Bug 305208 – [MSE] Fix sample DTS to prevent deletion of preexisting samples when PTS doesn't conflict

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Enrique Ocaña]

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Let's consider a preexisting samples A, B, C, and a new sample N with the
following timestamps:

       Decoding time  Presentation time
       -------------  -----------------
Sample A: 827.826164000  827.826164000
Sample B: 827.826164100  827.826164100
Sample C: 827.826164200  827.826164200
Sample N: 827.826125000  827.909542000

These disparities in DTS vs. PTS offsets between samples A and B exist
because both samples come from completely different videos (eg: because
of ad insertion).

In a timeline:

DTS ···NABC·······
PTS ····ABC···N···

Judging by PTS, the samples A, B, C should remain and theoretically don't
need to be erased. However, considering DTS, the samples A, B, C have to
be erased, because the sample N would reach the video decoder earlier (by
decoding ordering) and change the state of the decoder, making it
unsuitable for samples A, B, C.

It would be nice to find a way to avoid erasing samples A, B, C in this specific
case.

[Enrique Ocaña]

Pull request: https://github.com/WebKit/WebKit/pull/56346

[Enrique Ocaña]

See: https://github.com/WebPlatformForEmbedded/WPEWebKit/issues/1542

[Enrique Ocaña]

Some of the detected test failures are caused by the fact that edit list support is disabled in WebKitGTK, and this is creating small offsets that trigger unnecessary "out-of-order frame detected" events.

I've also tested the patch in downstream wpe-2.38[1] (with edit lists support), running the layout test there, and the mediasource-config-change-mp4-v-framerate.html test at least passes, but video decoding errors appear. This is enough evidence to consider the fix as problematic.

I'm withdrawing this PR by now.

[1] https://github.com/WebPlatformForEmbedded/WPEWebKit/tree/eocanha/eocanha-debug-160

[Enrique Ocaña]

Re-opening for pull request https://github.com/WebKit/WebKit/pull/57363

[EWS]

Committed 307359@main (13a26d1f9065): <https://commits.webkit.org/307359@main>

Reviewed commits have been landed. Closing PR #57363 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/170225068>