Re: [MEncoder-users] PAL -> NTSC

On Tue, 27 May 2008, Martin wrote:

> I have an interlaced PAL AVI captured from a DV source and want to
> convert it to an interlaced NTSC AVI.

> mencoder file.avi -ovc raw -vf scale=720:480:1 -field-dominance 1 -ofps
> 30000/1001 -oac pcm -o file_ntsc.avi

I believe that should work, but it's less than ideal. You really need a
field-based pulldown (2:2:3:2:3 comes to mind for PAL->NTSC, but don't
quote me). Unfortunately, mencoder doesn't have a generic pulldown
filter, but if you use the MPEG muxer you might try -mpegopts
tele_src=25,tele_dest=30000/1001.

I wouldn't bother with any framerate changes with an intermediate raw
stream, though, since it just takes up extra space (and it really
shouldn't be necessary unless you need to manipulate the video somehow).

In fact, I'd work with the video and audio separately, provided there's no
timestamp wierdness.

> Do I have to change the pixel aspect ratio, and if so, how do i do that
> in mencoder?

The correct aspect ratio should be specified, either via the video stream
or the container, as appropriate, especially as it will be lost with raw
video unless you use -force-avi-aspect (an option which, BTW, should only
be used for files you'll be playing back exclusively with mplayer or
mencoder since hardly anyone recognizes vprp chunks).

For lavc and MPEG 2/4 video, you'd use -lavcopts aspect=4/3 (or 16/9), or
-lavcopts autoaspect if the aspect ratio is encoded in the source (and is
what you want).

With H.264, the aspect ratio has to be supplied by the container.
Matroska uses frame dimensions and mp4 a pixel aspect ratio. I use
mkvmerge and mp4box, so I can't help you with mencoder options there.

YMMV where other coders/containers are concerned.
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