[mythtv-users] Convert nuv to mpg

[Scott Alfter]

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Andrew Robinson wrote:
> Does anyone have an example or a pointer to an example of a 'transcode' 
> command to convert a nuv file to an mpg file?

I use mencoder (part of mplayer) for audio and video encoding.  Something like
this would work:

#!/bin/sh
src=$1
dest=$2
vbitrate=$3
nice -n 18 mencoder -vf pullup,softskip,scale=720:480,harddup -ofps 24000/1001
- -ovc lavc -lavcopts
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9600:vbitrate=${vbitrate}:keyint=18:vpass=1:turbo:trell:dc=10
- -oac copy -o /dev/null ${src}
nice -n 18 mencoder -vf pullup,softskip,scale=720:480,harddup -ofps 24000/1001
- -ovc lavc -lavcopts
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9600:vbitrate=${vbitrate}:keyint=18:vpass=2:turbo:trell:dc=10
- -oac lavc -lavcopts acodec=ac3:abitrate=192 -of mpeg -o ${dest} ${src}

(This script should have six lines.  "nice -n 18 mencoder..." starts the last
two lines.)

As given above, this will scale to 720x480, do inverse 3:2 pulldown (which is
appropriate for most TV shows, but may not be so good for news, sports, or
other live events), and does two-pass VBR encoding of film-rate NTSC at 4.2
Mbps.  In addition, it transcodes the audio to AC3 at 192 kbps.  Change the
vbitrate parameter to adjust the video bitrate.

Interlaced encoding of news/sports/etc. requires some changes.  Leave out
"pullup,softskip" from the video filter (-vf) options, change the framerate
(-ofps) from 24000/1001 fps to 30000/1001 fps, and add "ilme,ildct" to the
video encoder options (the first -lavcopts in each command).

Lots of shows are broadcast in letterbox format.  You might want to convert
these to widescreen; the encoder might have an easier time without the black
bars at top and bottom.  To do that, insert "crop=480:360:0:60" before the
scale filter in the filter options, and add "aspect=16/9" to the video encoder
options.  (This assumes that your source video is encoded at 480x480; adjust
the first number if it isn't.)

  _/_
 / v \ Scott Alfter
(IIGS( http://alfter.us/            Top-posting!
 \_^_/ rm -rf /bin/laden            >What's the most annoying thing on Usenet?

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