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  1. Banned
    Join Date
    Oct 2004
    Location
    New York, US
    Search Comp PM
    Question about VirtualDub's capture filters. I don't refer to plugin filters, but to this proc amp control:

    Image
    [Attachment 10676 - Click to enlarge]


    According to what I get from VDub's documentation, it's obvious that using a regular plugin add-on would convert input to RGB and then back to whatever is intended as the capture colorspace. In this case I'm capturing NTSC VHS with an ATI AIW 9600XT and saving as huffyuv YUY2. My understanding is that the "proc amp" control does not convert to RGB, which would force a conversion to YUY2 after the proc amp is processed.

    The only controls I'm using are brightness and contrast to make a basic levels correction and save darks and highlights from destruction. Using the other controls is useless with VHS, which changes color balance with every scenes change. I determine the settings by using the capture histogram and cropping all black borders (I restore the borders when I start the capture).

    Unless there's another way to do it . . .? I can't use my SignVideo or BVP-4 proc amp with this particular video because Macrovision causes problems with both of them (discussed elsewhere). I got very good results using the basic proc amp controls on my AVT-8710, but I can't use that either because the AVT throws dot crawl thru its s-video output (typical captures here: https://forum.videohelp.com/threads/331681-s-video-artifacts?p=2134863&viewfull=1#post2134863). So the capture filters I came up with were those in VirtualDub capture. I'm using a Toshiba DVD recorder for its line-tbc pass-thru. works great - but its image controls are too fiddly; they are notch controls instead of continuous sliders, so they give either far too little or far too much correction.

    This is just an overall correction for capture. As with typical VHS, there's still work to do later with ColorYUV and RGB filters.
    Last edited by sanlyn; 21st Mar 2014 at 07:39.
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  2. That's not really VirtualDub's proc amp -- it's the capture devices proc amp. VirtualDub just give you access to it. You can access that control interactively using GraphStudio or GraphEdit. Add the capture filter and select its properties. Go to the Proc Amp tab. You will be able to see the picture changing in VirtualDub as you adjust the settings. VirtualDub's histogram display while adjusting the proc amp in GraphStudio:

    Click image for larger version

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    Last edited by jagabo; 26th Jan 2012 at 11:59.
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  3. Banned
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    Oct 2004
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    New York, US
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    Excellent, jagabo! Without the tools you mention, I do see the histogram OK in VDub but not the image changes. So it's some back-and-forth and stop-and-check fiddling without those tools.

    Oh, my. So much to learn, so little time. You guys will have me producing some decent video, if you don't wear me out first .
    Last edited by sanlyn; 21st Mar 2014 at 07:39.
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  4. Banned
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    Out of curiosity I gave VirtualDub's "white boost" and "black boost" auto control in capture a try. Kinda like an auto levels feature, and it actually worked well. Black borders in a video make the results look a little thin at the dark end (can be corrected later) but it did a decent job of holding bright luma levels down and helped retain bright detail from the typical VCR's overly contrasty output. There doesn't seem to be any 16-235 "clamping", but more of a gradual alteration at dark and bright extremes. I'll have to give this a try later with black borders cropped. With borders present, the lower midtones look somewhat compressed and lacking in "snap" or crispness.
    Last edited by sanlyn; 21st Mar 2014 at 07:40.
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