Tearing with scan convertor

We've been having some output problems, everything looks fine on the attached monitors, but the output from the scan convertors has tearing, ie half a frame from one frame half from the next, generally in the middle. We've tried 800x600 and 1024x768, at 60hz and 75hz, were using the corioscan pro's, has anyone seen this, or found a setting on the scannies to minimise it? I've tried flicker removal setting, but I'm wondering if we need to crop lines from the vga or or not.
It's most visible on strobing/fast footage
Cheers


Cat

Unfortunately this can be a problem with scan converters. Make sure that you've got the cleanest signal you can get going into them, so you can eliminate the server from the chain. Sometimes having ferrites on the VGA cable can help with this kind of thing.

I've not used the Corioscans personally, but I've seen this kind of thing with Extron VSC700D's - specifically with 75Hz.

The ulitmate scan converter IMHO is the Barco/Folsom Image Pro HD, which gives a very clean signal.

Hugh

this will probably be due to the fact that the output frequency of the mac is not exactly 75hz or 60hz.

are you genlocking to anything?
turn off genlocking if you have it on.

this will/might be part of the scan convertor design - and its attempt to lock to its own version of 60hz or 75hz.

you will have to try different scan convertors.

you see exactly the same thing with a DL1 -when you run the input at 75Hz.
sure it will take 75Hz in. but internally the device works at 60Hz so you get exactly these problems.

this isnt normally an electrical problem its a design problem in scan convertors.

Quote:

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Originally Posted by Spam Butterfly

The ulitmate scan converter IMHO is the Barco/Folsom Image Pro HD, which gives a very clean signal.

Hugh

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I can tell you that I use the Image Pros on all my shows, and have never had the tearing problem

Jason

the image pro's actually display the correct frequency of the incoming vga or dvi signal.


Image Pro HD's were used on all the shows i did in the last few months.

They are controllable over ethernet. I thought about writing an interface for them.

We're genlocked to the mixer so presumably taking the lock off would be bad?
I think I've some ferrites somewhere, I'll try and find them and check that out too.
Is there anyway of saving the default res of Catalyst, it always defaults to 1024 @ 75hz at the moment, I presume there a settings file somewhere?
Anyway thanks for the replies

Cat

ah. genlocking....
thats whats causing the tearing.
ferrites arent going to help.

see the computer monitor output doesnt run at exactly 75Hz.
its something like 75.02Hz.
dont ask me why, i cant change it.

this means that unless the scan convertor is very clever - and it sounds like this one isnt that clever...you get tearing as the genlock input goes out of sync with the dvi/vga input
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what kindof projection/output system are you using?

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Is there anyway of saving the default res of Catalyst, it always defaults to 1024 @ 75hz at the moment, I presume there a settings file somewhere

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there is a menu item that changes the screen size.
BUT this can really confuse some projectors - particularily barco projectors.

also are you using the CIB to output RGBHV?

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what kindof projection/output system are you using?

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Were going to a vision mixer so they can add some closeup cameras and then to a Barco Led Wall.
75.02
Ahh! You'd think wouldnt you! Sounds like american companies bringing a little bit of NTSC to europe....
Were coming straight out of the scanconvertors I think, I didnt set them up, and there not mine, I'm a newbie with catalyst ( and macs in general! Hears hissing stage right ) :eek:
Thanks for your help, seems theres not a lot we can do, but I'll fiddle when Im in again and see!

Cat

really it depends on the technology in the scan convertors whether they can handle this.

it isnt just macs - this affects pc's as well.
the so called '75hz' output from the boards isnt exactly 75hz.

and its different at different screen sizes.
at 800x600 its different from 1024x768 and different again at 1280x1024.

you will probably have to test different scan convertors to see how they handle this.
i have used folsom image pro hd's on the last few shows- going to barco d320 screen processors using sdi, and they didnt see this. but they are expensive.