[mythtv-users] good quality TV-out question

Florin Andrei florin at andrei.myip.org
Fri Dec 3 00:55:33 UTC 2004


I learned about MythTV long time ago, but it was only yesterday that i
decided to give it a spin. I am thoroughly impressed! This is one piece
of kick-ass software, if there ever was one.

I'm thinking to build a single-purpose machine running MythTV, a TiVo
replacement as it were. My main concern at this time is the TV-out

Here's the problem:

A while back (ok, way back) i bought a GeForce2 card with a TV-out
connector. I must say, i was less than impressed with the image quality
of it. Don't get me wrong, it was not bad, but i'm rather picky when it
comes to image/sound quality. Ok, i'm a HiFi freak actually. :-)
The raster of the original image (in the video file) never matched
perfectly the raster on the TV, hence all interlaced movies got screwed
up. I couldn't seem to ever get the image to match properly the margins
of the TV screen. The geometry was never perfect. The colors were washed
out. The image was a bit noisy.
I came to believe that these are inherent problems with TV-out, but i
could be wrong.

Looking for something better, i discovered DXR3. I bought a DXR3 card
(they're very cheap on eBay), which definitely has much better image
quality on the TV screen. In fact, it's as good as a decent DVD player.
There's an inherent perfect match between the raster of the video file
and the raster of the TV screen (DXR3 is essentially an MPEG1/2 decoder
that only works when fed properly formatted MPEG1/2 streams). No noise i
could detect, no geometry screw-ups, the image is bright and the colors
are good.
However, it has lots of problems, including lack of support from some
media players, driver issues (nasty kernel module things), and then if
the source is not MPEG1/2 the player has to perform conversion on-the-
fly (it's doable, but the libraries that do that are not perfect), etc.

So... What are you guys using to get good image quality from the TV-out

I'm thinking - isn't a MPEG2 hardware encoder supposed to do all that
DXR3 did, and more? Since you encode straight to MPEG2 with that device,
can you play MPEG2 back to it and get the MPEG2 stream translated
directly to analog TV video, without the MPEG2-to-SVGA-to-TV detour
which essentially destroys the image quality when using a classic TV-
(i have no experience whatsoever with MPEG2 hardware encoders)

Florin Andrei


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