Calibrating luminance levels/color for capture from VHS

[Cherbette]

I am operating in Windows XP and using the latest version of VirtualDub to capture via my Diamond One Touch VC500 from VHS tapes...I am capturing in uncompressed AVI (UYVY it says for Capture Pin Color Space). I am trying to figure out how to get the best dynamic range out of my capture with the lights and darks and then hopefully calibrate the colors. I capture uncompressed so I will have the highest possibly quality to work with for restoration and then converting to MPEG2. I am still a bit of a newbie but any help would be much appreciated as to how to properly achieve the best range in color/contrast from while capturing...the default levels for brightness, contrast, saturation, hue etc via the DC500 are TERRIBLE!!!!!!!!!

[Cherbette]

Here are some screencaps...please let me know if any further info is needed:

[Cherbette]

Here's another PrtScr of the Histogram while actually playing a VHS...the previous Histogram capture was just of the VCR's blue screen:

[sanlyn]

UYVY? That means a colorspace conversion, likely more than one, before you get to MPEG. Most color correction is done in RGB (VirtualDub, Premiere, Vegas, AfterEffects, etc.). Most filters use a different colorspace, e.g., RGB (Vdub, Premiere, etc), or YV12/YUY2 (AviSynth). Huffyuv lossless compression lets you capture with no quality loss to YUY2, with smaller files.

Histograms are certainly helpful (you wouldn't want to do any color work without one). If you want to spend some money, or if you're willing to bite the big bullet as I had to do, the best way to check luma (rather than color) is with a proc amp that has a luma meter (http://www.signvideo.com/single_dual_proc-amp_video-processor.htm).

Using the histogram at capture isn't a bad idea. It'll get you into the neighborhood of suitable levels. The problem with VHS is that color is neither stable, uniform, nor consistent. VHS noise affects what you're seeing on the histogram (playback and chroma noise have color, too).

A calibrated monitor is essential if you're picky. It's usually done this way: http://www.tftcentral.co.uk/reviewseye_one_display2.htm

Color probes and free software like HCFR (many 'net posts on this product) can be used to set up your media players, most of which look like crap. At least PowerDVD and VLC have rudimentary color adjustments, but far from ideal. I find that VirtualDub's capture and edit screens are probably hooking into your PC's monitor profile (.icc or .icm color profile). At least, my color probe tells me VDub looks more accurate than PC media players.

If you want to look over your video or process in VirtualDub, here's a handy and popular tool from Trevlac (free, too!):
http://www.trevlac.us/colorCorrection/colorTools.html

Trevlac's website has some gems worth checking:
http://www.trevlac.us/colorCorrection/channels.html
http://www.trevlac.us/colorCorrection/histo.html

[Cherbette]

I am now capturing with huffyuv as my compression but under capture pin where it says color space/compression it still says "UYVY" and there's no other optioin there to select. Is this accurate?

[jagabo]

UYVY is the same 4:2:2 chroma subsamping as YUY2 except the ordering of the Y, U and V components is different. I would adjust the capture card's video proc amp so that the blackest blacks are near the bottom of the histogram, and the brightest brights near the top -- but out of the red zones.

[Cherbette]

@jagabo so you would suggest adjusting the DC500's Video Proc Amp rather than what is done here: http://www.trevlac.us/colorCorrection/histo.html ?

[sanlyn]

@jagabo so you would suggest adjusting the DC500's Video Proc Amp rather than what is done here: http://www.trevlac.us/colorCorrection/histo.html ?

trevlac's filters are for post-processing, not for capture. Use your DC500's proc amp for capture.

With any VHS transfer there's always some tweaking required. That's what post-processing filters are for, not for capture.

[Cherbette]

Thanks so much May I ask for a more detailed description of how to: adjust the capture card's video proc amp so that the blackest blacks are near the bottom of the histogram, and the brightest brights near the top -- but out of the red zones...

Would I do this in a similar way as the above mentioned link by viewing the Color Tools histograms to adjust my Proc Amp?

[sanlyn]

Thanks so much May I ask for a more detailed description of how to: adjust the capture card's video proc amp so that the blackest blacks are near the bottom of the histogram, and the brightest brights near the top -- but out of the red zones...

