mirror of
https://github.com/axiomatic-systems/Bento4.git
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316 lines
9.8 KiB
C++
316 lines
9.8 KiB
C++
/*****************************************************************
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| AP4 - AAC ADTS Parser
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| Copyright 2002-2008 Axiomatic Systems, LLC
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| This file is part of Bento4/AP4 (MP4 Atom Processing Library).
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| Unless you have obtained Bento4 under a difference license,
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| this version of Bento4 is Bento4|GPL.
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| Bento4|GPL is free software; you can redistribute it and/or modify
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| it under the terms of the GNU General Public License as published by
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| the Free Software Foundation; either version 2, or (at your option)
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| any later version.
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| Bento4|GPL is distributed in the hope that it will be useful,
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| but WITHOUT ANY WARRANTY; without even the implied warranty of
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| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| GNU General Public License for more details.
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| You should have received a copy of the GNU General Public License
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| along with Bento4|GPL; see the file COPYING. If not, write to the
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| Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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| 02111-1307, USA.
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****************************************************************/
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/*----------------------------------------------------------------------
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| includes
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+---------------------------------------------------------------------*/
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#include "Ap4BitStream.h"
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#include "Ap4AdtsParser.h"
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/*----------------------------------------------------------------------
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| constants
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+---------------------------------------------------------------------*/
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#define AP4_ADTS_HEADER_SIZE 7
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#define AP4_ADTS_SYNC_MASK 0xFFF6 /* 12 sync bits plus 2 layer bits */
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#define AP4_ADTS_SYNC_PATTERN 0xFFF0 /* 12 sync bits=1 layer=0 */
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const AP4_UI32
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AP4_AdtsSamplingFrequencyTable[16] =
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{
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96000,
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88200,
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64000,
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48000,
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44100,
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32000,
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24000,
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22050,
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16000,
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12000,
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11025,
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8000,
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7350,
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0, /* Reserved */
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0, /* Reserved */
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0 /* Escape code */
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};
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/*----------------------------------------------------------------------+
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| AP4_AdtsHeader::AP4_AdtsHeader
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+----------------------------------------------------------------------*/
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AP4_AdtsHeader::AP4_AdtsHeader(const AP4_UI08* bytes)
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{
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// fixed part
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m_Id = ( bytes[1] & 0x08) >> 3;
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m_ProtectionAbsent = bytes[1] & 0x01;
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m_ProfileObjectType = ( bytes[2] & 0xC0) >> 6;
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m_SamplingFrequencyIndex = ( bytes[2] & 0x3C) >> 2;
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m_ChannelConfiguration = ((bytes[2] & 0x01) << 2) |
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((bytes[3] & 0xC0) >> 6);
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// variable part
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m_FrameLength = ((unsigned int)(bytes[3] & 0x03) << 11) |
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((unsigned int)(bytes[4] ) << 3) |
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((unsigned int)(bytes[5] & 0xE0) >> 5);
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m_RawDataBlocks = bytes[6] & 0x03;
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsHeader::MatchFixed
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| Check that two fixed headers are the same
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+----------------------------------------------------------------------*/
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bool
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AP4_AdtsHeader::MatchFixed(unsigned char* a, unsigned char* b)
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{
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if (a[0] == b[0] &&
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a[1] == b[1] &&
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a[2] == b[2] &&
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(a[3] & 0xF0) == (b[3] & 0xF0)) {
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return true;
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} else {
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return false;
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}
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsHeader::Check
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+----------------------------------------------------------------------*/
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AP4_Result
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AP4_AdtsHeader::Check()
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{
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// check that the sampling frequency index is valid
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if (m_SamplingFrequencyIndex >= 0xD) {
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return AP4_FAILURE;
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}
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/* MPEG2 does not use all profiles */
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if (m_Id == 1 && m_ProfileObjectType == 3) {
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return AP4_FAILURE;
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}
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return AP4_SUCCESS;
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::AP4_AdtsParser
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+----------------------------------------------------------------------*/
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AP4_AdtsParser::AP4_AdtsParser() :
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m_FrameCount(0)
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{
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::~AP4_AdtsParser
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+----------------------------------------------------------------------*/
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AP4_AdtsParser::~AP4_AdtsParser()
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{
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::Reset
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+----------------------------------------------------------------------*/
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AP4_Result
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AP4_AdtsParser::Reset()
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{
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m_FrameCount = 0;
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return AP4_SUCCESS;
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::Feed
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+----------------------------------------------------------------------*/
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AP4_Result
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AP4_AdtsParser::Feed(const AP4_UI08* buffer,
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AP4_Size* buffer_size,
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AP4_Flags flags)
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{
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AP4_Size free_space;
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/* update flags */
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m_Bits.m_Flags = flags;
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/* possible shortcut */
