Changing audio cause video buffer clear.

[avelad]

Have you read the FAQ and checked for duplicate open issues?: Yes

What version of Shaka Player are you using?: 2.5.0-beta2

Can you reproduce the issue with our latest release version?: Yes

Can you reproduce the issue with the latest code from master?: Yes

Are you using the demo app or your own custom app?: Both

If custom app, can you reproduce the issue using our demo app?: Yes

What browser and OS are you using?:
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36 (Chrome 70 - Ubuntu 18.04)

What are the manifest and license server URIs?:
https://storage.googleapis.com/shaka-demo-assets/angel-one/dash.mpd

What did you do?
Load the stream. Observe Buffer Info with getBufferedInfo(), change the audio language

What did you expect to happen?
Only audio buffer is cleared. We only change the audio not the resolution.

What actually happened?
Audio and Video buffer are cleared

[TheModMaker]

How are you changing the audio language? Are you using selectAudioLanguage or selectVariantTrack?

I'm fairly sure it should work with selectVariantTrack, but if you are using selectAudioLanguage, it may not because of how we switch streams. My guess would be that you do this early and ABR hasn't stabilized yet, so when we select a new track with the new preference, ABR selects a different video stream and so we clear the buffer.

[avelad]

I’m using selectVariantTrack

[TheModMaker]

It looks like when we clear the audio buffer, it triggers a seek to flush the media. Because the audio buffer is empty, it is considered an unbuffered seek and we clear everything. We shouldn't be doing this.