[MEncoder-users] Encoded DVD's appear too short

[Ben Nemec]

On Monday 07 November 2005 23:42, you wrote:
> On Mon, Nov 07, 2005 at 08:42:13PM -0600, Ben Nemec wrote:
> > Just a minor niggle here with the DVD's that I encode using MEncoder. 
> > For some reason the lengths of tracks that I encode with it show up about
> > half as long as they should in lsdvd and my standalone player.  I think
> > MPlayer pre7 may have identified them that way too, although I'm using
> > current CVS now and it gets the lengths right.  I've double-checked my
> > command-line options and as far as I can tell they're okay.  Here's my
> > command-line (with line breaks added):
> >
> > mencoder "$infile" -of mpeg -vf scale=720:-2,expand=720:480,harddup\
> >  -oac lavc -ovc lavc -lavcopts
> > acodec=ac3:abitrate=192:vcodec=mpeg2video:\
> > keyint=18:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:aspect=4/3\
> > -mpegopts format=dvd -srate 48000 -af lavcresample=48000 -ofps
> > 30000/1001\ -o temp.mpg
>
> -ofps 30000/1001 along with scaling is certainly wrong. If the content
> is interlaced, you need to treat it specially or deinterlace it first,
> and if it's not interlaced then 30000/1001 is almost surely the wrong
> framerate.

Hmm, I thought DVDs had to have a framerate of 30000/1001?  I'm not sure 
whether the input is interlaced or not (sorry, kind of ignorant about this), 
although it probably was originally.  It's a Myth recording and IIRC tv is 
(usually?) interlaced.  However, I've reencoded it to regular MPEG4 to get 
rid of the commercials and get it in a more widely supported format.  I would 
assume the interlacing gets removed during the MPEG4 encode, but like I said 
I'm ignorant when it comes to this.

> BTW why are you rescaling and adding black bars to make it 4:3?! This
> will only butcher the quality and make it so that the DVD can't be
> played right on 16:9 displays.

Hmm, good question.  Most of the input files I'm using are 4:3 since they're 
SDTV recordings so at the time that seemed like forcing any file I ran it on 
to be 4:3 would make things simpler (plus my TV is currently only 4:3 so I 
wasn't even thinking about wide aspect ones).  It's part of a script, so I 
wanted it to work with almost any file I gave it.  And at the time all I had 
heard was that DVD video under Linux was a pain so I wanted to simplify 
things by not dealing with aspect ratios (turns out it wasn't all that 
complicated with Mencoder and the docs, but I didn't know that).  

I suppose to have widescreen files work properly I would have to use a 
different command with the aspect being 16:9.  As long as I match up the 
original aspect with the appropriate 4:3 or 16:9 DVD aspect I should be okay, 
right? 

> > The resulting file is then passed to dvdauthor to create the disk
> > structure. Is this more likely an MEncoder problem or should I be looking
> > at dvdauthor? It's not a major issue, but it would be nice to get
> > accurate times for the resulting discs.  Thanks.
>
> No idea what you mean by the time being wrong.

Just that lsdvd and my standalone DVD player seem to think the discs are about 
half as long as they should be.  They play fine otherwise, but not having 
accurate times messes up seeking sometimes.

-Ben