Re-think gap-jumping and stall-detection

[joeyparrish]

I believe gap-jumping and stall-detection could use a redesign. It's not clear that the current algorithms were built with the right requirements in mind.

Let's use this issue:

1. to discuss requirements and decide what we should be designing/building
2. to track progress on rebuilding gap-jumping and stall-detection

In #3188 (comment), I suggested:

I would like to get rid of the "small/large" gap concept, to always jump gaps by default, and to completely rethink the behavior and triggers of gap-jumping. I also think it would benefit from combining with stall detection.

Here are other issues that may be related to gap-jumping and could/should be solved by whatever we do next:

• Support a grace period to avoid stalling on gap in live manifest #1864
• How to ignore a segment and buffer next segment? #2144
• Seek never completes with target before buffer and inside small gap limit #2247
• Stall detector cause the error "The play() request was interrupted by a call to pause()" on SmartTV #2920
• Configurable stall detector #3008
• Gap detection is not consistent accross browsers (VP9/Opus) #3059
• Long wait time for Stalled Playback: Reference Issue https://github.com/google/shaka-player/issues/2131 #3076
• Playback stalled after using a "skip back" feature #3089
• Inconsistent Chrome Stall At Discontinuities #3118
• Tizen 4 2018 encrypted playback got stuck.  #3344
• Don't jump over the gap at the beginning before the video is played so that the video poster doesn't disappear. #3451
• Handling HLS Large Gap Between SSAI and Live Segment Discontinuity #3560

[avelad]

I would also like to remind this problem: #3163 which happened only on some platforms.

[avelad]

@joeyparrish Do you think it would be possible to apply this also when we use the src= mode?

[joeyparrish]

I could be wrong (I can't memorize the codebase any more 😁), but I thought gap-jumping and stall-detection were applied generically regardless of playback type. If they aren't yet, we can make that a requirement for the new system.

[OrenMe]

Would be great to get some of the ideas suggested taken into consideration.
For us the main issues are around playback on smart TVs where the play pause definitely doesn't always help and we have added our own mechanism to combine small seeks as well to get out of player getting stuck.

[beka-discovery]

What is the process of Redesigning the feature @joeyparrish? We might be able to contribute and possible stay on top of design and execution. As long as we have a clear understanding of the process and what you have in your head.

[zuzzurro]

As @beka-discovery I'm myself extremely interested in any news about this story. Do you guys have anything to say about the development?
I think I have seen in the changelog for 5.0 that you got rid of the big gap handling, is that change related to this issue?
Any news would be extremely welcome because we are suffering a lot from gap handling in SSAI ads.