[mythtv-users] Looking for a mainboard

Brad Templeton brad+myth at templetons.com
Tue Mar 1 20:16:55 UTC 2005


On Tue, Mar 01, 2005 at 11:37:51AM -0600, Bryce wrote:
> On Tue, March 1, 2005 11:26 am, Joe Barnhart said:
> Really? I hadn't seen that. I'll have to do some more reading. (Like I
> don't have enough to research about this crazy project already! <grin>). I
> don't really have anything against Intel and usually spec my linux servers
> with dual Xeons. I just hate to pay the premium on Intel cpus for personal
> machines.
> 
> > Oh, and your disk drive is way too small.  HD eats up
> > video at 8G/hour.  Your hard disk won't even hold a
> > week of programs.
> 
> Oh I know, it's just a start. I figure I'll end up with 145-150GB of space
> for video, at 8G/hour that gives me 18 hours of HD storage. I don't have
> cable or anything so everything I grab will be "Network TV" and my wife
> and I watch no where near 18 hours a week of TV. I'll build a nice
> rackmounted backend in the basement sometime later.
> 

Actually, while the current myth transcoding tools are not designed for
dealing with the multiple resolutions that come from HD, I have found
you can transcode 1080i to either 1280x720px30fps or if you like
1280x540 and get a very good, high-def recording in under 2gb per hour.

The trick is that for most HDTVs sold today that are DLP or LCD, the
native resolution is near 1280 x 720.   So you lose no resolution
downscaling like that, and even the 1280x540 is giving you 75% of the
resolution, and allows perfect de-interlacing.

I have been doing my transcoding with manual scripts like this until such
time as the myth transcoder becomes multi-resolution.  That's a hard
challenge though, because there are so many transcoding needs, including:
    a) Drop 1080i to "TV native res" or "TV native width"x540p
    b) Drop 720p to mp4 without loss of resolution
    c) Drop 480p embedded in 1080i to 480p (crop and transcode and deint)
    d) Drop 480p embedded in 720p to 480p  (crop etc.)
    e) Transcode 480i to 352x480i


#!/bin/bash
rate=${2:-3500}
scale=${3:-1280:-2}
#inter=ildct:ilme
inter=""
copts=autoaspect:$inter:mbd=2:v4mv:naq:cmp=3:subcmp=3
p=3
for pass in 1:turbo 2 ; do
    mencoder $1 -vf pp=ci,scale=$scale -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=$rate:$copts:vpass=$pass -oac mp3lame -o out.avi
    done


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