Post by thread:Video injection

Hi to all I know this is a topic that has been discussed before but I'd appreciate if anyone can share some idea's for a quick and not too dirty (and cost effective) solution to this one. I need to superimpose a timer on a television screen( the original images must still be visible )... the bottom portion of the screen is ok. The source of the time will be a PC. I was thinking on the lines of using a PIC to modulate one of those little UHF units found in tv games, getting the timer count from a PC. ....or bit banging the LPT to modulate the UHF module if possible and then mixing the signals??? To tell the truth, I haven't the foggiest of how to go about this.... Something like this \ / \ / ( ) +-------------------+ | /---------------\ | | | | | | | | | | | | | | | | | | |_______________| | | | 00:00:00 | | | \---------------/ | +-------------------+ // \\ Any ideas?? Regards Jacques Vrey Iscor Profile Products Post Point 74 PO Box 2 Newcastle South Africa 2940 TEL:+27 (0)3431 48759 FAX:+27 (0)3431 48001 spam_OUTjvreyTakeThisOuTit.new.iscorltd.co.za The views expressed above are not necessarily those of Iscor Limited.

<Jacques Vrey Writes> I know this is a topic that has been discussed before but I'd appreciate if anyone can share some idea's for a quick and not too dirty (and cost effective) solution to this one. I need to superimpose a timer on a television screen( the original images must still be visible )... the bottom portion of the screen is ok. The source of the time will be a PC. I was thinking on the lines of using a PIC to modulate one of those little UHF units found in tv games, getting the timer count from a PC. ....or bit banging the LPT to modulate the UHF module if possible and then mixing the signals??? Something like this \ / \ / ( ) +-------------------+ | /-----------------\ | | | | | | | | | | | | | | | | | | |__________| | | | 00:00:00 | | | \-----------------/ | +-------------------+ // \\ Any ideas?? <Win responds> Hi Jacques, Best bet is an OSD (on screen display) chip. One suggestion is the Zilog Z8612912 (PSC is 18 pin skinny DIP, DDC is 20 pin SOIC) which sells in the US$2 to US$3 range. It pretty much takes care of everything and hangs on the I2C bus if I recall correctly. What I don't know is if it will generate the classic time code scroll, but I gather from your ASCII art that you aren't planning to show frames so this shouldn't be a problem. Zilog is a bit flaky about this part (a closed caption decoder for NTSC and PAL) probably because they didn't design it (it shows so watch for odd little undocumented die changes), but if you stick to the core functions which include OSD you should be OK. Cheers, Win Wiencke Image Logic Corporation

many years ago I designed and built just this. You must have a video signal and decode the horizontal and verticle sync. There are several clock chips out there that interface to tv signals, I suppose a pic would do if you want to. After you have mixed the clock signal with the video signal, then you could use a modulator to see it via a tv channel. Andy MacDonald {Original Message removed}

Hello Andy, after reading this mail : {Quote hidden}> many years ago I designed and built just this. You must have a video > signal and decode the horizontal and verticle sync. There are several > clock chips out there that interface to tv signals, I suppose a pic > would do if you want to. After you have mixed the clock signal with > the video signal, then you could use a modulator to see it via a tv > channel. > > > Andy MacDonald I've got the following question, could you put your results, schematics or software onto the list so that we can all learn from it. I'm perhaps not the only one who is interrseted in OSD-signals (well the hardware to be exact). (JPEG or GIF could be a readable standard for everyone) Happy PIC-ing, J. Derogee

Normally one mixes the signals in the video (baseband) signal, using a module that does this, for example the one that was advertised on this list a few days ago. If I understand well, you want to superimpose the clock such that the signals mix on air ? This is also possible, but it requires some amount of trickery. I have done such a thing once. What you need is a complete receiver for the signal being received, to be able to separate the sync pulses from it, to drive a character generator, and a small transmitter that sends only the character data (no sync) on the same frequency as the channel being received. Since you can't lower the signal on air (can't vector mix because not phase locked with the image), you have to send something approximating white noise in the high video freq. range as video signal, keyed by the character output. I used a white noise generator and a slight peaking filter that peaks at 5 MHz or so. Forget about passing color. The white noise modulation makes the characters apparent even if the image is bright white under them. If the FCC or whoever catches you doing this over the air, we'll send you sweets when you're in jail ;). Note that a normal VCR modulator is amply sufficient to superimpose on a local station like this, over 3-5 meters (both sets use 'stick' pull-out antennas). Peter