You are totally right. I have all my computers are in a rack in the kitchen and all my video stuff in the living room. I figured out that if I string a video wire from one room to the other, I get the artifacts. If everything stays in the same room, everything is fine. BTW: Each room is on a diff. circuit, and the wiring in this apt. sucks. Also, my servers all run on UPS, so that might have something to do with it. If anyone is interested, I will make some pictures and put up a little page on how to modify the tuners on cheap bt848 cards. --Tom ----- Original Message ----- From: "Steve Tell" <tell@xxxxxxxxxxxxxxx> To: <video4linux-list@xxxxxxxxxx> Cc: "Thomas Hargrove" <ciagon@xxxxxxxxxxxxxxx> Sent: Saturday, May 12, 2001 6:40 PM Subject: Re: Getting composite out on a bt848 > On Sat, 12 May 2001, Thomas Hargrove wrote: > > > Well, incase anyone is interested, I have been working on a way to get > > composite out on cheap bt848 based cards. I found the correct pin on the > > tuner, and connected a rca cable to it and to a ground. > > Sounds like fun! > > > (BTW: I got the specs from someone on this list. They are here: > > ftp://telepresence.dmem.strath.ac.uk/pub/bt848/spec) > > > > Right now, I have a good signal except for one thing. I get a faint light > > bar that moves slowly up the screen. Other than that, there is no noise. > > If your video is NTSC and your AC power is 60 Hz, this sounds exactly like > what 60Hz hum beating against the 59.94Hz vertical scan rate looks like. > > I'd verify that by looking at your new video output with an osciloscope. > > First, make sure that your composite video monitor's grounded power cord > is connected to the same power strip as the computer. > > Then consider where you're connecting the new connector's "ground" on the > board, and try moving the connection. If the board seperates analog and > digital ground, use analog ground. In this cas AGND and DGND will be > connected together somewhere on the board, but otherwise they need to be > kept seperate. The Bt879 datasheet says that it is possible to build > boards either way. Keeping analog video signals clean in the high-speed > digital environment of a PCI card can be tricky. > > > I was wondering it this is interference with the capture chipset and my TV. > > I think I might disconnect the pin from the board, but that will pernanitely > > damage the card. Can anyone tell me if that might solve my problem? > > Hmmm, probably not. Maybe it would be easier to temporarily break the > connection somewhere nearer to the tuner? > > I'm am a bit surprised that you can connect another video load in parallel > with the capture chip and get decent video without a buffer of some > kind. You are probably double-terminating the tuner output; there should > be a 75-ohm termination resistor near the BT chip input, and the composite > output adds a second one, probably cutting the video signal level in half > and relying on the AGC circuits to fix things up. > > Anyway, I'm interested in corresponding on this and other analog video > hacks. > > Just curious, what card are you using? I'm having no success making > v4l/bttv work at all with a Hauppage "WinTV Go" card which is one of the > cheaper cards available these days. > > Steve > > -- > Steve Tell tell@xxxxxxxxxxxxxxx > > > > > > _______________________________________________ > Video4linux-list mailing list > Video4linux-list@xxxxxxxxxx > https://listman.redhat.com/mailman/listinfo/video4linux-list >
