video-audio-caption download correlation

[kuznetcoff777]

Have you read the FAQ and checked for duplicate issues:yes

What version of Shaka Player are you using:v2.1.6

Can you reproduce the issue with our latest release version:yes

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

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

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

What browser and OS are you using:chrome/ff

What are the manifest and license server URIs:
(you can send the URIs to shaka-player-issues@google.com instead, but please use GitHub and the template for the rest)

**What did you do?**opened stream and waited

What did you expect to happen? stream must play as fast as possible

What actually happened? several seconds to wait additionally

I throttled chrome to low network speed and saw that palyer downloaded segments in this way:
video-fragment-1(downloaded)
audio-fragment-1(downloaded)
caption-fragment-1(downloaded)
audio-fragment-2(downloaded)
caption-fragment-2(downloaded)
audio-fragment-3(downloaded)
caption-fragment-3(downloaded)
audio-fragment-4(downloaded)
video-fragment-2(still downloading)
caption-fragment-4(downloaded)
audio-fragment-5(downloaded)
caption-fragment-5(downloaded)

So video/audio/caption downloading is not correllated. If player have no video, why downlaod audio and caption? The same problem i described at Dash-Industry-Forum/dash.js#1319
Can you make same fix here? It will be very helpful for low speed users.

[joeyparrish]

From the dash.js code you referenced, it would seem that you want us to avoid buffering more audio than we have already buffered for video. Is that correct?

Can you explain the problem a bit more? Why is it wrong to buffer video and audio independently?

Do you expect us to wait until a video segment is buffered before fetching the corresponding audio segment? Or fetch them simultaneously?

[kuznetcoff777]

"you want us to avoid buffering more audio than we have already buffered for video. Is that correct?" - correct
"Do you expect us to wait until a video segment is buffered before fetching the corresponding audio segment? Or fetch them simultaneously?" - both methods wiil be ok, because at the moment available bandwith is used for downloading future audio-captions, but this bandwith could be used to download necessary video segment:

[kuznetcoff777]

So, is it possible?

[joeyparrish]

I think this is feasible. Tentatively scheduled for v2.3.

[joeyparrish]

We hadn't planned to work on this right now, but it came up while working on another issue. It seems to help that other issue, and it is fairly simple, so we will clean it up and try to get it out soon.

[joeyparrish]

Fix cherry-picked to v2.3.5.

[kuznetcoff777]

@joeyparrish Thanks!