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  1. Hello there.

    I'm having a problem with a TV which has a little bit of color fringing due horizontally displaced chroma when using the composite input. I was going to deal with that by counter-effecting that in the video files, but it just came to my head that, perhaps it's possible to somehow fix that problem by 'modding' the component cable with some electronics, for example, 'shifting' the U and V channels a little bit to the right OR the Y a little bit to the left (although I'd rather use the color channels because if the apparatus create some kind of noise it's going to be less noticeable). I know nothing about how the signals are transformed into image, but perhaps some kinda delayed repeater could do the trick.

    Is it possible to do that?

    Thank you in advance.
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  2. You want to delay the U and V channels to shift the to the right. I think you can do it with a simple OP amp circuit: http://electronicdesign.com/analog/accurate-analog-delay-circuit

    Or just use longer cables for the U and V channels. I think you get on the order of 5 nanoseconds delay per meter. As a reference, a single pixel of a DVD is about 75 nanoseconds. So you'll need 25 meters of cable to shift the chroma right by a pixel. Not practical I guess.

    There were some analog delay chips but they were designed for audio applications -- the delay would be orders of magnitude too long. http://en.wikipedia.org/wiki/Bucket-brigade_device
    Last edited by jagabo; 16th Feb 2015 at 00:52.
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  3. What kind of source you use to reproduce issue?

    This problem is usually covered by measurement named Chroma/Luma Gain/Delay http://www.maximintegrated.com/en/app-notes/index.mvp/id/3634
    and it should be specified by your TV/Source vendor.

    Correcting this problem in analog domain is not correct - best is to address it on source in digital domain - usually change in firmware is sufficient (and trivial - most of chips support this kind correction by few bit value in particular register).
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  4. You can also do this in software during playback. For example, you could use ffdshow as your coded and add AviSynth's ChromaShift() function to shift the chroma channels. Here's MPCHC playing a video with ffdshow shifting the chroma 8 pixels to the right:

    Click image for larger version

Name:	chromashift.jpg
Views:	524
Size:	108.3 KB
ID:	30322

    Or you can write your own shader that works with MPCHC:

    Click image for larger version

Name:	shader.png
Views:	555
Size:	34.9 KB
ID:	30323
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  5. Originally Posted by jagabo View Post
    You want to delay the U and V channels to shift the to the right. I think you can do it with a simple OP amp circuit: http://electronicdesign.com/analog/accurate-analog-delay-circuit

    Or just use longer cables for the U and V channels. I think you get on the order of 5 nanoseconds delay per meter. As a reference, a single pixel of a DVD is about 75 nanoseconds. So you'll need 25 meters of cable to shift the chroma right by a pixel. Not practical I guess.

    There were some analog delay chips but they were designed for audio applications -- the delay would be orders of magnitude too long. http://en.wikipedia.org/wiki/Bucket-brigade_device
    Awesome! Thank you very much!

    Originally Posted by pandy View Post
    What kind of source you use to reproduce issue?

    This problem is usually covered by measurement named Chroma/Luma Gain/Delay http://www.maximintegrated.com/en/app-notes/index.mvp/id/3634
    and it should be specified by your TV/Source vendor.

    Correcting this problem in analog domain is not correct - best is to address it on source in digital domain - usually change in firmware is sufficient (and trivial - most of chips support this kind correction by few bit value in particular register).
    The TV is old and I didn't notice the problem in the past, perhaps I wasn't too picky or perhaps it wasn't there. The fact is, the problem is on the component input of the TV.

    Originally Posted by jagabo View Post
    You can also do this in software during playback. For example, you could use ffdshow as your coded and add AviSynth's ChromaShift() function to shift the chroma channels. Here's MPCHC playing a video with ffdshow shifting the chroma 8 pixels to the right:

    Image
    [Attachment 30322 - Click to enlarge]


    Or you can write your own shader that works with MPCHC:

    Image
    [Attachment 30323 - Click to enlarge]
    Yes, I was planning to solve the issue using the ChromaShift but since the problem is specific to the component input, it's much better imho to solve the problem with a cable so no matter what I plug in there the image will be okay.

    Thank you very much guys.
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  6. Originally Posted by Szabo2 View Post

    Yes, I was planning to solve the issue using the ChromaShift but since the problem is specific to the component input, it's much better imho to solve the problem with a cable so no matter what I plug in there the image will be okay.

    Thank you very much guys.
    Well... in theory you can use one of analog delay lines - there is few types of them - but this kind of problem should be addressed in correct place - addressing it in external device seem to be inefficient.
    Length of cable problem should be less than mentioned previously (velocity factor is lower than 1) - i assume 20 - 30 cm should give around 1 - 1.25ns.
    Side to this there are specialized devices http://www.intersil.com/en/products/audiovideo/video-ics/cat-5-analog-delay-line---ske.../ISL59921.html they use similar to mentioned BBD/CCD idea .
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