[MEncoder-users] How to encode a DVD

[Jorge Peixoto de Morais Neto]

> > The movie is NOT being cropped down to 16:9. 
> 
> If the video has square pixels (which is just about the only way
> you're going to find a video with a 2.35:1 aspect) then yes, you do
> crop or expand to 16/9 directly.
The problem is that I don't consider the black borders as part of the
movie, so the sentence seemed wrong to me. But rereading, it doesn't
say that the movie will be 16/9, it says "add black borders or crop the
movie down to 16:9", which can be correct.

But forget this. the problems is that not mentioning DAR is very
misleading. 

That page should be informative enough so that someone
of reasonable intelligence, but only minimal video encoding
knowledge, should learn how to encode a video for DVD. Why doesn't the
page explain what a DAR is, or at least provide a link? 

I think the text below the table in section 14.8.1.1 should me moved to
section 14.8.2.1. And the two first sentences should be
replaced by a more explicative text. How about:

"Aspect ratio is the ratio between width and height of an image.
The aspect ratio of the image (including black borders)
generated by a DVD player is defined by the DAR - Display Aspect Ratio
- which is a number (4/3 or 16/9) stored on the DVD disc. The DAR
 is chosen trough -lacopts aspect=4/3 or -lavcopts aspect=16/9.
The image is expanded according to the DAR before being shown on TV. For
example, if the image is encoded in 720x480 and DAR=16/9, it is
expanded to 853x480, as 853=480*16/9. If DAR=4/3, it is shrunk
to 640x480. Remember this when calculating
the width and height of the encoded movie. For example, if the movie is
576x304, and you want to encode it in 720x480 and DAR=16/9, you can
scale it to 720x448, then add horizontal black borders to
reach 720x480. This can be accomplished with -vf
scale=720:448,expand=720:480. The picture will be shown at 853x480, so
the movie will be shown at 853x448: 853/448=576/304. Notice that
853/(576/304)=450.2, but we rounded it to the nearest multiple of 16 -
448. For better encoding efficiency, choose movie dimensions multiple
of 16, and align the black borders at 16-pixel boundaries. See
http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-dvd-mpeg4.html#menc-feat-dvd-mpeg4-constraints
for technical details."

Also, the table in section 14.8.1.1 should say "Display Aspect
Ratio" (or "DAR" to save space) instead of just "Aspect". This will be
more exact, and will clue the user that there is this DAR thing he must
take into account.

And section 14.8.5.2. gives this example:

mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf 
-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000 -lavcopts
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:\
keyint=18:vstrict=0:acodec=ac3:abitrate=192:aspect=16/9 -ofps
30000/1001 -o movie.mpg movie.avi

Which does not seem a good example. AFAIK, selecting -ofps 30000/1001
will result in hard telecine, which is very wasteful. The example 
should include soft telecine. 

If you agree with my suggestion, I will email it to whoever maintains
the mencoder documentation.

> > than next time my girlfriend asks me to make her a movie I will
> > make a SVCD.
> 
> With SVCD, you're limited to a lower resolution, and CDs have a much
> smaller capacity, requiring you either use rather low quality, or
> split across multiple discs.
Provided the image isn't too ugly, she will not mind. The
only way I will ever know if the image is ugly is if I test it.