A corrective release of Firefox 127.0.2 is available, which resolves issues with video playback freezing on YouTube when changing position in the stream. The problem was caused by incorrect stream formatting in the VP9 format on YouTube's side and manifests, among other things, for VP9 videos at resolutions above 1080p.
The YouTube stream does not consistently provide increasing timestamps for incoming video segments, leading to situations where segments overlap in timing (for example, a segment with start and end timestamps of '124416000, 125126000' is followed by a segment with timestamps '125125000, 131382000', starting before the previous segment ends). Due to this timestamp mismatch in the stream, Firefox is unable to correctly calculate the start time of the next segment and skips such segments, not adding them to the buffer and waiting for them to arrive for playback, while YouTube assumes that the segments have been successfully received by the other side.
Additionally, a bug was fixed that caused the private mode icon to appear in the taskbar on Windows and displayed Firefox's private windows in separate groups when the browser.privateWindowSeparation.enabled parameter was set to false (after the fix, private and regular windows are displayed in the same group on the taskbar).
Source: opennet.ru
