[FFmpeg-devel] Problem with DVD VOB encoding - NAV packets not included properly.
Neil Brown
neilb
Sun Jul 15 08:09:49 CEST 2007
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).
Thanks,
NeilBrown
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