bugfix: Don't sync to live when media is in paused

[jony89]

This PR will...

fix issue when the video is in paused state yet still hls.js updating the video element current time.

this was fixed and merged in old versions (0.1.x) and probably got missed when refactoring base-stream-controller

see #2417

I was able to reproduce it in the demo page:

https://hls-js.netlify.app/demo/

choose Low Latency HLS Sample of Big Buck.. (or go directly to https://hls-js.netlify.app/demo/?src=https%3A%2F%2Fstream.mux.com%2Fv69RSHhFelSm4701snP22dYz2jICy4E4FUyk02rW4gxRM.m3u8&demoConfig=eyJlbmFibGVTdHJlYW1pbmciOnRydWUsImF1dG9SZWNvdmVyRXJyb3IiOnRydWUsInN0b3BPblN0YWxsIjpmYWxzZSwiZHVtcGZNUDQiOmZhbHNlLCJsZXZlbENhcHBpbmciOi0xLCJsaW1pdE1ldHJpY3MiOi0xfQ== )

and the following configuration :

{
  "debug": true,
  "enableWorker": true,
  "lowLatencyMode": true,
  "backBufferLength": 90,
  "liveSyncDurationCount": 3,
  "liveMaxLatencyDurationCount": 6
}

now click the pause button and see how the video frame is changing every 6 seconds.

Resolves issues:

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

question

the above fix works for me. but I am wondering whether _trySkipBufferHole and _tryNudgeBuffer in gap-controller need this check as well?

[jony89]

@robwalch ?

[jony89]

@lpommers any help here?

[lpommers]

@jony89 I'm not sure i'll be of much help here (I'm not really a maintainer or expert of hls.js).

I think you might want to fill out a bug report with a config, log, and test stream (if possible - can be hard with live). Testing one of my own live streams I wasn't able to reproduce the issue of the paused frame of the stream being changed.

You might also find these PRs/issues helpful for context:

• Live stream sync fixes and improvements #3603
• Time-shifting functionality with live streams? #4004

[jony89]

@robwalch not sure why the downvote? this PR is identical and the same issue as #2417

yet the condition was removed while refactoring.

[lpommers]

I think this is considered "works as expected" because v1 follows the pattern for native hls playback from the <video /> element in Safari.

My understanding is that live streams will continue to buffer up to specified amount. Eventually, the browser will remove media from the buffer and the player will need to seek to a buffered range, even if paused. If we were to take a live native <video /> in Safari, pause it and have the browser dump the whole buffer, it would have to seek the currentTime of the media to somewhere in the sliding playlist. Which is what hls.js seems to do as well...

(I agree though from UX/user perspective, it would be cool if browsers were able to keep the tiniest chunk of the buffer that is being visibly displayed, so that the frame does not visibly move)

[jony89]

so if the user click Pause, during Live streaming, it's sounds ok to you to change the frame every few seconds?

I was able to reproduce it in the demo page:

https://hls-js.netlify.app/demo/

choose Low Latency HLS Sample of Big Buck.. (or go directly to https://hls-js.netlify.app/demo/?src=https%3A%2F%2Fstream.mux.com%2Fv69RSHhFelSm4701snP22dYz2jICy4E4FUyk02rW4gxRM.m3u8&demoConfig=eyJlbmFibGVTdHJlYW1pbmciOnRydWUsImF1dG9SZWNvdmVyRXJyb3IiOnRydWUsInN0b3BPblN0YWxsIjpmYWxzZSwiZHVtcGZNUDQiOmZhbHNlLCJsZXZlbENhcHBpbmciOi0xLCJsaW1pdE1ldHJpY3MiOi0xfQ== )

and the following configuration :

{
  "debug": true,
  "enableWorker": true,
  "lowLatencyMode": true,
  "backBufferLength": 90,
  "liveSyncDurationCount": 3,
  "liveMaxLatencyDurationCount": 6
}

now click the pause button and see how the video frame is changing every 6 seconds.

@robwalch I can't see how this is work as expected behavior ?

[phillipseamore]

This happens because of liveMaxLatencyDurationCount being set to other than Infinity. You are telling hls.js that the maximum allowed delay from live is 6 segment durations.

You could possibly change liveMaxLatencyDurationCount to Infinity on pause and back again on play.

[jony89]

@phillipseamore thanks, indeed that is one workaround, that one can use for now, yet changing configurations just for pause to actually pause the video seems a bit hacky to me. so I keep this PR open and wait for more responses, unless you think this change is wrong?

[phillipseamore]

I see nothing wrong with the patch.

Personally I do feel pausing a live stream without a DVR window should behave more like stopping it completely (e.g. no more fetching playlists, chunks or updating time or the buffer). For streams with a window shorter than 1 minute I just tear down hls.js and throw a play button overlay over the video element (this could be an image grab of the last frame in the video element as well) and build it up on the rare occasion a user hits play again, saving me a little bit in server resources and bandwidth.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[jony89]

@robwalch can you please help me here, why did we merge #2417 yet this PR is not acceptable? they both are the same fix..

[robwalch]

@robwalch can you please help me here, why did we merge #2417 yet this PR is not acceptable? they both are the same fix..

Hi @jony89,

Even when playback is paused, HLS.js continues to buffer media, refresh live playlists, and adhere to the live sync logic as configured in the player API for the active HLS stream. In this case it's liveMaxLatencyDurationCount: 6 that triggers a seek to maintain a distance of 6 target durations or less.

If you would like to stop activity when paused so that the frame does not update, call hls.stopLoad() when the media element is paused, and hls.startLoad() when unpaused.