Video.js fails to re-buffer after a switch from alternate to main HLS audio tracks (ts), but only when the video is fully buffered

[philcluff]

Description

When playing back content with an alternate audio tracks in HLS, users can switch freely between audio tracks during playback using the headphones menu in the corner.

In general this works as expected, and the user can swap back and forth.

However, if the stream is fully buffered, switching from a secondary audio track (unmuxed ts), back to a primary audio track (muxed ts) will cause playback to stall permanently.

Switching back from the secondary to primary muxed audio prints the following logs when the stall happens:

VIDEOJS: DEBUG: VHS: SourceUpdater > Removing 0 to 300 from audioBuffer
VIDEOJS: DEBUG: VHS: SourceUpdater > Removing 0 to 300 from videoBuffer

Here's a video demonstrating the issue: https://stream.new/v/OQksRvTDOb3bpOtGfoKKu00D8nu3fTLuoIrC00c2rrTJY

This is also reproducible with Apple's Bipbop stream, if you seek right to the end: https://devstreaming-cdn.apple.com/videos/streaming/examples/bipbop_16x9/bipbop_16x9_variant.m3u8

Unfortunately this means that for short TS packaged HLS videos with multiple audio tracks it's possible to reliably stall playback.

Reduced test case

https://stream.mux.com/LBLes3TWmz8KLRZgDOwU01WTzcag8l3lR.m3u8

Steps to reproduce

1. Load Video.js latest, for example use https://philcluff.co.uk/players/videojs-latest.html
2. Play this stream: https://stream.mux.com/LBLes3TWmz8KLRZgDOwU01WTzcag8l3lR.m3u8
3. Seek to ~4:45, and make sure the video has finished buffering to the end of the stream
4. Switch to alternate language (French)
5. Switch to back to the main audio
6. Observe the video re-buffers and stops playing

Errors

None

What version of Video.js are you using?

8.5.2

Video.js plugins used.

No response

What browser(s) including version(s) does this occur with?

Chrome 115.0.5790.170

What OS(es) and version(s) does this occur with?

MacOS

[video-archivist-bot]

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[misteroneill]

Thanks for the detailed report, Phil!

[adrums86]

+1 to what @misteroneill said. This is interesting one. It seems perhaps we have a race condition here, I noticed we're engaging some endOfStream logic here that appears to be getting into a bad state when we switch languages and clear the audio buffer around the same time. Will keep digging.

[adrums86]

Moving this to VHS.

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