Troubleshooting Playback

Playback won’t start (endless spinner)

Likely cause: FFmpeg is taking too long to initialize, especially with 4K content, image-based subtitles (PGS), or HDR tonemapping.

Solutions:

• Check server CPU usage — if it’s maxed out, another transcode may be running
• Disable subtitles temporarily to rule them out
• Check server logs: docker logs dubby | grep -i transcode
• Enable hardware acceleration if using software transcoding

Video stutters or buffers frequently

Likely cause: Network congestion, or the server can’t transcode fast enough.

Solutions:

• Check server CPU/GPU usage during playback
• Ensure the transcode cache (/cache) is on an SSD
• Reduce other network load on the same connection

No audio

Likely cause: Unsupported audio codec or channel mismatch.

Solutions:

• Check supported formats for your device
• On Android TV, AAC via HDMI passthrough can cause silence — the server should transcode to AC3 automatically. Restart the session if it doesn’t.
• Verify your receiver/soundbar is set to the correct input

Audio out of sync

Likely cause: Timestamp desynchronization after seeking, especially with complex audio formats.

Solutions:

• Restart playback from a nearby position
• If it persists, check the server logs for transcode errors
• Try a different audio track if the file has multiple

Video plays but is black (Apple TV)

Likely cause: HEVC content served in MPEG-TS segments instead of fMP4.

Solution: Update to the latest Dubby version. This is handled automatically in current releases.

DTS or lossless audio not playing

DTS and TrueHD support varies by device:

Device	DTS	TrueHD
Web	Transcoded to AAC	Transcoded to AAC
Apple TV	Transcoded to AC3	Transcoded to AC3
Android TV	Passthrough via HDMI	Transcoded to AC3
Shield Pro	Passthrough via HDMI	Passthrough via HDMI

For full lossless audio support, use an NVIDIA Shield Pro connected to an AV receiver via HDMI.

HDR content looks washed out

Likely cause: Your device doesn’t support the source HDR format, and tonemapping is converting to SDR.

Solutions:

• Check device profiles to verify HDR support for your device
• Ensure your TV/monitor has HDR enabled
• For Dolby Vision, only Shield Pro supports all profiles natively

Checking server logs

Server logs are the best way to diagnose playback issues:

# Follow logs in real-time
docker logs -f dubby

# Filter for streaming/transcode messages
docker logs dubby 2>&1 | grep -i "stream\|transcode\|ffmpeg\|session"

# Increase log verbosity
# Add to your docker-compose.yml environment:
LOG_LEVEL=debug

With debug logging, you’ll see the full playback plan including which tier of the playback hierarchy was selected, which codecs are being transcoded, and the FFmpeg command being used.