Fix two silent failures in vc2.sh: output ownership and NVDEC codec gating

[paxri01]

Two bugs found in one vc2 -m run on 2026-09-19. Both failed silently because their errors were being sent to /dev/null or suppressed by -loglevel quiet.

1. Output ownership was never applied

chown $user:$group on the output file and directory has been failing on every run. Changing a file's owner to another user requires root; the script runs as an ordinary user. sudo would not help either — the output shares are exported root_squash, so root has less access there than we do.

With stderr discarded and no return code checked, this was invisible: the chmod on the next line still succeeded, so the files looked as though the ownership block had run. Recent output is rp01:rp01; files from older runs are serviio:video.

Set only the group, which an ordinary member of it is allowed to do. Serviio reads through the shared video group, so rp01:video 0664 grants exactly what serviio:video 0664 did. Output directories also get the setgid bit so season subdirectories inherit the group. Failures are now logged.

2. -hwaccel cuda was applied to codecs the GPU cannot decode

-hwaccel cuda was set once at startup and used for every file. It is a decoder selection directive, not a hint: it replaces the software decoder with the native hwaccel shim, which has no software path. Given a codec NVDEC cannot decode there is no fallback — ffmpeg fails every packet in a loop and never stops.

An AV1 source hit this. The GPU is Turing, which has no AV1 decode block:

[vist#0:0/av1] Selecting decoder 'av1' because of requested hwaccel method cuda
[av1] format supported: no, max_mb_count: 0
[av1] Hardware is lacking required capabilities
[av1] Your platform doesn't support hardware accelerated AV1 decoding.
[dec:av1] Error submitting packet to decoder: Function not implemented

That block repeated 3673 times in 45 seconds, at ~180% CPU with no video written. It looked like a hang, and it was not: audio and subtitles kept encoding and were eventually muxed on their own. The abandoned temp file was 97 MB of audio and subtitles with no video stream, 4996s into a 5106s runtime. Left alone the run would very likely have exited 0, published that over the real film and moved the 1.7 GB source to done/.

Gate the flag on the probed $vCodec instead. AV1 joins the list only when the GPU reports compute capability >= 8.6, where NVDEC gained an AV1 decoder. ffmpeg -hwaccels cannot answer this — it reports that the method exists, never which codecs the silicon handles.

Also drops -loglevel from quiet to error. Quiet is what turned an ffmpeg failing loudly into seven minutes of silence; -stats still provides the progress line.

Verification

• bash -n and shellcheck -S warning clean.
• chgrp video + chmod confirmed to succeed as an ordinary user on both the plex and QNAP exports.
• The AV1 file decodes through libdav1d at 11.9x realtime and encodes on NVENC normally — all three streams present in the output. Full vc2 -m re-run prints NVDEC has no av1 decoder; decoding in software and proceeds.

🤖 Generated with Claude Code