live555源码分析----H264的数据处理

Boolean?H264VideoRTPSink::continuePlaying()?{??
1. ??//?First,?check?whether?we?have?a?'fragmenter'?class?set?up?yet.??
2. //?If?not,?create?it?now:??
3. if?(fOurFragmenter?==?NULL)?{??
4. //创建一个辅助类H264FUAFragmenter，用于H264按照RFC3984进行RTP打包??
5. ????fOurFragmenter?=?new?H264FUAFragmenter(envir(),?fSource,?OutPacketBuffer::maxSize,??
6. ???????????????????????ourMaxPacketSize()?-?12/*RTP?hdr?size*/);??
7. ????fSource?=?fOurFragmenter;??
8. ??}??
9. //?Then?call?the?parent?class's?implementation:??
10. return?MultiFramedRTPSink::continuePlaying();??
11. }??

void?FramedSource::getNextFrame(unsigned?char*?to,?unsigned?maxSize,255); background-color:inherit">????????????????afterGettingFunc*?afterGettingFunc,??
1. ????????????????void*?afterGettingClientData,255); background-color:inherit">????????????????onCloseFunc*?onCloseFunc,0); background-color:inherit; font-weight:bold">void*?onCloseClientData)?{??
2. //?Make?sure?we're?not?already?being?read:??
3. if?(fIsCurrentlyAwaitingData)?{??
4. ????envir()?<<?"FramedSource["?<<?this?<<?"]::getNextFrame():?attempting?to?read?more?than?once?at?the?same?time!n";??
5. ????envir().internalError();??
6. ??fTo?=?to;?????????????//buffer地址??
7. ??fMaxSize?=?maxSize;???//buffer最大长度??
8. ??fNumTruncatedBytes?=?0;?//?by?default;?could?be?changed?by?doGetNextFrame()??
9. ??fDurationInMicroseconds?=?0;?//?by?default;?could?be?changed?by?doGetNextFrame()??
10. ??fAfterGettingFunc?=?afterGettingFunc;?????????????//获取完一个frame后将执行这个函数??
11. ??fAfterGettingClientData?=?afterGettingClientData;?//这个参数就是MultiFramedRTPSink类型指针??
12. ??fOnCloseFunc?=?onCloseFunc;??
13. ??fOnCloseClientData?=?onCloseClientData;??
14. ??fIsCurrentlyAwaitingData?=?True;??
15. ??doGetNextFrame();??
16. }??

void?H264FUAFragmenter::doGetNextFrame()?{??
1. if?(fNumValidDataBytes?==?1)?{??
2. ??????//读取一个新的frame??
3. //?We?have?no?NAL?unit?data?currently?in?the?buffer.??Read?a?new?one:??
4. ????fInputSource->getNextFrame(&fInputBuffer[1],?fInputBufferSize?-?1,255); background-color:inherit">???????????????????afterGettingFrame,??
5. ???????????????????FramedSource::handleClosure,0); background-color:inherit; font-weight:bold">this);??
6. //??
7. //现在buffer中已经存在NALU数据了，需要考虑三种情况??
8. //1.一个新的NALU,且足够小能投递给RTP?sink。??
9. //2.一个新的NALU,但是比RTP?sink要求的包大了，投递第一个分片作为一个FU-A?packet,?并带上一个额外的头字节。??
10. //3.部分NALU数据,投递下一个分片作为一个FU-A?packet，并带上2个额外的头字节。??
11. //?We?have?NAL?unit?data?in?the?buffer.??There?are?three?cases?to?consider:??
12. //?1.?There?is?a?new?NAL?unit?in?the?buffer,?and?it's?small?enough?to?deliver??
13. //????to?the?RTP?sink?(as?is).??
14. //?2.?There?is?a?new?NAL?unit?in?the?buffer,?but?it's?too?large?to?deliver?to??
15. //????the?RTP?sink?in?its?entirety.??Deliver?the?first?fragment?of?this?data,??
16. //????as?a?FU-A?packet,?with?one?extra?preceding?header?byte.??
17. //?3.?There?is?a?NAL?unit?in?the?buffer,?and?we've?already?delivered?some??
