Player doesn't recover when getting an download error on expired segments (live)

[AxelDelmas]

Server sends 404s when the player tries to download expired segments on this stream: http://wowza.streamroot.io/live/stream1/index.m3u8
To repro, play this stream and throttle the bandwidth to 750kbps from chrome debugger.

This part of the code should prevent this to happen: https://github.com/dailymotion/hls.js/blob/master/src/controller/buffer-controller.js#L203-L210

But this stream has variable segment length, which can cause several smaller segments to expire at once if a bigger segment is made available at live edge, and on top of that the total duration of the index is also variable.

This part of the code is executing only the first time we download the manifest:
https://github.com/dailymotion/hls.js/blob/master/src/controller/buffer-controller.js#L816-L818
so with the variable playlist duration this.seekAfterStalling = this.startPosition + sliding; might be before the start of the playlist when we need to seek.
Reevaluating this.startPosition everytime we reload the manifest seems to help.

A possible improvement could be as well to limit the max latency we can have from the live edge.
(maybe make the startPosition configurable as well, as a time distance from the live edge)

Another possible improvement would be to loosen the criticity of getting a download error on a fragment for live streaming and try seeking forward if we can't download a segment (with a limited amounts of retries).

[mangui]

now http://dailymotion.github.io/hls.js/demo/?src=http%3A%2F%2Fwowza.streamroot.io%2Flive%2Fstream1%2Findex.m3u8 autorecovers @ 750 kbps

[mangui]

closing as PR merged, and IO error are not fatal anymore on live streams