Ext. Sync for Video out?

[snn47]

Does any one happen to know if any of the Matrox chips allow for external synchronisation by applying an external (video)-video-signal?

I want to avoid the black bars rolling down from top to bottem when i use a video-cam for taking a video while having a TV screen in it.

TV-studios have for this a master-sync signal that is the reference for all equipment in the studio (e.g. cam, monitor). What's not in sync like external feeds get's shifted until H/V is in sync again.

I tryed search but couldn't fin any answer.

[Kruzin]

Your question would have a much better chance of being answered in the Desktop Video form, so I will move it over there...

good luck

[snn47]

Thank you,
I thought it's a function of the chipset (if supported/available) it should have been placed IMSO correctly in Hardware?

[Brian Ellis]

I don't think what you ask is possible, but many aeons ago I more or less overcame the problem by a) changing the screen refresh rate to a multiple of the frame frequency (in my case 75 fps refresh for 25 fps). As you may be in a NTSC region, you would have to use either 2 or 3 x 29.9xxx, whatever it is. and b) make sure your camera shutter speed is set to the slowest possible. This minimised strobing for quite long periods, even though it is not positively synched. You may need one or two starts if you wish to eliminate the synch blanking altogether, as it would be luck whether you hit it acceptably or not.

[snn47]

Thank you, I live in "the where 50Hz PAL was designed", I just forgot to add my location.

I could manipulate/slow the clock generation for the card until H/V are in sync, but it's about as much work/dangerous as adding the external sync to my Hi8 cam.

But if it would be possible to time a refresh, it could serve the same purpose.

But I'am still hoping Mac. M has implemented it, but not told us so far (just hoping )

[Sciascia]

OK, after reading the question several times and trying to figure out what you meant (just woke up here ) I know exactly what you mean. Syncing the TV to the camera is not going to make a reliable fix for your problem. The refresh rate is a good suggetion, but it is still a real hit or miss thing. The only reliable way to do it is to adjust your shutter speed on the camera. It is not an option on all cameras so it may not be possible, but if you do have it then it should fix you right up.

[snn47]

Thank you for the reply but that is my assumption:

if the card starts by generating the new picture every 4 "Halbbilder" (=half-picctures meaning odd- or even-lines only while a full-pictures means all lines, please give me the correct words) it should work. At worst I have to use a LM1881 to strip the H-Clk and use it to synchronise the card clock with it.

But since PAL allows us to make inserts of still pictures every 4 "Halbbilder" without beeing able to detect a slight movement from previous to inserted pictures I assume it should work.

Only question how to do it without having to design a complicated "sync PLL" that would take some time to get a lock.


PS. Can you propose a better/easier to understand phrasing for my question?

[snn47]

Just got some info/reply to share

http://forum.matrox.com/mgaforum/Forum8/HTML/001103.html

[QUOTE]Yes it's possible. We have an input called VidRST that allows us to lock onto an external source but the driver has to be aware of it. I don't know if it is and if it is, you have to find a way to lock into to it.
Either way, the 1st thing you have to find out from our developer relations people (devrel@matrox.com) is to see if the driver is aware of this input. If it's not, then unfortunately, you'll have to look at other means on acheiving this.

------------------
Haig
Matrox Graphics
Technical Support Manager

QUOTE]

Now I have to wait until next week.