[FFmpeg-user] Corrupt audio when transcoding uncompressed avi

[Carl Eugen Hoyos]

Am Fr., 10. Mai 2019 um 09:20 Uhr schrieb Camara Caamaño, Xavier
<xcamara at gencat.cat>:

> My institution has transformed an old SD telecine and added a 4K camera with a Decklink capture card.
> We are currently capturing Uncompressed avi.

What writes the uncompressed avi file?
The avi file is badly interleaved, while it is a bug in FFmpeg that it
mishandles the bad
interleaving, avi was not intended to write uncompressed 4k files...

> After capture, the file plays correctly (both video and audio).

What application did you test playback with?

> The problem comes when transcoding with ffmpeg (either transcoding to ffv1 or x264). After transcoding,
> the file plays incorrectly, with the sound playing only noise.

> We realized that if we start the transcoding a few seconds after the beginning, the ouput file comes out well.

Do you mean it works when seeking?

> So, we are assuming the problem is the original file with a messed up timestamp (?)

No, if you compare the console output of older and newer FFmpeg, you see the
difference: Old versions correctly detected the bad interleaving and handled it
accordingly.

> The error it gives us is:
>
> Invalid PCM packet, data has size 4 but at least a size of 6 was expected

That is an additional regression on top of the interleaving detection:
Some FFmpeg versions do not create white noise, just eat a part of the output.

[...]

>   configuration:  --disable-autodetect ...

Just curious: Why do you need nvenc, openh264 and x264?
(Or where did you find this binary?)

Carl Eugen