18. //????fragment(s)?of?this.??Deliver?the?next?fragment?of?this?data,??
19. ??
20. ????if?(fMaxSize?<?fMaxOutputPacketSize)?{?//?shouldn't?happen??
21. ??????envir()?<<?"H264FUAFragmenter::doGetNextFrame():?fMaxSize?("??
22. ??????????<<?fMaxSize?<<?")?is?smaller?than?expectedn";??
23. ????}???????fMaxSize?=?fMaxOutputPacketSize;??
24. ????}??
25. ????fLastFragmentCompletedNALUnit?=?True;?//?by?default??
26. if?(fCurDataOffset?==?1)?{?//?case?1?or?2??
27. ??????if?(fNumValidDataBytes?-?1?<=?fMaxSize)?{?//?case?1??
28. ??????????//情况1,?处理整个NALU??
29. ????memmove(fTo,?&fInputBuffer[1],?fNumValidDataBytes?-?1);??
30. ????fFrameSize?=?fNumValidDataBytes?-?1;??
31. ????fCurDataOffset?=?fNumValidDataBytes;??
32. ??????}?else?{?//?case?2??
33. //情况2，处理NALU的第1个分片。注意，我们添加FU指示符和FU头字节(with?S?bit)到包的最前面(??
34. //重用已经存在的NAL?头字节作为FU的头字节)??
35. //?We?need?to?send?the?NAL?unit?data?as?FU-A?packets.??Deliver?the?first??
36. //?packet?now.??Note?that?we?add?FU?indicator?and?FU?header?bytes?to?the?front??
37. //?of?the?packet?(reusing?the?existing?NAL?header?byte?for?the?FU?header).??
38. ????fInputBuffer[0]?=?(fInputBuffer[1]?&?0xE0)?|?28;?//?FU?indicator??
39. ????fInputBuffer[1]?=?0x80?|?(fInputBuffer[1]?&?0x1F);?//?FU?header?(with?S?bit)???重用NALU头字节??
40. ????fFrameSize?=?fMaxSize;??
41. ????fCurDataOffset?+=?fMaxSize?-?1;??
42. ????fLastFragmentCompletedNALUnit?=?False;??
43. ??????}??
44. //?case?3??
45. ????????//情况3，处理非第1个分片。需要添加FU指示符和FU头(我们重用了第一个分片中的字节，但是需要清除S位，??
46. //并在最后一个分片中添加E位)??
47. //?We?are?sending?this?NAL?unit?data?as?FU-A?packets.??We've?already?sent?the??
48. //?first?packet?(fragment).??Now,?send?the?next?fragment.??Note?that?we?add??
49. //?FU?indicator?and?FU?header?bytes?to?the?front.??(We?reuse?these?bytes?that??
50. //?we?already?sent?for?the?first?fragment,?but?clear?the?S?bit,?and?add?the?E??
51. //?bit?if?this?is?the?last?fragment.)??
52. ??????fInputBuffer[fCurDataOffset-2]?=?fInputBuffer[0];???????fInputBuffer[fCurDataOffset-1]?=?fInputBuffer[1]&~0x80;?//?FU?header?(no?S?bit)??
53. ??????unsigned?numBytesToSend?=?2?+?fNumValidDataBytes?-?fCurDataOffset;??
54. if?(numBytesToSend?>?fMaxSize)?{??
55. //?We?can't?send?all?of?the?remaining?data?this?time:??
56. ????numBytesToSend?=?fMaxSize;??
57. ????fLastFragmentCompletedNALUnit?=?False;??
58. else?{??
59. //最后一个分片，需要在FU头中设置E标志位??
60. //?This?is?the?last?fragment:??
61. ????fInputBuffer[fCurDataOffset-1]?|=?0x40;?//?set?the?E?bit?in?the?FU?header??
62. ????fNumTruncatedBytes?=?fSaveNumTruncatedBytes;??
63. ??????}??
64. ??????memmove(fTo,?&fInputBuffer[fCurDataOffset-2],?numBytesToSend);??
65. ??????fFrameSize?=?numBytesToSend;??
66. ??????fCurDataOffset?+=?numBytesToSend?-?2;??
67. ????}??
