[mythtv] Ray - Questions about your setup

Ray mythtv-dev@snowman.net
Mon, 9 Dec 2002 11:08:32 -0700

On Sun, Dec 08, 2002 at 11:11:42PM -0800, kevin thayer wrote:
> My goal is to have as hi-res as possible without
> losing the ability to pause/rewind/etc live tv. I
> don't really need a tuner since I have digital cable
> and i'll be controlling it from the mythtv box, using
> direct out.

> Questions I have... (thanks in advance!)
> 1) MythTV supports hardware MJPEG now, right? 
> 1a) and works with the G200's hardware also, yes?

Yes & Yes.

> 2) Does the G200 decode and encode mjpeg at same time
> (in hardware)?
> 2a) If not, can the SMP celeron 500 playback MJPEG
> without jitters whilst recording using hardware?
> 2b) What is the max resolution you can play back MJPEG
> in software (idle PC and while recording)

At the moment I'm using decimation 2 which basically equates to 352x240.  At
dec 1 (720x480) my machine can't decode fast enough.  Actually decimation 2
looks a LOT better than capturing at 352x240 with software encoding and
looks as good or better than VHS on my TV.  I'm planning on swapping this
box with a spare Duron 650 + MB that I have laying around and then upgrade
the cpu later.  

> 3) Did you get your TV-out working with the better
> solution (ie non-framebuffer?)

I am still using the matroxfb stuff but I'm not sure why it would be better
if I didn't use it?  Remember the matroxfb is NOT the same as vesafb and
takes better advantage of the hardware.  Thanks to one of the other posters
here I now have a good modeline for TV-out at 800x600 resolution.  Getting
TV-out working well was a PITA though so buying an external converter might
not be a bad idea.  Also most of the matroxfb developers seem to have G400
series cards so I think there would be less chance of the driver breaking
for those.

> 4) Any comments on controlling external equipment for
> recording? ie digital cable box. Tips/problems/etc...

I'm using directv with an older RCA reciever.  I'm planning on adding a
second receiver+lnb+capture card eventually.  Since capture only takes maybe
10-20% cpu on this setup I shouldn't have any speed problems.  I'm using a
slightly modified script found on the net (see the archives) to change
channels and a homebrew script to grab the local/network channels since
Zap2it/xmltv don't have these.

> 5) How watchable is the software/software record while
> playing back? 352x240 sounds bad :)

It's really quite good.  With decimation it's not really just grabbing at
352x240.  If I understand correctly NTSC is really (almost) 60fps interlaced
so each frame only contains every other vertical line.  What it's really
doing is to grab at 352x480 on every other interlaced frame (called "time
decimation").  I've been meaning to experiment with tweaking these settings
a bit in the source so I could try 720x240 and 352x480 but it looks good
enough (I only have a 19" TV right now) that I've had other priorities.