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Re: [Discuss-gnuradio] Comb Filter (OT tangent)
From: |
Cory Papenfuss |
Subject: |
Re: [Discuss-gnuradio] Comb Filter (OT tangent) |
Date: |
Thu, 6 Jan 2005 07:45:59 -0500 (EST) |
On Wed, 5 Jan 2005, Dave Dodge wrote:
I don't know much about the signal-level details, but some things that
immediately come to mind:
- since (if I understand this correctly) you're talking about using an
RGB framebuffer and the RGB signal lines to generate YPrPb signals,
are the RGB voltage ranges going to be what you need?
I believe the video signal levels are the same 0.7v. I doubt that
the RGB could do "blacker-than-black" except with the sync pulse, but it's
not really necessary for regular video.
- it would most likely work for progressive scan. Do you also need
the interlaced component formats?
Both will work... I've already cooked up modelines to generate
NTSC-spec frequencies interlaced. I've even done sync-on-green and used
that for a monochrome signal on a TV's Y-component and it worked fine.
Pretty phsycho colors if you connect the other two to R and B... :)
There are some simple circuit designs floating around for DIY
RGB->component converters, so you could probably figure out
from those whether the signal itself will present any problems.
http://www.epanorama.net/links/videocircuits.html#rgbyuv
Thanks... I've already seen that and built one. I've even built
one that will generate composite/s-vid. It works, but it'd be nice to not
even have to build hardware for it. This is of particular value to people
on the mythtv list I subscribe to looking for cheap, high-quality tvout of
their HTPC. It's silly to spend money on a good video card that will to
XVideo well ($50-100), and then spend more good money ($100) on a
transcoder. The XVideo is necessary to do YUV->RGB, and the transcoder
does RGB->YCrCb. If the vid card is just three fast DACs, why bother
converting and unconverting for a single-use settop system such as mythtv?
-Cory
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************