[mythtv-users] VGA to Component adaptors
Cory Papenfuss
papenfuss at juneau.me.vt.edu
Wed Apr 27 11:20:34 UTC 2005
> There is a thread on nvnews about the component out in Linux, but no real
> conclusions yay or nay. Someone here (Cory?) built his own, but I never did
> get all the details. Seemed pretty simple from what I remember.
>
Ooops... I just re-read what I was accused of accomplishing. The
circuit I built converterted RGBHV (i.e. VGA) at 480i frequencies to
*composite* (and s-vid). It wasn't component.
The RGBHV->component is a much easier circuit, though. There are
lots of instructions on the 'net for how to build a transcoder for that.
The toughest part is figuring out which gain matrix is correct for
RGB->YPbPr... there seem to be a few different ones floating about.
Also, one minor caveat that I think most people happily
ignore is that component video is supposed to have bipolar sync signals.
Unlike the TTL-like signals of RGBHV, component sync is supposed to be
nominally zero, go negative for a bit, then posititive for a bit, then
back to zero. It keeps the DC level of the sync signal zero so DC
restoring circuits aren't necessary.
I don't recall any of the DIY transcoders doing that, but they
seem to work all the same.
-Cory
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
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