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[tor-commits] [Git][tpo/applications/tor-browser][tor-browser-128.8.0esr-14.5-1] Bug 1924070 - modify H.264 extradata to match sample conversion code....

Title: GitLab

morgan pushed to branch tor-browser-128.8.0esr-14.5-1 at The Tor Project / Applications / Tor Browser

Commits:

  • 4224ae27
    by John Lin at 2025-03-10T15:04:22+01:00 
    Bug 1924070 - modify H.264 extradata to match sample conversion code. r=media-playback-reviewers,alwu

In AVC stream, NAL unit is represented with the length of unit data
(NALUnitLength) followed by the actual unit data(NALUnit). The NALUnitLength
field can be 1-4 bytes long and the size can be derived from the
'lengthSizeMinusOne' value recorded in extradata.
H264ChangeMonitor.CheckForChange() reformats all input samples so that
NALUnitLength will always be 4 bytes long while the original extradata is
used during decoder creation earlier, so decoder won't be able to correctly
parse converted samples if extradata is not modified accordingly.

Differential Revision: https://phabricator.services.mozilla.com/D239547

1 changed file:

Changes:

  • dom/media/platforms/wrappers/MediaChangeMonitor.cpp
    ... ... @@ -42,6 +42,14 @@ class H264ChangeMonitor : public MediaChangeMonitor::CodecChangeMonitor {
    42 42 
           : mCurrentConfig(aInfo), mFullParsing(aFullParsing) {
    43 43 
         if (CanBeInstantiated()) {
    44 44 
           UpdateConfigFromExtraData(aInfo.mExtraData);
    45 
    +      auto avcc = AVCCConfig::Parse(mCurrentConfig.mExtraData);
    46 
    +      if (avcc.isOk() && avcc.unwrap().NALUSize() != 4) {
    47 
    +        // `CheckForChange()` will use `AnnexB::ConvertSampleToAVCC()` to change
    48 
    +        // NAL units into 4-byte.
    49 
    +        // `AVCDecoderConfigurationRecord.lengthSizeMinusOne` in the config
    50 
    +        // should be modified too.
    51 
    +        mCurrentConfig.mExtraData->ReplaceElementAt(4, 0xfc | 3);
    52 
    +      }
    45 53 
         }
    46 54 
       }
    47 55

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