Would I do this in a similar way as the above mentioned link by viewing the Color Tools histograms to adjust my Proc Amp?

You make that adjustment in the capture histogram by eyeball. The far left end is zero-black, the far right end would be RGB 255 white. VirtualDub uses an RGB 0-255 (sRGB) colorspace. You'd want your darks to avoid banging against the left-hand edge, and keep your brights away from the right wall. If you can, imagine that your histogram is divided into 15 or 20 columns. You'd want to keep colors out of the left-most and right-most columns.

trevlac's tools are for post-processing, not capture. The filters work in VDub's editing windows, but not in capture windows. The capture window's histogram is a calibrator in itself. It shows the averaged values for all the colors; the capture histogram doesn't tell you if your color balance is off (too green, too red, etc.) because it doesn't indicate individual color or saturation values. However, it's a good guide for avoiding captures with crushed blacks or wiped-out brights. What you're really looking at with the capture histogram is a levels control, not a color-balance control.

Keep in mind that scenes in a video don't have to use the entire histogram scale. A very bright scene might take up more room at the right end, while a dark night scene will shift to the left. The main idea is to adjust brightness and contrast levels so that colors don't crash against either side. On most proc amp setups, the "brightness" actually has more control over the black (left-hand) levels, while "contrast" has more effect on the brights. To a certain extent, those two controls interact at least slightly, so that lowering brightness might slightly lower contrast, and so forth. It takes a little jiggling back and forth between the two, but it's not difficult to get accustomed to.

Unless you have a really whacko tape in bad shape, playback is usually within a standard bright/contrast range, once you have it set up in that histogram. However, all VHS is rather unstable; you might hit a scene where the output has horrible, grimy blacks, then a minute later the output gets too bright. VHS is infamous for that sort of thing. This is why it's a good idea to keep colors away from the far left or far right in that histogram. You can always fine-tune with trevlac or other filters later. Those adjustments and ultimate color correction are impossible at the capture stage, with the kind of gear we hobbyists use. That kind of tweaking is what VirtualDub, AviSynth, Premiere, etc., were made for. You'll also find that the denoising filters in VDub, AviSynth, etc., are far superior to any such features in a non-pro proc amp.

[Cherbette]

One other question is how do I avoid "clamping" when capturing from my DC500 via VirtualDub with Huffyuv as my "compression"? According to Trevlac's site, I want to avoid "clamping" for the tweaking I'm trying to do here...

[sanlyn]

There are so many ways that low-end or high-end clamping occurs...it can happen with colorspace conversion, and with many other processes. huffyuv doesn't "clamp" anything, it just compresses whatever it's fed, assuming you haven't instructed your proc amp to do the impossible.

If you set your proc amp controls so that you're visibly losing dark or bright details entirely, you're clamping -- that's using a sharp cut off rather than a gradual leveling-off. Another form of clamping is "burned-up" brights: bright color or luma values are smashed against the right-hand wall of the histogram and starting to climb up it: that's a sharp cutoff that destroys bright-end detail. There's no way to get it back. If you use a filter that won't accept any color above RGB 200, you've set an arbitrary clamping limit at that range.

You seem to be looking for a one-step solution to perfect capture and color correction. It doesn't exist. What you want to do when capturing is to inflict as little damage or data loss as possible, given the gear we work with. You can do some color correction with a proc amp at this stage, but remember that proc amps work with YUV; this allows you to make basic tint corrections when needed for bad tape, but it's a long way from the detailed color grading you'd do in RGB. That level of tweaking comes later -- especially with VHS or other analog sources, where there are just too many variations to completely resolve during capture. The more processing you add to that step, the more you slow it down and risk dropped frames and whatnot. You can make only so much improvement when capturing; details come later. And there's almost always something that needs to be fixed.

[jagabo]

You make that adjustment in the capture histogram by eyeball. The far left end is zero-black, the far right end would be RGB 255 white. VirtualDub uses an RGB 0-255 (sRGB) colorspace. You'd want your darks to avoid banging against the left-hand edge, and keep your brights away from the right wall.

