Possible causes
- The client does not support the video or audio codec.
- The container is supported but one internal stream is not.
Check in this order
- Inspect container, video, audio, subtitle, and channel layout separately.
- Test on a desktop reference player.
- Create a short H.264/AAC MP4 comparison sample.
Fix steps
- Choose a target-supported audio and video profile based on the failed stream.
- Retest the short sample before processing the full title.
When to escalate
Escalate when a documented compatible profile fails on the current client version and a second reference player.
If it is still unresolved, collect
- client model
- container
- video codec
- audio codec
- channel layout
Known log signatures
unsupported audio | unsupported codec | cannot play | no sound | decoder error
Evidence
- HandBrake container formats — checked 2026-07-12, review due 2026-10-10
- Plex supported media formats — checked 2026-07-12, review due 2026-10-10
- Jellyfin codec support — checked 2026-07-12, review due 2026-10-10