[FFmpeg-user] Distorted output when encoding DVD as MP4, error message "ignoring pic cod ext after 0"

[Hans Carlson]

On Sat, 20 Jun 2020, M v D wrote:

> I'm trying to convert a number of DVDs to MP4. Some of them work, others
> result in lots of error messages and distorted output. All of them play
> correctly in VLC if I open the IFO file, but the ones that give distorted
> output fail to play in DVD if I open the VOB file. I'm using the following
> command:
>
> ffmpeg -i 'concat:VTS_02_1.VOB|VTS_02_2.VOB|VTS_02_3.VOB|VTS_02_4.VOB'
> out.mp4
>
> What stands out to me is that this message is only present for the DVDs
> that fail:
>
> [mpeg2video @ 0x7fffcfcfc0c0] ignoring pic cod ext after 0
>
> More output, including lots of error messages for each frame, is included
> below.
>
> Does anyone know what this means and how I can fix it? Thanks in advance
> for any help!

The short answer is -- don't do this.  Use mplayer -dumpstream to create a 
single .vob file, then use ffmpeg to convert that .vob to .mp4.

The longer answer is -- unfortunately, there are many links on the web 
that suggest the approach you tried, but as you discovered it doesn't 
always work.  And that's because vob files on a dvd are not as simple as 
they might appear.

There are multiple threads on this subject in the ffmpeg archives, I 
suggest you do a little searching and read through some of them if you 
want to understand why your original approach doesn't always work.

Try searching the ffmpeg mailing list with the following search 
parameters:

   site:lists.ffmpeg.org/pipermail/ffmpeg-user/ vob
   site:lists.ffmpeg.org/pipermail/ffmpeg-user/ dvd

Not everything in those results will be relevant to your question, but you 
should find several threads that are related.