1.
Specifying Multiple Delivery Schemes
You can also use multiple source elements to specify different delivery schemes. Let’s say you have a large real-time video streaming service that uses RTSP streaming, and you want to add support for Safari on iOS, including iPad, using HTTP Live Streaming, along with a progressive download for browsers that can’t handle either kind of streaming. As shown in Listing 1-4, with HTML5 video it’s quite straightforward.
<!doctype html>
<html>
<head>
<title>Multi-Scheme Video Player</title>
</head>
<body>
<video controls autoplay >
<source src="http://HttpLiveStream.m3u8">
<source src="rtsp://LegacyStream.3gp">
<source src="http://ProgressiveDownload.m4v">
</video>
</body>
</html>
https://developer.apple.com/library/archive/documentation/AudioVideo/Conceptual/Using_HTML5_Audio_Video/AudioandVideoTagBasics/AudioandVideoTagBasics.html
2.hls flv
兼容方案
PC端
1、优先使用 HTTP-FLV，因为它延迟小，性能也不差1080P都很流畅。
2、不支持 flv.js 就使用 Flash播放器播 RTMP 流。Flash兼容性很好，但是性能差默认被很多浏览器禁用。
3、不想用Flash兼容也可以用HLS，但是PC端只有Safari支持HLS
移动端
1、优先使用 HTTP-FLV，因为它延迟小，支持HTTP-FLV的设备性能运行 flv.js 足够了。
2、不支持 flv.js 就使用 HLS，但是 HLS延迟非常大。
3、HLS 也不支持就没法直播了，因为移动端都不支持Flash。
https://www.jianshu.com/p/4ff943817436