I don't any way of testing this right now, but I think when VirtualDub captures YUV sources the histogram is of the luma channel. So it highlights the under and over shoots:



You want the histogram to come near the two red (or whatever color they are) areas (overall, not every frame) but not to extend into them.

[Cherbette]

You said: overall, not every frame....so the smart thing to do would be to view the entire clip I want to capture? Watching the preview+histogram and adjust as u said? I think I have done this and have done a test capture...how can I display my results for the clip as a whole here?

[Cherbette]

Here is an xvid compressed avi of the luma histogram of my (huffyuv) avi capture with adjustment done to the brightness/contrast to (I hope) avoid clipping. I hope this is okay to post here for your professional analysis

http://www.mediafire.com/?c8acrr3tycp0ms5

[jagabo]

Upload a sample of the captured video itself. The histogram view is too dependent on what settings you used.

[Cherbette]

a 30 second direct stream without audio is going to be about 185mb is that ok?

[jagabo]

a 30 second direct stream without audio is going to be about 185mb is that ok?

Yes. It doesn't even need to be that long. Just pick a representative section or two and upload a few seconds of each.

[Cherbette]

http://www.mediafire.com/?d8d0stac9k64z4h

Here is the clip...let me know if you need it to be shorter...it's 185mb

[sanlyn]

Here is an xvid compressed avi of the luma histogram of my (huffyuv) avi capture with adjustment done to the brightness/contrast to (I hope) avoid clipping. I hope this is okay to post here for your professional analysis

http://www.mediafire.com/?c8acrr3tycp0ms5

The histogram says you're within suitable chroma and luma range (mostly, anyway). There are some slight overlaps, but they can always be tweaked later. Remember, people don't watch histogramn, they watch images -- but you're correct in planning ahead at the capture stage to help prevent blowing out portions of your image. Again, too, this type histogram is a composite of all the color and luma channels. It doesn't say anything about overall color balance.

The histogram doesn't show any obvious clipping. But you still have to examine the video itself, both during and after capture, to determine of colors and specific areas like skin tones look "correct".

A few seconds or 10 secs or so of video should be sufficient, most of the time.

[sanlyn]

http://www.mediafire.com/?d8d0stac9k64z4h

Here is the clip...let me know if you need it to be shorter...it's 185mb

I'll second jagabo's suggestion: it's better to pick out a representative sample of what you want to do or what you might have problems with, and load smaller clips of a few seconds or so.

[jagabo]

I prefer to use the Waveform view instead of the histogram view.



The waveform view is essentially a graph of the brigtness across each scanline of the image. If your image was only one pixel high you would have one clean line in the graph. But since it's many pixels high you have many lines drawn across the graph.

The darkest parts should be near the dotted line near the bottom of the graph. The brightest parts should be near the top dotted line. In this video I would set the black level a little lower -- to get the heavy white line at the lower right to touch the dotted line. Don't worry about a few little overshoots. In this graph they are over sharpening artifacts from the VHS tape.

ColorTools works with the video after VirtualDub has converted it to RGB with a rec.601 matrix. VirtualDub won't show anything below the bottom dottled line or above the top dotted line. I prefer to use AviSynth's VideoScope() instead. It can work with the video while it's still in YUV form:



After a slight levels adjustment:



By the way, I highly recommend you avoid odd frame sizes. Your video is 700x473. A lot of codecs will choke on that 473 frame height. Some will even choke on the 700 pixel width. Stick with mod 16 or mod 8 whenever possible. At least mod 4.

[Cherbette]

@sanlyn I will upload a shorter 10 second clip here in just a few. @jagabo I almost always just capture at SD 720X480 however for this test I thought it would be best to crop out the borders? I must say that the information you added and the results you got were fantastic...I cannot wait to test them out. Also, I'm not familiar with Avisynth at all...but I'm trying to do some reading up on how it works...

[jagabo]

I'm not familiar with Avisynth at all...but I'm trying to do some reading up on how it works...

You can do many of the same things in VirtualDub.

