[FFmpeg-user] Can't write packet with unknown timestamp

Carl Eugen Hoyos ceffmpeg at gmail.com
Wed Feb 13 17:25:57 EET 2019

2019-02-13 15:07 GMT+01:00, Brian J. Murrell <brian at interlinx.bc.ca>:
> A piece of software I'm using is trying to remux a file and running
> into an error:
> $ ffmpeg -f avi -i file:"/tmp/vid.avi" -sn -codec:v:0 copy -flags

Generally, you shouldn't force an input format and certainly
not for avi.

> -global_header -fflags +genpts

You want -fflags +genpts to have an effect on your input
$ ffmpeg -fflags +genpts -i vid.avi

> -vsync -1

This must be a bad idea with -c copy (or it has no effect).

> -map_metadata -1 -map_chapters -1

> -threads 0 -codec:a:0 ac3 -ac 6 -ab 192000  -y "/tmp/vid.mkv"

-threads 0 is the default, "-ac 6" can be bad, and I strongly
suggest not to re-encode ac3 audio to ac3, even less so with
a higher bitrate.

> ffmpeg version 4.0.3 Copyright (c) 2000-2018 the FFmpeg developers

For future questions, please remember that only current FFmpeg
git head is supported here.

Carl Eugen

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