68. if?(fCurDataOffset?>=?fNumValidDataBytes)?{??
69. //?We're?done?with?this?data.??Reset?the?pointers?for?receiving?new?data:??
70. ??????fNumValidDataBytes?=?fCurDataOffset?=?1;??
71. //?Complete?delivery?to?the?client:??
72. ????FramedSource::afterGetting(}??

void?H264FUAFragmenter::afterGettingFrame(void*?clientData,?unsigned?frameSize,255); background-color:inherit">??????????????????????unsigned?numTruncatedBytes,255); background-color:inherit">??????????????????????struct?timeval?presentationTime,255); background-color:inherit">??????????????????????unsigned?durationInMicroseconds)?{??
1. ??H264FUAFragmenter*?fragmenter?=?(H264FUAFragmenter*)clientData;??
2. ??fragmenter->afterGettingFrame1(frameSize,?numTruncatedBytes,?presentationTime,255); background-color:inherit">?????????????????durationInMicroseconds);??
3. }??

void?H264FUAFragmenter::afterGettingFrame1(unsigned?frameSize,255); background-color:inherit">???????????????????????unsigned?numTruncatedBytes,255); background-color:inherit">??????????????????????????????????????????????unsigned?durationInMicroseconds)?{??
1. ??fNumValidDataBytes?+=?frameSize;??????//保存读到的frame长度??
2. ??fSaveNumTruncatedBytes?=?numTruncatedBytes;??
3. ??fPresentationTime?=?presentationTime;??
4. ??fDurationInMicroseconds?=?durationInMicroseconds;??
5. //?Deliver?data?to?the?client:??
6. }??

?? ?H264FUAFragmenter::doGetNextFrame函数中第二个条件分支中，处理H264的RTP分片问题，这里是按照RFC3984进行RTP封装的。你应该注意到，在上篇文章"RTP的打包与发送"中，也出现了分片的代码(MultiFramedRTPSink::packFrame函数中)，那里直接将frame按MTU的长度来拆分。那为什么H264还要自定义一套RTP打包的标准呢？暂时我也不清楚。

void?FramedSource::afterGetting(FramedSource*?source)?{??
1. ??source->fIsCurrentlyAwaitingData?=?False;?????//表示已经获取到数据了，处于非等待状态??
2. //?indicates?that?we?can?be?read?again??
3. //?Note?that?this?needs?to?be?done?here,?in?case?the?"fAfterFunc"??
4. //?called?below?tries?to?read?another?frame?(which?it?usually?will)??
5. //通过回调用进行后续处理??
6. if?(source->fAfterGettingFunc?!=?NULL)?{??
7. ????(*(source->fAfterGettingFunc))(source->fAfterGettingClientData,255); background-color:inherit">???????????????????source->fFrameSize,?source->fNumTruncatedBytes,255); background-color:inherit">???????????????????source->fPresentationTime,255); background-color:inherit">???????????????????source->fDurationInMicroseconds);??
8. }??

void?MPEGVideoStreamFramer::doGetNextFrame()?{??
1. ??fParser->registerReadInterest(fTo,?fMaxSize);?//将目的buffer信息注册到语法分析类中??
2. ??continueReadProcessing();?????//继续进行读数据??
3. }??

void?MPEGVideoStreamFramer::continueReadProcessing()?{??
1. ??unsigned?acquiredFrameSize?=?fParser->parse();????//文件的语法分析(即demux)??
2. if?(acquiredFrameSize?>?0)?{??
3. //?We?were?able?to?acquire?a?frame?from?the?input.??
4. //?It?has?already?been?copied?to?the?reader's?space.??
5. ????fFrameSize?=?acquiredFrameSize;??
6. ????fNumTruncatedBytes?=?fParser->numTruncatedBytes();??
7. //?"fPresentationTime"?should?have?already?been?computed.??
8. //?Compute?"fDurationInMicroseconds"?now:??
9. ????fDurationInMicroseconds??
10. ??????=?(fFrameRate?==?0.0?||?((int)fPictureCount)?<?0)???0??
11. ??????:?(unsigned)((fPictureCount*1000000)/fFrameRate);??
12. #ifdef?DEBUG??
