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

Commits:

• 2aa78353
  by John Lin at 2025-03-10T14:20:42+00:00

  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:

• dom/media/platforms/wrappers/MediaChangeMonitor.cpp

Changes:

       : mCurrentConfig(aInfo), mFullParsing(aFullParsing) {

     if (CanBeInstantiated()) {

       UpdateConfigFromExtraData(aInfo.mExtraData);

+      auto avcc = AVCCConfig::Parse(mCurrentConfig.mExtraData);

+      if (avcc.isOk() && avcc.unwrap().NALUSize() != 4) {

+        // `CheckForChange()` will use `AnnexB::ConvertSampleToAVCC()` to change

+        // NAL units into 4-byte.

+        // `AVCDecoderConfigurationRecord.lengthSizeMinusOne` in the config

+        // should be modified too.

+        mCurrentConfig.mExtraData->ReplaceElementAt(4, 0xfc | 3);

+      }

     }

   }