MP4

• https://www.cnblogs.com/chyingp/p/mp4-file-format.html
• https://lucius0.github.io/2018/01/16/archivers/media-study-08/
• ffmpeg\libavformat\movenc.c

• 参考：https://www.cnblogs.com/codertian/p/8277965.html
• 文档下载：https://standards.iso.org/ittf/PubliclyAvailableStandards/index.html
• 14496-12 14496-14 14496-15 下载要收费了， csdn 解决
  • iso_iec_14496-12_2015.pdf
  • iso_iec_14496-14-2020.pdf
  • iso_iec_14496-15_2013_avcff.pdf
  • 标准iso-iec14496-15-2017.docx 这个是在WPS里用图片型PDF经ORC扫描生成的，可能有错漏。查看时可比对2013版
• 14496-15 涉及h264 h265 流 的 stsd box 封装
  • 14496-15-2017 5.4.2 讲述 h264 的 avc1-avcC box 结构， avcC 主要是 AVCDecoderConfigurationRecord, 这个见 5.3.3.1.2
  • avc1 是 AVCSampleEntry ， 继承 VisualSampleEntry
  • VisualSampleEntry 结构见 14496-12_2015 12.1.3.2

    	class VisualSampleEntry(codingname) extends SampleEntry (codingname){ 
    		 unsigned int(16) pre_defined = 0; 
    		 const unsigned int(16) reserved = 0; 
    		 unsigned int(32)[3] pre_defined = 0; 
    		 unsigned int(16) width; 
    		 unsigned int(16) height; 
    		 template unsigned int(32) horizresolution = 0x00480000; // 72 dpi 
    		 template unsigned int(32) vertresolution = 0x00480000; // 72 dpi 
    		 const unsigned int(32) reserved = 0; 
    		 template unsigned int(16) frame_count = 1; 
    		 string[32] compressorname; 
    		 template unsigned int(16) depth = 0x0018; 
    		 int(16) pre_defined = -1; 
    		 // other boxes from derived specifications 
    		 CleanApertureBox clap; // optional 
    		 PixelAspectRatioBox pasp; // optional 
    	}
     
    	aligned(8) abstract class SampleEntry (unsigned int(32) format) 
    	 extends Box(format){ 
    	 const unsigned int(8)[6] reserved = 0; 
    	 unsigned int(16) data_reference_index; 
    	}

• H265 的 hev1 - hvcC box 结构 14496-15_2013 就有提及，在 8.4.1 章节， hvcC box 包含 `HEVCDecoderConfigurationRecord` 结构，具体见 8.3.3.1 章节
• Compressorname in the base class VisualSampleEntry indicates the name of the compressor used with the value “\013HEVC Coding” being recommended (\013 is 11, the length of the string in

bytes).

• HEVCDecoderConfigurationRecord 结构：

  	aligned(8) class HEVCDecoderConfigurationRecord { 
  		 unsigned int(8) configurationVersion = 1; 
  		 unsigned int(2) general_profile_space; 
  		 unsigned int(1) general_tier_flag; 
  		 unsigned int(5) general_profile_idc; 
  		 unsigned int(32) general_profile_compatibility_flags; 
  		 unsigned int(48) general_constraint_indicator_flags; 
  		 unsigned int(8) general_level_idc; 
  		 bit(4) reserved = ‘1111’b; 
  		 unsigned int(12) min_spatial_segmentation_idc; 
  		 bit(6) reserved = ‘111111’b; 
  		 unsigned int(2) parallelismType; 
  		 bit(6) reserved = ‘111111’b; 
  		 unsigned int(2) chromaFormat; 
  		 bit(5) reserved = ‘11111’b; 
  		 unsigned int(3) bitDepthLumaMinus8; 
  		 bit(5) reserved = ‘11111’b; 
  		 unsigned int(3) bitDepthChromaMinus8; 
  		 bit(16) avgFrameRate; 
  		 bit(2) constantFrameRate; 
  		 bit(3) numTemporalLayers; 
  		 bit(1) temporalIdNested; 
  		 unsigned int(2) lengthSizeMinusOne; 
  		 unsigned int(8) numOfArrays; 
  		 for (j=0; j < numOfArrays; j++) { 
  			 bit(1) array_completeness; 
  			 unsigned int(1) reserved = 0; 
  			 unsigned int(6) NAL_unit_type; 
  			 unsigned int(16) numNalus; 
  			 for (i=0; i< numNalus; i++) { 
  				 unsigned int(16) nalUnitLength; 
  				 bit(8*nalUnitLength) nalUnit; 
  			 } 
  		 } 
  	}

• mp4 的主要box：
• 

• fmp4 的moov box:
• 

• 组装fmp4的 moov box 必须获取视频流的 width, height, pps, sps

• 获取 pps sps:
• avc1 参考 ffmpeg 的 mov_write_video_tag 函数

• https://www.cnblogs.com/wangguchangqing/p/6297792.html
• Golomb编码，及其两个变种：Golomb-Rice和Exp-Golomb