13. ????fprintf(stderr,?"%d?bytes?@%u.%06d,?fDurationInMicroseconds:?%d?((%d*1000000)/%f)n",?acquiredFrameSize,?fPresentationTime.tv_sec,?fPresentationTime.tv_usec,?fDurationInMicroseconds,?fPictureCount,?fFrameRate);??
14. #endif??
15. ????fPictureCount?=?0;??
16. ??????
17. //调用自身的afterGetting函数，因为这不一个"leaf"?source,?所以可能直接调用，??
18. //而不用担心出现无限递归??
19. //?Call?our?own?'after?getting'?function.??Because?we're?not?a?'leaf'??
20. //?source,?we?can?call?this?directly,?without?risking?infinite?recursion.??
21. ????afterGetting(//?We?were?unable?to?parse?a?complete?frame?from?the?input,?because:??
22. //?-?we?had?to?read?more?data?from?the?source?stream,?or??
23. //?-?the?source?stream?has?ended.??
24. }??

unsigned?H264VideoStreamParser::parse()?{??
1. try?{??
2. //首先找到起始符号,?并跳过。文件流的最开始必需以0x00000001开始，但后续的NALU充许以0x000001(3?bytes)作为分隔??
3. //?The?stream?must?start?with?a?0x00000001:??
4. if?(!fHaveSeenFirstStartCode)?{??
5. //?Skip?over?any?input?bytes?that?precede?the?first?0x00000001:??
6. ??????u_int32_t?first4Bytes;??
7. while?((first4Bytes?=?test4Bytes())?!=?0x00000001)?{??
8. ????get1Byte();?setParseState();?//?ensures?that?we?progress?over?bad?data??
9. ??????skipBytes(4);?//?skip?this?initial?code??
10. ????????
11. ??????setParseState();??
12. ??????fHaveSeenFirstStartCode?=?True;?//?from?now?on??
13. //将起始标志也保存到目的缓冲区中??
14. if?(fOutputStartCodeSize?>?0)?{??
15. //?Include?a?start?code?in?the?output:??
16. ??????save4Bytes(0x00000001);?????
17. //保存所有数据，直至遇到起始标志，或者文件结束符。需要注意NALU中的第一个字节，因为它指示了NALU的类型??
18. //?Then?save?everything?up?until?the?next?0x00000001?(4?bytes)?or?0x000001?(3?bytes),?or?we?hit?EOF.??
19. //?Also?make?note?of?the?first?byte,?because?it?contains?the?"nal_unit_type":???
20. ????u_int8_t?firstByte;??
21. if?(haveSeenEOF())?{??
22. ???????//已经设置了文件结束标志，将剩下的数据保存也来即可??
23. //?We?hit?EOF?the?last?time?that?we?tried?to?parse?this?data,204); background-color:inherit">//?so?we?know?that?the?remaining?unparsed?data?forms?a?complete?NAL?unit:??
24. ??????unsigned?remainingDataSize?=?totNumValidBytes()?-?curOffset();??
25. if?(remainingDataSize?==?0)?(void)get1Byte();?//?forces?another?read,?which?will?cause?EOF?to?get?handled?for?real?this?time??
26. #ifdef?DEBUG??
27. ??????fprintf(stderr,0); background-color:inherit">"This?NAL?unit?(%d?bytes)?ends?with?EOFn",?remainingDataSize);??
28. #endif??
29. if?(remainingDataSize?==?0)?return?0;??
30. ??????firstByte?=?get1Byte();???//将第一个字节保存下来，其指示了NALU的类型??
31. ??????saveByte(firstByte);??
32. while?(--remainingDataSize?>?0)?{??
33. ????saveByte(get1Byte());??
34. ??????u_int32_t?next4Bytes?=?test4Bytes();??
35. ??????firstByte?=?next4Bytes>>24;???//将第一个字节保存下来??
36. //将下一个起始符号之前的数据都保存下来??
37. while?(next4Bytes?!=?0x00000001?&&?(next4Bytes&0xFFFFFF00)?!=?0x00000100)?{??
38. //?We?save?at?least?some?of?"next4Bytes".??
