[mythtv-users] Re: TV-Out: AITech Scan Converter vs CX2587x

Fred byq1iis02 at sneakemail.com
Thu Sep 11 14:34:11 EDT 2003


I just tried out a GeForce3 with the Conexant CX25871 Rev 1 (1:8A)
connected to my high quality standard definition television (32" Sony
WEGA XBR) using the S-Video connector.

I'm not happy.

I spent hours adjusting the overscan using nvtv (I now fully appreciate
why it's labeled "alpha" software).  I got the screen image to just
barely exceed the television borders (which is what I want).  That
part's okay except for the upper left hand corner.  For some reason the
top left scan line bends downward to the left so the top scan line in
the upper left hand corner is always dark.  The other three corners are
fine.  I tried nudging the overscan to move the corner up a tad but the
overscan modes go in discrete steps and the next one up is more than I
want.

The second problem is two broad arcs of color.  When I'm looking at a
white image, I see what looks like a pink circle about the diameter of
my screen, without the top and bottom arcs.  The arcs are about an inch
thick.

The problems are subtle enough (and NTSC televisions bad enough) that
I'm not surprised the Conexant chip is sold as a reasonable TV-out
solution.  It's just not up to the requirements of my intended
application, which is the sole video source for my TV.

The TVTool people compared Philips, Chrontel, Conexant, and Brooktree TV
encoder chips [1] and rated the CX25871 as the best.  For this reason
I'm giving up on encoder chips and will look next at scan converters. 
I'm apprehensive about losing interlaced capability but the
(proprietary) nVidia driver's messages made me think it doesn't allow
interlaced output either.

Fred

[1] http://tvtool.info/english/tvchips_e.htm




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