MP3 files
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// can have massive ID3 sections.
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if (!mID3Parser.IsParsed() && mMP3Offset < 0 &&
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mOffset - mTotalID3Size > MAX_SKIPPED_BYTES) {
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mIsMP3 = NOT_MP3;
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}
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}
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int64_t MP3FrameParser::GetDuration()
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{
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MutexAutoLock mon(mLock);
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if (!ParsedHeaders() || !mSamplesPerSecond) {
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// Not a single frame decoded yet.
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return -1;
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}
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|
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();
|
|
}
|
|
|
|
}
|