[Webkit-unassigned] [Bug 212131] New: Audio drift on HLS videos that encrypted with AES-128

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=212131

            Bug ID: 212131
           Summary: Audio drift on HLS videos that encrypted with AES-128
           Product: WebKit
           Version: Safari 13
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Media
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: jatesadakarn at inox.co.th

Created attachment 399825

  --> https://bugs.webkit.org/attachment.cgi?id=399825&action=review

Some error message when drifting happens

We found that playing HLS videos (MPEGTS segments) that encrypted with AES-128,
on Safari on iOS 13.4, has some video/audio out-of-sync issues:

1. The video starts normally, no out-of-sync issues.
2. As the video playing, the audio keep out-of-sync, ahead of the video incrementally.
3. If user seek the video, the audio will back to be sync with the video again.
4. The drifting will occur again after a while.

We already investigate that:

* No drifting on older iOS versions.
* No drifting on iOS 13.4 with unencrypted HLS videos.
* No drifting on iOS 13.4 if the video is forced to play with MSE (on iPadOS).
* Also found this issue on Safari 13.2 (WebKit 15610.1.12.2) on Mac OS X.

When this issue occurs, there are some error log like this from mediaserverd:

Too few bits left in input buffer
Error deserializing packet
ACMP4AACBaseDecoder.cpp:1392:ProduceOutputBufferList: (0x159637640) Error decoding packet 2583: err = -1, packet length: 371
ACMP4AACBaseDecoder.cpp:1401:ProduceOutputBufferList: '21 11 45 00 14 50 01 46 FF F1 0A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5A 5D E9 82 14 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 B4 47 40 11 1A 00 42 F0 25'

We also prepare sample videos for reproducing this issue:
* Encrypted HLS video (that the drifting occurs):
    * Media: https://champjss-apple-hls-sync-issues.sgp1.cdn.digitaloceanspaces.com/blip-blop/encrypted/prog_index.m3u8
    * Sample Experience: https://youtu.be/y_9CQSfjRwY
* Unencrypted HLS video:
    * Media: https://champjss-apple-hls-sync-issues.sgp1.cdn.digitaloceanspaces.com/blip-blop/raw/prog_index.m3u8
    * Sample Experience: https://youtu.be/0HG_lpcR0Mc

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