Modify SimulcastConsumer to keep using layers without good scores

[ggarber]

We have cases were some simulcast consumers get all the video layers disabled very often when the producers have a high amount of packet loss. In those cases we see up to 5-6 transitions per minute from "no layers" <-> "first layer" and we end up with frozen video or black video depending on when it happens.

I think mediasoup doesn't need to have the logic to estimate the quality of the producer streams because of these reasons:

• In many use cases it can be better to have bad quality video that no video at all.
• The current logic is creating many transitions (5-6 constantly per minute in some of our user reports) that makes the experience not very stable.
• With this change an app listening for the 'layerschange' event from the consumer will know that if layers have changed is because of the bandwidth estimation available instead of for a combination of multiple factors (bandwidth estimation and score of the producer). So it is easier to present that information in the UI.
• The current logic can be implemented by the app checking the producers scores if it is important.
• This way the logic is simpler.
• I haven't seen this logic in other SFUs like Janus/Signal/Jitsi.... (I could be wrong and it is not a strong reason per se, but just fyc).

If it is better to open this as an issue or forum post instead of a PR let me know. Thx for taking a look.

[jmillan]

LGTM.

Makes sense to me.

[ibc]

I assume this should be also changed in SvcConsumer, right?

[ggarber]

@ibc This logic was only available in SimulcastConsumer and not SvcConsumer. Probably another reason apart from the ones mentioned in the description to remove it from SimulcastConsumer.

[ibc]

I think this is ok. Will merge and release today.

[ibc]

Published in 3.9.11