ATSC 3.0 AC-4 audio crashes ffmpeg ("Assertion 0 failed at ac4dec.c:4186")

[snake98 18]

i all, I'm hitting the same AC-4 crash on the latest server, so here are clean samples and logs in case they help.

 

SETUP

• Emby Server 4.10.2.0 (Windows)

• Bundled ffmpeg: 5.1-emby_2023_06_25_p6

• Tuner: HDHomeRun FLEX 4K (HDFX-4K), firmware 20260326, antenna, ATSC 3.0

 

WHAT HAPPENS

• 2 of my 3 unencrypted ATSC 3.0 channels can't be played through Emby. Any playback that needs the audio converted fails with "Error starting ffmpeg".

• The ffmpeg transcode log ends with:

Assertion 0 failed at src/libavcodec/ac4dec.c:4186

• ffmpeg aborts (exit code 3). Even plain ffprobe on the recorded file aborts with the same line.

• A third ATSC 3.0 channel (also AC-4, 5.1 + stereo) decodes fine, so it seems to depend on something in the particular AC-4 stream.

 

HOW TO REPRODUCE

I recorded 30 seconds of each channel straight from the HDHomeRun (/auto/vXXX.X?duration=30):

 

ffmpeg -i atsc3-126.1-sample.ts -map 0:a:0 -c:a aac -f null - → assertion, exit 3

ffmpeg -i atsc3-159.1-sample.ts -map 0:a:0 -c:a aac -f null - → assertion, exit 3

ffmpeg -i atsc3-147.1-sample.ts -map 0:a:0 -c:a aac -f null - → works (for comparison)

 

Streams on the working channel: HEVC Main 10 1080p, AC-4 5.1 (eng), AC-4 stereo (spa).

 

ATTACHED

• atsc3-126.1-sample.ts: fails

• atsc3-159.1-sample.ts: fails

• atsc3-147.1-sample.ts: works (comparison)

• ffmpeg transcode log + server log (from Dashboard → Logs)

atsc3-147.1-sample.ts atsc3-159.1-sample.ts atsc3-126.1-sample.ts ffmpeg-transcode-97d7453a-0304-49fd-9da8-45b42ac3ed9c_1.txt