Support delayed create of SourceBuffer

[fightZy]

Is your feature request related to a problem? Please describe.

I have an M3U8 playlist with only audio data for the first few seconds, and then both audio and video data are available. At this point, hls.js will report an error because the video sourceBuffer cannot be found. By checking the hls.js code, I learned that the sourceBuffer seems to only be created during initialization based on the track type owned by the first ts file;

Describe the solution you'd like

Can you support changing existing sourceBuffers based on actual changes in track types? At least for me, I need to adapt to the addition of track types

Additional context

testUrl: https://cos-public.seewo.com/seewo-ms/uwiykxkvhkkjnhoyhmhoowxxlnphihhh.m3u8

[robwalch]

Mixed track configurations like this are not supported as MSE based playback requires all tracks be buffered before the media element will play though the SourceBuffers.

Still, you can detach and attach the media element or call recoverMediaError to reset the MediaSource when playback reaches the point where the second track becomes available (or is no longer available). It will be a very noticeable operation - the media element is emptied completely before setting back up in roughly a tenth to a half of a second.

Try fixing the issue in your HLS playlist so that each segment includes audio and video. Adding a GAP tag to the segment(s) with only audio will cause them to be skipped allowing for correct setup.

[fightZy]

Mixed track configurations like this are not supported as MSE based playback requires all tracks be buffered before the media element will play though the SourceBuffers.

Still, you can detach and attach the media element or call recoverMediaError to reset the MediaSource when playback reaches the point where the second track becomes available (or is no longer available). It will be a very noticeable operation - the media element is emptied completely before setting back up in roughly a tenth to a half of a second.

You really should address the issue in your HLS playlist so that each segment includes audio and video. Adding a GAP tag to the segment(s) with only audio will cause them to be skipped allowing for correct setup.

I have tried it, but it doesn't work because creating a sourceBuffer type is still determined from the first shard file

[robwalch]

I have tried it, but it doesn't work because creating a sourceBuffer type is still determined from the first shard file

That's because you need to playback to start on a segment with both tracks (when playback reaches the point where the second track becomes available). You can achieve this by seeking or setting startPosition.

[fightZy]

I have tried it, but it doesn't work because creating a sourceBuffer type is still determined from the first shard file

That's because you need to playback to start on a segment with both tracks (when playback reaches the point where the second track becomes available). You can achieve this by seeking or setting startPosition.

Okay, this can indeed be played normally from where there is video data, but segments with only audio data at the beginning cannot be played🤔