39. if?((unsigned)(next4Bytes&0xFF)?>?1)?{??//一次可以保存4个字节,并不需要一个一个字节对比，除非到了结尾??
40. //?Common?case:?0x00000001?or?0x000001?definitely?doesn't?begin?anywhere?in?"next4Bytes",?so?we?save?all?of?it:??
41. ??????save4Bytes(next4Bytes);??
42. ??????skipBytes(4);??
43. //?Save?the?first?byte,?and?continue?testing?the?rest:??
44. ??????saveByte(next4Bytes>>24);??
45. ??????skipBytes(1);??
46. ????next4Bytes?=?test4Bytes();??
47. //?Assert:?next4Bytes?starts?with?0x00000001?or?0x000001,?and?we've?saved?all?previous?bytes?(forming?a?complete?NAL?unit).??
48. //?Skip?over?these?remaining?bytes,?up?until?the?start?of?the?next?NAL?unit:??
49. if?(next4Bytes?==?0x00000001)?{??
50. ????skipBytes(4);??
51. ????skipBytes(3);??
52. ???
53. ????u_int8_t?nal_ref_idc?=?(firstByte&0x60)>>5;??
54. ????u_int8_t?nal_unit_type?=?firstByte&0x1F;??
55. "Parsed?%d-byte?NAL-unit?(nal_ref_idc:?%d,?nal_unit_type:?%d?("%s"))n",255); background-color:inherit">????????curFrameSize()-fOutputStartCodeSize,?nal_ref_idc,?nal_unit_type,?nal_unit_type_description[nal_unit_type]);??
56. //下面根据NALU的类型来作具体的分析??
57. switch?(nal_unit_type)?{??
58. case?6:?{?//?Supplemental?enhancement?information?(SEI)??
59. ????analyze_sei_data();??
60. //?Later,?perhaps?adjust?"fPresentationTime"?if?we?saw?a?"pic_timing"?SEI?payload????#####??
61. break;??
62. case?7:?{?//?Sequence?parameter?set?(序列参数集)??
63. //保存一份SPS的副本到H264VideoStreamFramer中，后面的pps也需要保存，sps中可能还包含了帧率信息??
64. ??
65. ????usingSource()->saveCopyOfSPS(fStartOfFrame?+?fOutputStartCodeSize,?fTo?-?fStartOfFrame?-?fOutputStartCodeSize);??
66. //?Parse?this?NAL?unit?to?check?whether?frame?rate?information?is?present:??
67. ????unsigned?num_units_in_tick,?time_scale,?fixed_frame_rate_flag;??
68. ????analyze_seq_parameter_set_data(num_units_in_tick,?fixed_frame_rate_flag);??
69. if?(time_scale?>?0?&&?num_units_in_tick?>?0)?{??
70. ??????usingSource()->fFrameRate?=?time_scale/(2.0*num_units_in_tick);???//sps中包含了帧率信息??
71. "Set?frame?rate?to?%f?fpsn",?usingSource()->fFrameRate);??
72. if?(fixed_frame_rate_flag?==?0)?{??
73. ????????fprintf(stderr,0); background-color:inherit">"tWARNING:?"fixed_frame_rate_flag"?was?not?setn");??
74. else?{????//sps中不包含帧率信息，则使用source中设置的默认帧率??
75. "tThis?"Sequence?Parameter?Set"?NAL?unit?contained?no?frame?rate?information,?so?we?use?a?default?frame?rate?of?%f?fpsn",?usingSource()->fFrameRate);??
76. case?8:?{?//?Picture?parameter?set?(图像参数集PPS)??
77. //?Save?a?copy?of?this?NAL?unit,?in?case?the?downstream?object?wants?to?see?it:??
78. ????usingSource()->saveCopyOfPPS(fStartOfFrame?+?fOutputStartCodeSize,?fTo?-?fStartOfFrame?-?fOutputStartCodeSize);??
79. ??????
80. ????usingSource()->setPresentationTime();???//设置当前的时间??
81. ????unsigned?long?secs?=?(unsigned?long)usingSource()->fPresentationTime.tv_sec;??
82. ????unsigned?uSecs?=?(unsigned)usingSource()->fPresentationTime.tv_usec;??
