[Bug]: App crashes when the playhead crosses a clip sourced from a legacy AV1 WebM recording

[blueraincoatli]

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Describe the bug

On Windows, when the timeline contains multiple clips and the playhead crosses a clip whose source recording is an AV1-encoded WebM produced by an older Openscreen version (recorded Dec 2025), the app crashes and exits with no error dialog. Only clips sourced from these legacy AV1 WebMs trigger the crash; clips from current-version H.264 recordings work fine.

To Reproduce

1. Import a legacy AV1 WebM recording (recorded by an older Openscreen version) as a clip
2. Add another clip to the timeline
3. Press play and let the playhead cross from one clip into the AV1-sourced clip
4. App crashes and exits

Evidence

ffprobe on the crashing recordings shows:

[libaom-av1] Unknown version 127 of AV1CodecConfigurationRecord found!
[matroska,webm] Unknown-sized element at 0x67dc8 inside parent with finite size

codec_name=av1
avg_frame_rate=0/0        (stream duration=N/A)

The files still decode fully (ffmpeg -f null succeeds), but the container structure and frame-rate metadata are malformed. Recordings made by the current version (H.264, avg_frame_rate=60/1) do not crash.

Expected behavior

The editor should handle or gracefully reject malformed legacy recordings instead of crashing when the playhead crosses the clip boundary.

Environment

• OS: Windows 11 Home China (build 26200)
• Openscreen version: 1.10.0 (exe installer)