Anything else (matroska/webm, ogg, wav, mp3, flac, …) → mediabunny,
dynamically imported so the MP4 path stays free of the cost.
Truly unknown magic bytes → try mp4box first (some odd files have
non-standard headers), then fall back to mediabunny.
When the Tier 2 kill-switch (importTier2: false) is set,
non-ISOBMFF files revert to the pre-Tier-2 stub-probe behaviour so the
rollout doc's "Tier 1 unchanged" guarantee continues to hold.
Probe a media file to detect available streams without extracting samples.
Dispatches based on the file's container — detected from the first 16 bytes, not the filename — to the right backend:
When the Tier 2 kill-switch (
importTier2: false) is set, non-ISOBMFF files revert to the pre-Tier-2 stub-probe behaviour so the rollout doc's "Tier 1 unchanged" guarantee continues to hold.