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PC to TV converter - Video quality is bad!

  1. Oct 7, 2011 #1
    Hi there,

    I am using a PC to TV converter fairly unconventionally. I'm connecting a VGA output to a PC to TV converter. This converter outputs a composite video which I then connect to a USB Video Capture Device, which feeds into my computer . The resolution of the image I want to capture is 640 x 480.

    The PC to TV converter supports
    Resolution (Vertical frequency (Hz):
    PC Compatible VGA mode
    640 X 480 - 60,70,72, 75,85,100,120
    800 X 600 - 56,60,70 ,72,75,85,100
    1024 X768 - 60,70,72, 75

    and the USB Video Capture Device goes up to 720 x 480.

    Basically im going from VGA to Composite to USB, and the display that I get out is blurry/fuzzy, and definitely not 640 x 480 even though the devices support that.

    Does anyone know why this is happening and if I can do anything about it?

    Thanks in Advance!

  2. jcsd
  3. Oct 7, 2011 #2
    My first step would be isolating each piece to see if any one of them was causing the majority of quality loss. Hook the VGA to composite up to a regular TV and see what the picture looks like. Then, hook up a DVD player to the USB capture card and see what quality you get with it.
  4. Oct 7, 2011 #3
  5. Oct 7, 2011 #4
    Thanks for the suggestions. I'll look into it.
  6. Oct 8, 2011 #5
    Those multiple conversions are adding plenty of noise, so make sure you're using shielded cables.

    It would be better to eliminate the VGA -> Composite, and just go VGA -> USB.
  7. Oct 8, 2011 #6


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    Homework Helper

    One issue with NTSC standard def composite at 720x480 is its pixel aspect ratio of .9 to 1, versus VGA's 640x480 pixel aspect ratio which is 1 to 1, both with the same 4:3 screen size ratio. A conversion either way results in a lot of dithering of pixels (destination pixels will be a mix of colors from source pixels).
  8. Oct 11, 2011 #7
    I totally agree, but the VGA to USB capture devices run me 300 bucks :|

    is it the colouring that will be the only issue? I see the colour offset, but my major problem is the resolution. What you've said about the discrepancies between pixel aspect ratios makes sense as to the cause of my issues. They just can't translate properly right?
  9. Oct 11, 2011 #8


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    Homework Helper

    Yes, between the two formats, you're rarely on a common pixel boundary. Every 10th pixel boundary at 720 x 0.9 will correspond to a 9th pixel boundary at 640 x 1.0. All the pixels between these boundaries are some mix of a pair of pixels, so they end up fuzzy.
  10. Oct 12, 2011 #9
    I'm still not clear on exactly what you're doing. Are you using one PC to record the screen display of a second PC? Are you capturing still images or video? What is the required quality of the captured image/video?
  11. Oct 12, 2011 #10
    I'm using a PC to record a video of a display, a 640x480 VGA output into a PC to TV converter, composite out to a USB capture device, and onto my computer. There is no required quality, I just want the best possible quality.
  12. Nov 4, 2011 #11


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    Science Advisor

    Most modern video cards have very good TV In/Out capabilities.

    Alternatively if that is not an option a TV tuner card will work, but if you can get a decent video card with this built in, it will probably be a lot better (in terms of resolution, and also in performance).

    Can't do this if you have a laptop though. (You have to get something like a USB piece of hardware).
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