[MEncoder-users] How to encode a DVD

[Nick Marinho]

 Very good explain, help me a lot.

 Thanks

2007/6/6, Jorge Peixoto de Morais Neto <please.no.spam.here at gmail.com>:
>
> > > 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.
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>



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