The new functionality for handling media tracks on demuxer level is currently covered by only basic unit tests. We'll need more test coverage, a few things that need improvement:
1. Currently tests cover only a couple of .webm and .mp4 files. We need to include more test files (preferably generated by different tools - ffmpeg, GPAC, etc).
2. Need to include test files with wider ranges of supported media track parameters (various languages, varying number of tracks, track ids not starting at 1, etc).
3. Perhaps include some files that are corrupted and have out-of-spec track values in them, to ensure those files are properly handled/rejected.