Maybe you can get your hands on a used video toaster --a card from a company called NewTek that went into the old Amiga 2000, 3000's that handled most of those video functions. I always wanted one when I was into Amiga's, but maybe you can find one cheap now that they're over 10 years old (geez thats depressing.) -Dal ----- Original Message ----- From: Robert Rolf To: Sent: Tuesday, June 19, 2001 6:41 PM Subject: Re: [OT]:Video Mixing with Keyed Overlay > Good advice Ashley. > > The quick and dirty way to do what David wants is to put an > ATI 'All-in-Wonder' card into his machine ($180C). The AIW cards > digitize > the incoming video and put it into a variable sized window (including > full screen, even at 1280x1024) for display on your monitor. It also > has a TV out capability (S and composite), so you'd set > your screen to 640x480 resolution > (to match that of your incoming video) and then make the video your > desktop, with whatever graphics you want on top. > > They have a SDK for their API so writing your own C app to drive > the card is not too hard. > > The AIW cards do ALL the work on-board (by default they use Magenta > to key in the video) so the video stream happily continues even when > your box locks up. > > Now if you really want to MIX the signals (as in variable transparency), > the ATI card won't do it since it's strickly a background keyer. > > You might also want to look as some of the older Elsa cards. > Their 'Gloria Synergy' card can output any single desktop window > as video, so concievably you could get your video into your system > via any video digitizer, then use the Elsa to output that window, > with graphics overlay, as video. > > And then there is the DPS product line of 'personal time base > correctors'. They would allow you to retime your incoming > video to that of your computer, where you can then build a > simple analog mixer to combine them. > > Do remember that the bandwidth of NTSC/PAl video is a fraction > of what you have for your desktop (200 line pairs vs the 400 of > a common 800x600 screen) so your graphics have to be constructed > -specifically- for video output. > > For more discussion, contact me off-list. I do a fair bit of > computer video in my 'other life'. > > Ashley Roll wrote: > > > > Hi David, > > > > I'm no expert in this, but from what I know your going to have a few > > problems with a "mixer". > > > > You would have to ensure that the two video signals are synchronised (called > > "locked" in the video industry I think - you use equipment that supports > > external "gen-lock") so that when you mix the signals you get the correct > > bit of it and the timing isn't disturbed causing the image to rip apart.. > > Basically this is difficult. If your very lucky you video source may have a > > gen-lock input so you could derive a lock signal from your computer video to > > lock them together.. > > > > How complex are the graphics? On screen displays are normally done by > > arranging a switch in the video signal and switches between the real signal > > and a specific colour level (voltage) at the right time in the video > > frame/field/scan line. You could possibly use a PIC or SX to do this :) Look > > at http://www.piclist.com/techref/scenix/lib/io/dev/video/index.htm for some > > ideas. > > > > These actually generate the entire signal, but you would just switch between > > the live video and your set voltage representing a colour. (if you get > > really tricky that voltage could be generated from your PIC to give you > > several colours) > > > > There are also on-screen display chips that do this all for you.. > > > > The "big boys" now all edit digitally, you digitise the video for your > > entire movie (at movie resolution of at least 4096x3072 for "low res") to a > > big disk array, mess with it with some expensive software and send it our > > again.. it is possible to do this is real time, but not cheap.. not cheap at > > all.. > > > > Some "home" video capture cards should let you do what you want also which > > would be a lot cheaper :) You should be able to have them overlay video into > > a "keyed" area of your display and you can take the TV out and record it. > > All the "gen-locking" is done by digitising the video and copying pixels > > normally. > > > > Good Luck. > > Ash. > > > > > I am trying to find a circuit or device that would allow me > > > to mix baseband > > > video from my computer (Already has TV Out) with a 2nd video > > > source. I am > > > trying to do Graphics On Screen Display (with existing video in > > > background), so Keyed Overlay support is needed. > > > > > > I have found a few scan converters that take VGA and offer > > > Keyed Overlay > > > onto a video source, but tend to be too expensive ($500 - $3000). > > > > > > I am hoping to find a simple circuit I can build (good at > > > building, bad at > > > designing), or even a cheap (<=$200) unit I could purchase, > > > that would do > > > good quality keyed video mixing. (No need for broadcast quality). > > > > > > Any help would be appreciated. > > > > > > David. > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu