Video Capture From svideo, higher resolution?

Posted on 2005-04-07
Last Modified: 2008-03-06
I picked up a capture card from frys for like 40$, nothing special but it has svideo in. My idea was to clone my vid card to the svideo out into a seperate computer with the capture card in it. It works, sort of....

The problem is i cant get the ouput to be bigger than 1024x768.  So lets say im playing a game (what i want to capture) @ 1280x1024. The output to trhe other computer will only capture the 1024x768 pixels in the top left. If i want to capture full screen i have to lower the game resolution to 1024x768.

I have tried TONS of settings in ATI controll center with no difference.

Is there ANY way i can capture at a higher resolution than 1024x768?

If no, please explain why.

Thanks guys.
Question by:ZLucas
    LVL 1

    Accepted Solution

    Your definition is a little unclear (or maybe I need some sleep).

    Do you have  PC with resolution set to  1280x1024 --->S-VID out only top left 1024x768 of 1280x1024 showing? Or is this a problem where you think the input to second PC/capture card is cropping image (what do you see  when you view the output on a tv for example?).

    If output of PC is "cropped", I imagine it is because the frame buffer on the video card will only support a max of 1024x768.

    The short answer here is that converting non-interlaced "vga" data to interlaced NTSC video requires that each frame of "vga" be de-interlaced, converted to two frames, and then further processed such that a scan frequency conversion (and line count reduction/scaling) occurs. because you have to store frames,  you need ram - and generally cheap cards have a smaller frame buffer - hence smaller maximum resolution.  At 1280x1024 the card is grabbing as much as it can and filling the frame buffer...


    Author Comment

    oK,  well your answer helped.

    But here is the thing, i have a ati x800 pro w/ 256mb of mem. thats whats outputing anyway.

    As far as input, well its just a capture card so i dont believe it has any mem.  Ill award you the points but do you have any ideas?
    LVL 1

    Expert Comment

    Think of it this way - the ati video card is converting computer graphics screen to TV signal (s-video). The TV signal is a "standard" - as an analog signal it has certain characteristics - so many lines, certain scan frequency etc This s-video signal is designed to be played back on any TV (of correct standard - NTSC, PAL, SECAM etc) - in other words pumped into devices that know what the video standard is.

    Now the capture card is designed to grab each frame of analog video and convert it to computer graphics screen. That means it will digitize the entire video frame all the time (or should - see note below). In other words, the capture card always grabs the same "size" of frame (a standard analog  video frame) then digitizes it, then scales it up or down to fit the VGA card width X height.

    If the capture card is only showing a portion of the screen, that most probably means that the output of your ATI card only supports a maximum resolution, and if you go beyond that resolution it will try and show you *something* by digitizing as big a chunk as possible.

    The easy way to test this is to take the output of the ATI card and plug it into a TV (or record on s-video vcr) - you should see a cropped image.

    The only thing I can think of that might help is to turn off VGA portion. That is, I've had video cards that supported larger resolution output as long as the card didn't have to send graphics to both the VGA  AND the video output at the same time. Game play will be weird, you'll be watching game on capture-card PC in bad resolution.

    Note that I've also used capture cards that let you set a  window within the video input. That is, you could (with software tools) tell the capture card to only digitze a corner of the incoming signal  - but the default was to digitize all - and these cards were more than $40.00 <g>


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