[Webkit-unassigned] [Bug 194499] New: [MSE] Seek while seeking freezes playback

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Mon Feb 11 07:07:57 PST 2019


https://bugs.webkit.org/show_bug.cgi?id=194499

            Bug ID: 194499
           Summary: [MSE] Seek while seeking freezes playback
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKitGTK+
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: s.krutikov at activevideo.com
                CC: bugs-noreply at webkitgtk.org

Created attachment 361679

  --> https://bugs.webkit.org/attachment.cgi?id=361679&action=review

Test HTML5 application

Performing a seek while another seeking operation is in progress sometimes freezes playback. This happens consistently at the beginning of our test MSE video. The test scenario works properly in Chrome and Firefox, but fails in MiniBrowser and in our proprietary component which is also based on WebKitGTK.

Our investigation has shown that seek is delayed due to the seek position being outside of buffered ranges. However, the seek position is very close to one of the buffered ranges. This leads to a seek completion by media source code since it checks whether a position is buffered with some tolerance (https://github.com/WebKit/webkit/blob/master/Source/WebCore/Modules/mediasource/MediaSource.cpp#L240), whereas GStreamer private player uses exact matching (https://github.com/WebKit/webkit/blob/master/Source/WebCore/platform/graphics/gstreamer/mse/MediaPlayerPrivateGStreamerMSE.cpp#L297). Thus, the whole class stack in WebKit related to MSE playback goes to an invalid state. We fixed the issue using exact matching check in media source code as it is done in the private player. But we are not sure this is the proper fix.

Steps to reproduce the bug:
* Unzip the attached archive.
* Host and load mse.html - MSE video should start playing.
* Wait for approximately 2 seconds - double seeking will be triggered.

Expected result: seek operation succeeds, video playback continues.
Actual result: video playback freezes and never recovers.

WebKitGTK version: 2.23.3

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