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  • Matrox Capture Capabilities

    I have been doing some research on “broadcast quality” and realised I have always misunderstood the concepts of lines of resolution, camera resolution and broadcast resolution.

    For some reason I assumed that the 500 lines of resolution of the DV standard referred to the image in terms of pixels (and I assumed the same was true for VHS/S-VHS etc). Probably the “Digital” word confused me, so I thought it was actually a “picture” made up of 500 lines. I now know that if refers to the resolution of the image and its ability to “view” and accurately represent 500 lines in the image it is pointed at! (i.e. a 400 line resolution camera would see a blur if looking at the fine detail of 500 lines on a page for example and a 500 line or better camera would produce an image where you could distinguish the 500 lines).

    Now my Matrox capture card (G200) is capable of capturing an image that is 704 pixels by 576 pixels. Because of the price when I bought it I always assumed the Matrox card was a bit of a “toy” not capable of capturing as high as “broadcast quality”. However I am now wondering if is really only limited by the quality of the camera or playback device?

    From this conclusion I have made the leap in logic that the quality of the captured video is solely dependant on the quality of the image the camera provides. So in theory if I was to plug in a Betacam SP camera or VCR into the S-video input (assuming Betacam’s have an S-video output? I can’t say I’ve ever used one) and capture uncompressed YUV or similar it would be capable of capturing “broadcast quality” images.

    Am I dreaming or is this accurate. I realise there are some other considerations regarding audio and component quality is better etc in the “broadcast quality” debate.

    Some comments from the experts would be appreciated.

  • #2
    You are right in the fact that better input quality leads to better capture quality, but you would be limited by the actual hardware portion of the card. There aren't a whole lot of components on there, so the image would be better, but not comparable to say an AVID or something similar. I have hooked up a signal generator to mine (only composite though) and it did look pretty impressive, but your actual resolution (doing a frequency response) it tends to muddy out a little sooner than a high end machine. This is the area that the price does make a difference, also in the color (4:2:0, 4:2:2, etc..) You just can't pack the filters and such into a card that size.

    For the price though, nothing comes close in my opinion.
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    • #3
      I agree the G200 gives good quality capture from a clean source. On the subject of resolution, when the lines of resolution are quoted for TV, Video, DV, DVD etc they are talking about horizontal res, ie vertical lines. It is the number of vertical black and white bars that can be resolved along the (fixed number of) horizontal scan lines.

      So if you see 250 quoted for SVHS for instance, it doesn' t matter how many horizontal lines you have, it indicates how many repeating vertical bars you can make out before it muzzes out.

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      • #4
        I'm Impressed!

        I think I lucked in as far as value for money goes when I bought the Matrox G200. Pretty impressive really. I allways was impressed with the quality I was getting from the composite input and MJPEG. But I've recently been using S-VHS and have been more impressed.

        I would prefer w2k as an o/s but if the next step up is an Avid (or similar) system then you can't complain really. I think most don't relaise what they really have. The input and output of the G200/400 is worth putting up with win98 unless you have spare $10,000's (and plenty of them!).

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        • #5
          I think the important point to remember is that an ordinary TV set has a horizontal resolution equivalent to 250-300 lines. Your Marvel G-200 is 704 pixels wide, so this can theoretically resolve 352 equivalent lines (alternate pixels black and white), so it is better than a TV set (as opposed to a pro monitor). If what you are doing is destined to be viewed on a TV set, then the result will be fine.

          That having been said, the better the quality of the analogue input, the better the results. A given pixel will decide its luma and chroma intensities according to the signal and that particular point of a scan. If the image is fuzzy, then, instead of sharply delineating the edge of the lapel of someone's dinner jacket (tux for you guys across the Atlantic ) against his white shirt, it will put in a few consecutive grey pixels of increasing intensity, which will blur together even more on a TV. If the incoming image is really sharp, then one pixel will be black and the next white, with possibly one intermediate if it falls where the analogue signal is dropping. On a hi-res monitor, you may see this as a staircase, if you look closely, but on a TV it will look sharper than in the first case but you will never see the staircase.

          Moral: the better the incoming image, the better the results, even if a TV has a lower resolution.
          Brian (the devil incarnate)

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