[FFmpeg-devel] Problem with DVD VOB encoding - NAV packets not included properly.

[Michael Niedermayer]

Hi

On Sun, Jul 15, 2007 at 10:39:07AM +0200, V?ctor Paesa wrote:
> Hi,
> 
> V?ctor Paesa said:
> > Hi,
> >
> > Michael Niedermayer said:
> >> Hi
> >>
> >> On Sun, Jul 15, 2007 at 04:09:49PM +1000, Neil Brown wrote:
> >>>
> >>> Hi,
> >>>  I've been working with kdenlive (which uses the MLT framework which
> >>> uses the ffmpeg libraries) to make a DVD and found that the VOB
> >>> created does not have the correct NAV packets.
> >>>  This shows up when I run dvdauthor as it cannot find places to put
> >>> chapter links, and when viewing the DVD on a DVD player as
> >>>  fast-forward and rewind don't work properly.
> >>>
> >>>  The "dvd" format is being requested by kdenlive, but the NAV packets
> >>> don't get produced - well to be fair, a 22 minute VOB had 6 NAV
> >>> packets rather than the expected 2600 odd.
> >>>
> >>>  I looked through the code and found that in libavformat/mpegenc.c,
> >>> in
> >>> mpeg_mux_write_packet, towards the end, is this code fragment:
> >>>
> >>>     if (s->is_dvd){
> >>>         if (is_iframe && (s->packet_number == 0 || (pts -
> >>> stream->vobu_start_pts >= 36000))) { // min VOBU length 0.4
> >>> seconds (mpucoder)
> >>>             stream->bytes_to_iframe = av_fifo_size(&stream->fifo);
> >>> stream->align_iframe = 1;
> >>>             stream->vobu_start_pts = pts;
> >>>         } else {
> >>>             stream->align_iframe = 0;
> >>>         }
> >>>     }
> >>>
> >>>
> >>>  If I remove the assignment of 0 to align_iframe in the 'else'
> >>> clause,
> >>> the code appears to work.  i.e. I get lots of NAV packets, dvdauthor
> >>> correctly sets all of the chapter points, and FF/REW works properly
> >>> in my DVD player.
> >>>
> >>>  I confess that I only have a shallow understanding of this code, and
> >>> it could be that my change has some unintended consequences.  I would
> >>> appreciate if it someone more familiar with the code would check if
> >>> this is an appropriate change and hopefully get the problem fixed.
> >>>
> >>>  I am quite happy to test any alternate changes to make sure they
> >>> still do the right thing on my files if that will help.
> >>>
> >>>  (Yes, I have checked current SVN code).
> >>
> >> if it is reproduceable with (unmodified) command line ffmpeg then
> >> please provide full uncut output + used command line of it
> >>
> >> also the code you change is there since 2004, could you try some old
> >> svn versions to check if they generated nav packets properly
> >> and if not then iam a little curious why noone complained yet but
> >> ignoring that, your suggested fix looks correct but i first would like
> >> to understand the issue better also iam not maintainer of the mpeg
> >> muxer code, so i wont approve this change ...
> >>
> >> also did nav packet generation/dvd encoding work for anyone?
> >
> > I recall vaguely a problem involving reading from a VOB with NAVs using
> > vcodec copy that would fail to pass on the proper number of NAVs.
> >
> > I'll try to find it.
> 
> Here it is:
> http://thread.gmane.org/gmane.comp.video.ffmpeg.user/8662

does it work if the above mentioned align_iframe = 0 is removed?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20070715/31847e69/attachment.pgp>