[mythtv-users] TV out card suggestions
Michael T. Dean
mtdean at thirdcontact.com
Fri May 7 12:27:04 EDT 2004
Ben Rometsch wrote:
> I'd also be interested to know what the quality of the image is like
> when compared to using the direct TV-Out from a standard video card...?
Read this thread
http://www.gossamer-threads.com/lists/mythtv/users/50643 (updated for
the new archive--the old link didn't work for it).
Basically, it discusses using a VGA to NTSC/PAL converter and the fact
that many video cards use a very low quality converter for their
on-board converter. That coupled with the fact that the on-board
converter has to perform other conversions (color, interlacing, timings,
etc.) tend to cause the display quality to be lower than can be achieved
by using a "good" converter fed a "proper" TV-like signal (i.e. for
NTSC, 29.97Hz interlaced signal). With a proper signal, the converter
simply does a color conversion (RGB to Y/C NTSC). However, the VGA
signal cannot be output to a monitor, but provides very high quality TV
output. This would seem to explain why all TV output I've ever seen
through a VGA to NTSC converter was very low quality--the converter was
required to do far too many conversions because it wasn't driven with a
The only thing that wasn't discussed was the definition of a "good"
I'm building a converter based on the Analog Digital AD724 chip (which
is available from http://www.arrow.com/ and http://www.newark.com/ ).
The design I'm using is the one for the evaluation board (
). If you're not into buiding electronics, you can even buy a completed
board ( search for AD724EB at http://www.arrow.com/ ). The only problem
is that it's about $172US.
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