Bugzilla

This issue is still caused by incorrect webm sample's endtime, which triggered the discontinuity check so that Firefox skipped the samples which should have been appended to the buffered range. We need a better way to determine the webm sample's end time, that can be done in bug 1903466.

From the profiled result, [here](https://share.firefox.dev/3xEH3wy) we can see the samples Youtube appended, but the [first and the second samples have the wrong end time](https://share.firefox.dev/3VHLA9Q). As there is an unexpected gap appearing between them, a lot of samples were [skipped unexpectedly](https://share.firefox.dev/4evngAr).

And the reason of why we didn't set the correct timestamp for the first sample is because the appended buffer only contained one frame `[46824993000, 46825009000]` (duration: 16000), and our webm demuxer [doesn't know how to handle that case](https://searchfox.org/mozilla-central/rev/7f7ea528f740dfbfd871c28362070982ef5f01e9/dom/media/webm/WebMDemuxer.cpp#619-649) because we don't know the duration and there is no previous timestamp.

This issue is still caused by incorrect webm sample's endtime, which triggered the discontinuity check so that Firefox skipped the samples which should have been appended to the buffered range. We need a better way to determine the webm sample's end time, that can be done in bug 1903466.

From the profiled result, [here](https://share.firefox.dev/3xEH3wy) we can see the samples Youtube appended, but the [first and the second samples have the wrong end time](https://share.firefox.dev/3VHLA9Q). As there is an unexpected gap appearing between them, a lot of samples were [skipped unexpectedly](https://share.firefox.dev/4evngAr).

And the reason of why we didn't set the correct timestamp for the first sample is because the appended buffer only contained one frame `[46824993000, 46825009000]` (duration: 16000), and our webm demuxer [doesn't know how to handle that case](https://searchfox.org/mozilla-central/rev/7f7ea528f740dfbfd871c28362070982ef5f01e9/dom/media/webm/WebMDemuxer.cpp#619-649) because we didn't know the duration and there was no previous timestamp.