AVC1与H264的差别
大家好,又见面了,我是全栈君,祝每个程序员都可以多学几门语言。
今天上网时偶尔发现这个在我脑海里疑惑的问题的答案。
H.264 Video Types
The following media subtypes are defined for H.264 video.
Subtype | FOURCC | Description |
---|---|---|
MEDIASUBTYPE_AVC1 | ‘AVC1’ | H.264 bitstream without start codes. |
MEDIASUBTYPE_H264 | ‘H264’ | H.264 bitstream with start codes. |
MEDIASUBTYPE_h264 | ‘h264’ | Equivalent to MEDIASUBTYPE_H264, with a different FOURCC. |
MEDIASUBTYPE_X264 | ‘X264’ | Equivalent to MEDIASUBTYPE_H264, with a different FOURCC. |
MEDIASUBTYPE_x264 | ‘x264’ | Equivalent to MEDIASUBTYPE_H264, with a different FOURCC. |
The main difference between these media types is the presence of startcodes in the bitstream. If the subtype is MEDIASUBTYPE_AVC1, thebitstream does not contain start codes.
H.264 Bitstream Without Start Codes
The MP4 container format stores H.264 data without start codes.Instead, each NALU is prefixed by a length field, which gives thelength of the NALU in bytes. The size of the length field can vary, butis typically 1, 2, or 4 bytes.
When start codes are not present in the bitstream, the following media type is used.
Major type | MEDIATYPE_Video |
---|---|
Subtype | MEDIASUBTYPE_AVC1 |
Format type | FORMAT_MPEG2Video |
The format block is an MPEG2VIDEOINFO structure. This structure should be filled in as follows:
- hdr: A VIDEOINFOHEADER2 structure that describes the bitstream. No color table is present after the BITMAPINFOHEADER portion of the structure, and biClrUsed must be zero.
- dwStartTimeCode: Not used. Set to zero.
- cbSequenceHeader: The length of the dwSequenceHeader array in bytes.
- dwProfile: Specifies the H.264 profile.
- dwLevel: Specifies the H.264 level.
- dwFlags: The number of bytes used for the length field that appears before each NALU. The length field indicates the size of the following NALU in bytes. For example, if dwFlags is 4, each NALU is preceded by a 4-byte length field. The valid values are 1, 2, and 4.
- dwSequenceHeader: A byte array that may contain sequence parameter set (SPS) and picture parameter set (PPS) NALUs.
The MP4 container might contain sequence parameter sets (SPS) orpicture parameter sets (PPS) as special NAL units in file headers or ina separate stream (distinct from the video stream). When the format isestablished, the media type can specify SPS and PPS NAL units in the dwSequenceHeader array. If cbSequenceHeader is greater than zero, dwSequenceHeaderis the start of a byte array containing SPS and PPS NALUs, delimited by2-byte length fields, all in network byte order (big-endian). It ispossible to have both SPS and PPS, only one of these types, or none.The actual type of each NALU can be determined by examining thenal_unit_type field of the NALU itself.
When this media type is used, each media sample starts at thebeginning of a NALU, and NAL units do not span samples. This enablesthe decoder to recover from data corruption or dropped samples.
发布者:全栈程序员栈长,转载请注明出处:https://javaforall.cn/118812.html原文链接:https://javaforall.cn
相关文章
- 金融服务领域的大数据:即时分析
- 影响大数据、机器学习和人工智能未来发展的8个因素
- 从0开始构建一个属于你自己的PHP框架
- 如何将Hadoop集成到工作流程中?这6个优秀实践必看
- SEO公司使用大数据优化其模型的5种方法
- 关于Web Workers你需要了解的七件事
- 深入理解HTTPS原理、过程与实践
- 增强分析:数据和分析的未来
- PHP协程实现过程详解
- AI专家:大数据知识图谱——实战经验总结
- 关于PHP的错误机制总结
- 利用数据分析量化协同过滤算法的两大常见难题
- 怎么做大数据工作流调度系统?大厂架构师一语点破!
- 2019大数据处理必备的十大工具,从Linux到架构师必修
- OpenCV中的KMeans算法介绍与应用
- 教大家如果搭建一套phpstorm+wamp+xdebug调试PHP的环境
- CentOS下三种PHP拓展安装方法
- Go语言HTTP Server源码分析
- Go语言HTTP Server源码分析
- 2017年4月编程语言排行榜:Hack首次进入前五十