[FFmpeg-devel] [RFC]Add int64_t probesize2 to AVFormatContext

Oliver Fromme oliver at fromme.com
Mon Jul 28 10:29:24 CEST 2014

Eli Kara wrote:
 > > From: ffmpeg-devel-bounces at ffmpeg.org [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf Of Nicolas George
 > > Sent: Monday, July 28, 2014 1:10 AM
 > > That would be nice, thanks for proposing. But that would not fix
 > > the issue: not all MPEG-PS files come with a DVD structure, even
 > > ones with subtitles, people often dump the MPEG-PS stream and
 > > discard the corresponding IFO files.
 > It would solve the problem for DVDs with structure, which is probably
 > what most people have when they rip a DVD.
 > Just out of curiosity - why isn't DVD/BR reading implemented in
 > FFmpeg? Is it because of the encryption that needs to be cracked?
 > I'm asking because I couldn't find any explanation in the FAQ. It
 > seems weird no one has ever needed it before..

I need it all the time.  :-)

My dvd-to-mkv script uses "mplayer -dumpstream" to dump one
title from a DVD to disk.  Then I use ffmpeg to encode it
to h.264 ...  That's why I appreciate the patch very much
that Carl Eugen has created.

There's another problem:  The palette of the subtitle streams
is contained in the IFO files, too.  So, in order to get the
palette right, my script uses "mencoder -vobsubout", then
greps the palette from the resulting .idx file and feeds it
to ffmpeg's -palette option.

However, since I'm quite familiar with the DVD format, I have
recently written my own little tool that is able to extract
the palette from IFO files or DVD images, so I don't need
mencoder anymore and all of its dependencies.  I also plan
to extend it to be able to dump the MPEG-PS, so mplayer isn't
needed anymore either.

The only problem left is that subtitle streams sometimes
begin beyond the 2 GB boundary, which Carl Eugen's patch will
hopefully fix.

An alternative (and even better) solution would be if I could
tell ffmpeg that I *know* there *is* a VOBSUB subtitle stream,
and that there's no need to try to probe for it first.  That
would get rid of the huge delay that the probing incurs when
scanning several GB (which is a real PITA).  Maybe I'll try to
make a patch that can do this, like "-assume_vobsub 21" for
subtitle stream #21, or similar.

By the way, encryption is not an issue, at least not for me.
The VIDEO_TS structures and images that I use have already
been decrypted before.

One final remark:  Even if ffmpeg supported reading from DVDs
itself, I would still need to handle dumped MPEG-PS files.
That's because my script requires them anyway because it
performs a bunch of analysis steps on them.

Best regards

``We are all but compressed light'' (Albert Einstein)

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