[MEncoder-users] mencoder size and aspect ratios for H.264 video

[Etienne Buira]

On Sun, Oct 04, 2009 at 10:32:23PM -0400, John Ratliff wrote:
> 
> > I have no trouble with the following cmdline:
> > $ mkvmerge -o mkv.mkv --aspect-ratio 0:16/9 tst.avi
> >
> > The video plays well in 16/9 (tst.avi's AR is 4/3).
> >   
> I can't find anyplace it mentions this in the mkvmerge man page, but the
> --apsect-ratio option must come before the video stream.
> 
> i.e.
> 
> mkvmerge -o movie.mkv --aspect-ratio 0:16/9 -A video.x264 audio.ogg
> works
> 
> mkvmerge -o movie.mkv -A video.xa64 audio.ogg --aspect-ratio 0:16/9
> doesn't work
> 
> I thought I had tried that, but maybe not. Thanks for the advice.

Well, --aspect-ratio refers to a stream ID, so that shouldn't matter
where it is located in the cmdline. I though that you used
--aspect-ratio 16:9, which will put AR 9 on stream 16.

> 
> > Other unrelated suggestions:
> > - do you really need pullup,softskip,harddup filters?
> > - I would not scale the movie before encoding, but let the reader do this
> > - I think you forgot to remove turbo=1 from 2nd pass cmdline
> > Those are just suggestions, I actually have no clue about what you are
> > doing, so what are your needs.
> >
> >   
> 
> pullup,softskip are used to remove telecined video. mencoder manual
> talks about using this.

OK if your source is telecined.

> 
> harddup is for audio/video sync. I don't know if it it always necessary,
> but I'm afraid to change things that work.

I use this filter only when needed (-of mpeg for instance), and most of
the time, I have no problem with AV sync.

> 
> I want to scale the movie to reduce filesize and to ensure I have a 16:9
> ratio. Do you think this is a bad idea? If so, why?

Going from 720x352 to 640x360 doesn't decrease much the number of
pixels, and would spread the artifacts introduced by the first encoding
(to DVD video), leading to adding more artifacts than if you don't
scale. About the aspect ratio, as it is specified in mkv, or directly in
x264 bitstream using dsize vf as RC told, all readers should resize the
video correctly, often using accelerated scaling.
However, I'm far from being a video guru, and I cannot answer a clear
yes or no, I just would not do scaling here.

> 
> I took all the x264encopts from an article I read on the web. I have no
> idea what any of them are. You're saying I don't need and shouldn't use
> turbo on the second pass?

Read the man mplayer, go to the -x264encopts part (use '/' to search),
and lurk a bit. I think you're not commited to understand everything,
but it gives good terms to search for over the web.
About turbo, it says it is intented for first pass only (or everything
else the last pass).

> 
> --John Ratliff
> 
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