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if (buffer == NULL ||
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buffer_size == NULL ||
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*buffer_size == 0) {
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return AP4_SUCCESS;
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}
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/* see how much data we can write */
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free_space = m_Bits.GetBytesFree();
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if (*buffer_size > free_space) *buffer_size = free_space;
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if (*buffer_size == 0) return AP4_SUCCESS;
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/* write the data */
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return m_Bits.WriteBytes(buffer, *buffer_size);
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::FindHeader
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+----------------------------------------------------------------------*/
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AP4_Result
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AP4_AdtsParser::FindHeader(AP4_UI08* header)
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{
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AP4_Size available = m_Bits.GetBytesAvailable();
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/* look for the sync pattern */
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while (available-- >= AP4_ADTS_HEADER_SIZE) {
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m_Bits.PeekBytes(header, 2);
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if ((((header[0] << 8) | header[1]) & AP4_ADTS_SYNC_MASK) == AP4_ADTS_SYNC_PATTERN) {
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/* found a sync pattern, read the entire the header */
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m_Bits.PeekBytes(header, AP4_ADTS_HEADER_SIZE);
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return AP4_SUCCESS;
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} else {
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m_Bits.ReadByte(); // skip
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}
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}
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return AP4_ERROR_NOT_ENOUGH_DATA;
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::FindFrame
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+----------------------------------------------------------------------*/
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AP4_Result
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AP4_AdtsParser::FindFrame(AP4_AacFrame& frame)
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{
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unsigned int available;
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unsigned char raw_header[AP4_ADTS_HEADER_SIZE];
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AP4_Result result;
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/* align to the start of the next byte */
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m_Bits.ByteAlign();
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/* find a frame header */
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result = FindHeader(raw_header);
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if (AP4_FAILED(result)) return result;
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/* parse the header */
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AP4_AdtsHeader adts_header(raw_header);
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/* check the header */
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result = adts_header.Check();
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if (AP4_FAILED(result)) goto fail;
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/* check if we have enough data to peek at the next header */
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available = m_Bits.GetBytesAvailable();
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if (available >= adts_header.m_FrameLength+AP4_ADTS_HEADER_SIZE) {
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// enough to peek at the header of the next frame
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unsigned char peek_raw_header[AP4_ADTS_HEADER_SIZE];
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m_Bits.SkipBytes(adts_header.m_FrameLength);
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m_Bits.PeekBytes(peek_raw_header, AP4_ADTS_HEADER_SIZE);
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m_Bits.SkipBytes(-((int)adts_header.m_FrameLength));
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/* check the header */
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AP4_AdtsHeader peek_adts_header(peek_raw_header);
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result = peek_adts_header.Check();
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if (AP4_FAILED(result)) goto fail;
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/* check that the fixed part of this header is the same as the */
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/* fixed part of the previous header */
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if (!AP4_AdtsHeader::MatchFixed(peek_raw_header, raw_header)) {
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goto fail;
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}
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} else if (available < adts_header.m_FrameLength || (m_Bits.m_Flags & AP4_BITSTREAM_FLAG_EOS) == 0) {
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// not enough for a frame, or not at the end (in which case we'll want to peek at the next header)
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return AP4_ERROR_NOT_ENOUGH_DATA;
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}
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m_Bits.SkipBytes(AP4_ADTS_HEADER_SIZE);
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/* fill in the frame info */
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frame.m_Info.m_Standard = (adts_header.m_Id == 1 ?
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AP4_AAC_STANDARD_MPEG2 :
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AP4_AAC_STANDARD_MPEG4);
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switch (adts_header.m_ProfileObjectType) {
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case 0:
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frame.m_Info.m_Profile = AP4_AAC_PROFILE_MAIN;
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break;
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case 1:
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frame.m_Info.m_Profile = AP4_AAC_PROFILE_LC;
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break;
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case 2:
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frame.m_Info.m_Profile = AP4_AAC_PROFILE_SSR;
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break;
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case 3:
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frame.m_Info.m_Profile = AP4_AAC_PROFILE_LTP;
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}
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frame.m_Info.m_FrameLength = adts_header.m_FrameLength-AP4_ADTS_HEADER_SIZE;
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frame.m_Info.m_ChannelConfiguration = adts_header.m_ChannelConfiguration;
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frame.m_Info.m_SamplingFrequencyIndex = adts_header.m_SamplingFrequencyIndex;
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frame.m_Info.m_SamplingFrequency = AP4_AdtsSamplingFrequencyTable[adts_header.m_SamplingFrequencyIndex];
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/* skip crc if present */
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if (adts_header.m_ProtectionAbsent == 0) {
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m_Bits.SkipBits(16);
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}
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/* set the frame source */
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frame.m_Source = &m_Bits;
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return AP4_SUCCESS;
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fail:
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/* skip the header and return (only skip the first byte in */
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/* case this was a false header that hides one just after) */
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//m_Bits.SkipBytes(-(AP4_ADTS_HEADER_SIZE-1));
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return AP4_ERROR_CORRUPTED_BITSTREAM;
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::GetBytesFree
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+----------------------------------------------------------------------*/
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AP4_Size
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AP4_AdtsParser::GetBytesFree()
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{
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return (m_Bits.GetBytesFree());
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}
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/*----------------------------------------------------------------------+
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| AP4_AdtsParser::GetBytesAvailable
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+----------------------------------------------------------------------*/
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AP4_Size
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AP4_AdtsParser::GetBytesAvailable()
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{
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return (m_Bits.GetBytesAvailable());
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}
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