[mythtv-users] Tutorial on Encoding (mostly re: file sizes)

Robert Tsai rtsai1111 at comcast.net
Tue Sep 20 20:38:55 UTC 2005

On Tue, Sep 20, 2005 at 03:58:22PM -0400, Brian McEntire wrote:
> When resizing, is it possible to accidentally stretch the image?
> I saw someone say 480x480 wouldn't be a noticeable difference from
> 720x480... is the because of the way a TV uses scan lines? On a
> monitor it seems like it would be very different.
> I'm curious because I want to transcode HDTV (1920x1080, 1280x720,
> and 850x480) down to 850x480.
> For HDTV pulled off of QAM/Cable, I'm seeing MPEG2 file sizes of
> about 6.2GB/hr.

I've been transcoding my HD-3000-captured HDTV recordings down to
856x480 at 4400kbps (bitrate scaled to 640x480), for about 1.8GB/hr.
It looks fine.

My "Medium Quality" stuff is at 720x480 at 3300kbps (bitrate scaled
from 640x480), and it also looks fine.

I've been playing around with "Low Quality", currently at 640x480 at
2200kbps, and it also looks fine, for a little over 1GB/hr. I've been
ratcheting it lower and lower.

There is visible difference between the three resolution/bitrate
settings (more blocking, etc.), but everything is still very watchable
on a 42" RPTV.

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