[mythtv-users] commercially-produced mythboxes -- an idea

[Brad Templeton]

On Thu, Jan 13, 2005 at 08:56:27AM -0700, Brandon Beattie wrote:
> XvMC only doesn't work if you seek.  Also, it still takes about a 2ghz
> system for displaying the video *only* if you're transcoding... read
> below..

Well, if by seek you mean jump to other parts of the show with skip-ahead
or commercial skip, that's a big "only if" -- to me this is a big part
of what PVRs are about.
>  
> 1280x720 takes about a 1.9 ghz system.  You also only would save a
> slight bit of space because you would only be transcoding 1080i, which
> would be a pro since you would not be de-interlacing in real time.  A

Hmm.  My own tests showed saving a fair bit more than that.  One reason
is that mp4 is smaller than mp2 at the same quality.   You might also
be transcoding your 1080i down to 30fps, which is still better than
movie speed, though perhaps you would want your sports to stay at 60fps,
but you definitely need to deinterlace.

Of course the more artifacts you want to tolerate, the more you can
drop the quality on an mp4, and get a lot more recordings on your disk.

 con though is myth isn't smart enough yet to transcode to different

Right, though I had always presumed that the more folks worked with
HDTV, the more aware it will become of dealing with different resolutions,
aspect ratios and frame rates.  If there's a handy attribute extractor
out there, it would actually be pretty easy for me to write a smart transcoder
that queries the videos and changes the rules it feeds to mencoder based
on their parameters as an independent script.  (And presumably not too
hard to eventually integrate it into myth.)

> If you're transcoding, you're using a LOT of cpu, and so you can't watch
> HD and transcode at the same time with good results on a slower PC.  It
> takes about 3.5x as long to transcode HD to 1024x576 in my tests (amd
> 2500) as the shows running length.  This means if you have a slower
> system and record just 4-6 shows a day your system may be maxed out
> 24/7.

Yes, this would be a call for having another CPU to do the work.  And
while not present in the design for a pre-built box above, I have always
been fond of the remote frontend approach which fortunately would be
able to do that.  Of course that's expensive -- unless, like many of us,
you already have a server machine that's up all the time to use as backend,
and are buying/building only the frontend box.