83. "tPresentation?time:?%lu.%06un",?secs,?uSecs);??
84. //如果这个NALU是一个VCL?NALU(即包含的是视频数据)，我们需要扫描下一个NALU的起始符，??
85. //以判断这个NALU是否是当前的"access?unit"(这个"access?unit"应该可以理解为一帧图像帧吧)。??
86. //我们需要根据这个信息去指明何时该增加"fPresentationTime"(RTP?打包时也需要根据这个信息，决定是否设置"M"位)。??
87. //?If?this?NAL?unit?is?a?VCL?NAL?unit,?we?also?scan?the?start?of?the?next?NAL?unit,?to?determine?whether?this?NAL?unit??
88. //?ends?the?current?'access?unit'.??We?need?this?information?to?figure?out?when?to?increment?"fPresentationTime".??
89. //?(RTP?streamers?also?need?to?know?this?in?order?to?figure?out?whether?or?not?to?set?the?"M"?bit.)??
90. ????Boolean?thisNALUnitEndsAccessUnit?=?False;?//?until?we?learn?otherwise???
91. if?(haveSeenEOF())?{??
92. //?There?is?no?next?NAL?unit,?so?we?assume?that?this?one?ends?the?current?'access?unit':??
93. ??????thisNALUnitEndsAccessUnit?=?True;??
94. ??????Boolean?const?isVCL?=?nal_unit_type?<=?5?&&?nal_unit_type?>?0;?//?Would?need?to?include?type?20?for?SVC?and?MVC?#####??
95. if?(isVCL)?{??
96. ????u_int32_t?first4BytesOfNextNALUnit?=?test4Bytes();??
97. ????u_int8_t?firstByteOfNextNALUnit?=?first4BytesOfNextNALUnit>>24;??
98. ????u_int8_t?next_nal_ref_idc?=?(firstByteOfNextNALUnit&0x60)>>5;??
99. ????u_int8_t?next_nal_unit_type?=?firstByteOfNextNALUnit&0x1F;??
100. if?(next_nal_unit_type?>=?6)?{??
101. //下一个NALU不是VCL的，当前的"access?unit"结束了??
102. //?The?next?NAL?unit?is?not?a?VCL;?therefore,?we?assume?that?this?NAL?unit?ends?the?current?'access?unit':??
103. "t(The?next?NAL?unit?is?not?a?VCL)n");??
104. //下一个NALU也是VCL的，还需要检查一下它们是不是属于同一个"access?unit"??
105. //?The?next?NAL?unit?is?also?a?VLC.??We?need?to?examine?it?a?little?to?figure?out?if?it's?a?different?'access?unit'.??
106. //?(We?use?many?of?the?criteria?described?in?section?7.4.1.2.4?of?the?H.264?specification.)??
107. ??????Boolean?IdrPicFlag?=?nal_unit_type?==?5;??
108. ??????Boolean?next_IdrPicFlag?=?next_nal_unit_type?==?5;??
109. if?(next_IdrPicFlag?!=?IdrPicFlag)?{??
110. //?IdrPicFlag?differs?in?value??
111. "t(IdrPicFlag?differs?in?value)n");??
112. ????????thisNALUnitEndsAccessUnit?=?True;??
113. else?if?(next_nal_ref_idc?!=?nal_ref_idc?&&?next_nal_ref_idc*nal_ref_idc?==?0)?{??
114. //?nal_ref_idc?differs?in?value?with?one?of?the?nal_ref_idc?values?being?equal?to?0??
115. "t(nal_ref_idc?differs?in?value?with?one?of?the?nal_ref_idc?values?being?equal?to?0)n");??
116. if?((nal_unit_type?==?1?||?nal_unit_type?==?2?||?nal_unit_type?==?5)??
117. ?????????????&&?(next_nal_unit_type?==?1?||?next_nal_unit_type?==?2?||?next_nal_unit_type?==?5))?{??
118. //?Both?this?and?the?next?NAL?units?begin?with?a?"slice_header".??
119. //?Parse?this?(for?each),?to?get?parameters?that?we?can?compare:??
120. ??????????
121. //?Current?NAL?unit's?"slice_header":??
