基本术语

DRM: Digital Rights Managment, 通过加密手段防止视频被非法播放

HLS: (HTTP Live Streaming). Based on HTTP, for Apple specific

HLS presentation consists of media segments that contain audio, video, subtitles, or a multiplex of both audio and video. Media segment URLs are referenced from media playlists (a text-based format, usually stored in files with the .m3u8 file extension).
Use MPEG2 TS(Transport Stream) format. Normally, we use MP4 format, to convert it to MPEG2 TS which can be played as Live streaming.
the media files may be encrypted

MPEG DASH Adaptive Streaming. Based on HTTP, for other browsers (except for apple)

an MPEG DASH presentation consists of an initial XML manfifest, called the Media Presentation Document (MPD for short), which describes media segments that form a complete presentation
tutorial: https://www.bento4.com/developers/dash/

RTMP (Real Time Messaging Protocol) cannot be used on webpage directly. Use to serve Flash

ffmpeg

crop videos:P downgrade resolution
- ffmpeg -i inputfile.avi -croptop 88 -cropbottom 88 -cropleft 360 -cropright 360 outputfile.avi
tutorial: http://keycorner.org/pub/text/doc/ffmpeg-tutorial.htm

Tools

mp4hls: mp4 to hls. Based on mp42hls. one or more MP4 files to a multi-bitrate HLS master playlist
- tutorial: https://www.bento4.com/developers/hls/
mp42hls: single MP4 file to single-bitrate HLS presentation
mp4dash: convert one or more input media files into a complete MPEG DASH presentation
- related tools:
  - mp4fragment: the input of mp4dash has to be fragmented first
  - mp4info: show whether an mp4 file is fragmented or not

直播推送协议比较

RTMP：

优点 CDN 支持良好，主流的 CDN 厂商都支持协议简单，在各平台上实现容易缺点基于 TCP ，传输成本高，在弱网环境丢包率高的情况下问题显著不支持浏览器推送 Adobe 私有协议，Adobe 已经不再更新
WebRTC

优点 W3C 标准，主流浏览器支持程度高 Google 在背后支撑，并在各平台有参考实现底层基于 SRTP 和 UDP，弱网情况优化空间大可以实现点对点通信，通信双方延时低缺点 ICE,STUN,TURN 传统 CDN 没有类似的服务提供

七牛云

Video

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