v3_EN_DeliveryMethod

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There are three major delivery methods for media streaming:

1. LIVE streaming: RTMP/HTTP-FLV/HTTP-TS/HTTP-MP3, directly write audio/video packets to client over TCP.
2. LIVE pseudo streaming: HLS/HDS/DASH, transmux RTMP to pieces of segment file, delivery over HTTP.
3. VOD: DVR RTMP to VOD file.

RTMP PK HTTP

The two major delivery methods on internet, HLS and RTMP.

Ignore other delivery protocol, which is not used on internet:

• UDP: Private protocols, realtime protocol, latence in ms.
• P2P: FlashP2P of Adobe, others are private protocol. Large latence, in minutes.
• RTSP: Private protocol not for internet.

And the protocol base on HTTP:

• HTTP progressive: Ancient protocol, not used now.
• HTTP stream: Support seek in query string, for instance, http://x/x.mp4?start=x.
• HLS: The HLS is developed by Apple. Both Apple and Android support it.
• HDS: The HLS like developed by Adobe, shit.
• DASH: The HLS like developed by some companies, not used in China.

Compare the delivery methods on internet:

• HLS: Apple HLS, for both live and vod.
• HTTP: HTTP stream, private http stream, for vod.
• RTMP: Adobe RTMP, for live stream.

RTMP

The RTMP is stream protocol, good for:

• Realtime: RTMP latency can be 0.8-3s.
• DRM: RTMPE/RTMPS encrypt protocol.
• Stable for PC flash.
• Server input: The actual industrial standard for encoder to output to server is RTMP.
• Fault Tolerance: The RTMP edge-origin can support fault tolerance for stream protocol.
• Monitor: The stream protocol can be monitored.

RTMP is bad for:

• Complex: RTMP is more complex than HTTP, especially the edge.
• Hard to cache: Must use edge to cache.

HTTP

The HTTP stream is the vod stream used for some video website:

HTTP is delivery files, good for:

• High performance: There are lots of good HTTP server, such as nginx, squid, traffic server.
• No small piece of file: The large file is good than pieces of file for HTTP cache.
• Firewall traverse: Almost all firewall never block the HTTP protocol.

HTTP is bad for:

• Large lantency: The http stream atleast N10s latency.
• Player does not support: Only PC flash can play http stream. Mobile platform does not support http stream.

HLS

HLS is the open standard of Apple. HLS is supported by Android3+.

HLS is good for:

• High performance: Same to HTTP stream.
• Firewall traverse: Same to HTTP stream.
• Mobile Platform standard: Apple IOS/OSX, Android and PC/flash support HLS.

HLS is bad for:

• Large lantency: The http stream atleast N10s latency.
• Pieces of file: CDN does not like small file.

MPEG-DASH

SRS3 supports DASH, please read #299.

Use Scenario

See HTTP and RTMP

I recomment to use these delivery protocols in:

• Encoder always output RTMP for internet server.
• Server always accept RTMP from encoder.
• The cluster use RTMP as internal delivery protocol.
• The low latency application on PC: Use flash to play RTMP.
• Application without low latency required: RTMP or HLS.
• The vod stream on PC: Use HLS or HTTP stream.
• Apple IOS/OSX: Always use HLS. Or use library to play RTMP, like https://www.vitamio.org
• Android: Always use HLS. Or use library to play RTMP.

Winlin 2014.11