[mythtv-users] PVR-350 clarification

etienne.sandre at polytechnique.org etienne.sandre at polytechnique.org
Fri Jun 17 08:47:08 UTC 2005

> And then either way, is the quality of playback with the PVR-350 and its
> MPEG-1/2 decoder something I can't find in a video card's TV-OUT?  Unless
> its too expensive, I'd assume not.  In which case would it then be best to
> play all video regardless through one output?

Yes, there is something you can't find.
If you watch interlaced shows, you will get the best quality by keeping
the video interlaced up to the TV. By deinterlacing, you loose vertical
resolution and you reduce the smoothness of the animation (you have 25fps
instead of 50fps in PAL, 30fps/60fps in NTSC).
It is not impossible to keep interlacing on a video card tv out. It
requires to store all records in the native vertical resolution (576 lines
in PAL), and to set the video card AND the mythtv window TVout to this
exact resolution, with full overscan. The mythtv overscan has to be set to
0. You also have to deactivate the flickerfilter of your video card (which
does something similar to blend deinterlacing). This is quite tricky to
get all this working on some video cards, and you still get some
smoothness issues due to vsync problems (I've never successfully set my
Geforce2MX vertical refresh frequency to 50Hz, which is the PAL
frequency). Then you cannot reduce the vertical resolution of your
recorded shows without deinterlacing. And your GUI flickers a lot.
Also, many video cards tvouts does filter the image before output, to give
a better render of desktops and windows, but are not well suited for

With the PVR350 decoder, interlaced shows are perfectly rendered, at all
resolutions, and the flickerfilter affects only the framebuffer, ie the
GUI, and does not affect the video.
The PVR 350 tvout is not more complex and more expensive than on video
cards, but only more adapted to display tv signals with GUI layer above.
You will get better quality with much less pain.

> I guess what I'm also asking is that if I do want the most versatility for
> the future (newer codecs, eventually DVD playback, other myth front ends,
> and whatever else who knows) would I be limiting myself if I used a
> PVR-350
> as my only TV-out.

This is true : it is not yet possible to watch properly divx, dvd and
other stuffs on the pvr350 tvout.

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