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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.


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 Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *

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