122. ????????unsigned?frame_num,?pic_parameter_set_id,?idr_pic_id;??
123. ????????Boolean?field_pic_flag,?bottom_field_flag;??
124. ????????analyze_slice_header(fStartOfFrame?+?fOutputStartCodeSize,?fTo,255); background-color:inherit">?????????????????frame_num,?idr_pic_id,?field_pic_flag,?bottom_field_flag);??
125. //?Next?NAL?unit's?"slice_header":??
126. "????Next?NAL?unit's?slice_header:n");??
127. ????????u_int8_t?next_slice_header[NUM_NEXT_SLICE_HEADER_BYTES_TO_ANALYZE];??
128. ????????testBytes(next_slice_header,0); background-color:inherit; font-weight:bold">sizeof?next_slice_header);??
129. ????????unsigned?next_frame_num,?next_pic_parameter_set_id,?next_idr_pic_id;??
130. ????????Boolean?next_field_pic_flag,?next_bottom_field_flag;??
131. ????????analyze_slice_header(next_slice_header,?&next_slice_header[sizeof?next_slice_header],?next_nal_unit_type,255); background-color:inherit">?????????????????next_frame_num,?next_idr_pic_id,?next_field_pic_flag,?next_bottom_field_flag);??
132. ??????????
133. ????????if?(next_frame_num?!=?frame_num)?{??
134. //?frame_num?differs?in?value??
135. ??????????fprintf(stderr,0); background-color:inherit">"t(frame_num?differs?in?value)n");??
136. ??????????thisNALUnitEndsAccessUnit?=?True;??
137. ????????}?if?(next_pic_parameter_set_id?!=?pic_parameter_set_id)?{??
138. //?pic_parameter_set_id?differs?in?value??
139. "t(pic_parameter_set_id?differs?in?value)n");??
140. if?(next_field_pic_flag?!=?field_pic_flag)?{??
141. //?field_pic_flag?differs?in?value??
142. "t(field_pic_flag?differs?in?value)n");??
143. if?(next_bottom_field_flag?!=?bottom_field_flag)?{??
144. //?bottom_field_flag?differs?in?value??
145. "t(bottom_field_flag?differs?in?value)n");??
146. if?(next_IdrPicFlag?==?1?&&?next_idr_pic_id?!=?idr_pic_id)?{??
147. //?IdrPicFlag?is?equal?to?1?for?both?and?idr_pic_id?differs?in?value??
148. //?Note:?We?already?know?that?IdrPicFlag?is?the?same?for?both.??
149. "t(IdrPicFlag?is?equal?to?1?for?both?and?idr_pic_id?differs?in?value)n");??
150. ??????????thisNALUnitEndsAccessUnit?=?True;??
151. ????????}??
152. if?(thisNALUnitEndsAccessUnit)?{??
153. "*****This?NAL?unit?ends?the?current?access?unit*****n");??
154. ??????usingSource()->fPictureEndMarker?=?True;??//这里就是设置RTP打包时用到的M标志了??
155. ??????++usingSource()->fPictureCount;??
156. //下一个NALU不再属于当前"access　unit""时，才改变时间??
157. //?Note?that?the?presentation?time?for?the?next?NAL?unit?will?be?different:??
158. struct?timeval&?nextPT?=?usingSource()->fNextPresentationTime;?//?alias　这里是引用　??
159. ??????nextPT?=?usingSource()->fPresentationTime;??
160. ??????double?nextFraction?=?nextPT.tv_usec/1000000.0?+?1/usingSource()->fFrameRate;???
161. ??????unsigned?nextSecsIncrement?=?(long)nextFraction;??
162. ??????nextPT.tv_sec?+=?(long)nextSecsIncrement;??
163. ??????nextPT.tv_usec?=?(long)((nextFraction?-?nextSecsIncrement)*1000000);??
164. ????setParseState();??
165. return?curFrameSize();??
166. catch?(int?/*e*/)?{??
167. "H264VideoStreamParser::parse()?EXCEPTION?(This?is?normal?behavior?-?*not*?an?error)n");??
168. return?0;??//?the?parsing?got?interrupted??
169. }??

（编辑：李大同）

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