[sanlyn]

@sanlyn I will upload a shorter 10 second clip here in just a few. @jagabo I almost always just capture at SD 720X480 however for this test I thought it would be best to crop out the borders? I must say that the information you added and the results you got were fantastic...I cannot wait to test them out. Also, I'm not familiar with Avisynth at all...but I'm trying to do some reading up on how it works...

I'm into some heavy restoration work tonite (that's why I didn't have time to down 180-plus MB's). So there might be a delay in replying.

I hear a lot of people record to 740x480, regardless of the display size of the source and the final video (for VHS that's usually 4:3, or 640x480). 740x480 rendered DVD video can contain video that will display in any of several display aspect ratios: 4:3, 16:9, etc., etc. Most video hobbyists and a few pros I know will always work with a video in its displayed aspect ratio. It doesn't make much difference as far as color is concerned. After all, red looks red whether your image is distended or square or squished. But distorting the image makes it very difficult to spot and analyze noise and artifact problems -- a consistent horror with VHS, no matter how it's captured.

But that's a matter of personal preference more than anything. BTW, the dark areas of the capture posted above by Jagabo shows a lot of annoying tape noise in the darks. When the AVI is rendered to DVD, that noise will be accentuated and will turn somewhat mushy and look brighter, taking up databits that could better be used for cleaner areas. Try running a little of the video thru VirtualDub's temporal smoother filter set to about 3. AviSynth has a similar temporal cleaner built in, and there are countless others.

I'm still learning AviSynth, and you can work wonders with it. Don't expect to pick it up in a weekend. It's easier to start with VirtualDub. I don't think there are any one-tool solutions. Eventually you'll find yourself using both programs. But any detailed color correction will find you learning a lot about working in RGB.

[jagabo]

Another tool you'll find very useful with VirtualDub is CSamp. It shows you the RGB values under the mouse cursor as you move around the screen. VirtualDub should have that feature built in for it's two view panes!

[sanlyn]

@sanlyn I will upload a shorter 10 second clip here in just a few. @jagabo I almost always just capture at SD 720X480 however for this test I thought it would be best to crop out the borders? I must say that the information you added and the results you got were fantastic...I cannot wait to test them out. Also, I'm not familiar with Avisynth at all...but I'm trying to do some reading up on how it works...

I'm into some heavy restoration work tonite (that's why I didn't have time to download 180-plus MB's). So there might be a delay in replying.

I hear a lot of people record to 740x480, regardless of the display size of the source and the final video (for VHS that's usually 4:3, or 640x480). 740x480 rendered DVD video can contain video that will display in any of several display aspect ratios: 4:3, 16:9, 2.35:1, 1.66:1, etc. Most video hobbyists and a few pros I know will always work with a video in its displayed aspect ratio. It doesn't make much difference as far as color is concerned. After all, red looks red whether your image is distended or square or squished. But distorting the image makes it difficult to spot and analyze noise and artifact problems -- a consistent horror with VHS, no matter how it's captured.

But that's a matter of personal preference more than anything. BTW, the dark areas of the capture posted above by Jagabo shows a lot of annoying tape noise in the darks. When the AVI is rendered to DVD, that noise will be accentuated and will turn somewhat mushy and look brighter, taking up databits that could better be used for cleaner areas. Try running a little of the video thru VirtualDub's temporal smoother filter set to about 3. AviSynth has a similar temporal cleaner built in, and there are countless others. It looks pretty OK for VHS, but some streaking and jaggies (worn video head streaking? tape damage? field polarity error?) chroma noise, cross-hatches, and block noise in areas of fine color gradation. The usual VHS suspects. Almost all of this can be fixed in VirtualDub and/or AviSynth.

I'm still learning AviSynth, and you can work wonders with it. Don't expect to pick it up in a weekend. It's easier to start with VirtualDub. I don't think there are any one-tool solutions. Eventually you'll find yourself using both programs. But any detailed color correction will find you learning a lot about working in RGB.

[Cherbette]

Do I want my waveform to look something like this?


Here are the adjustments I made in filters:


And here is how I'm capturing....it says Directshow next to the VC500 so I just wanted to make sure I am not supposed to be choosing one of the other options:

[jagabo]

As long as that capture device is working you should be ok.

That waveform graph looks about right. If you can, you want to adjust the capture device's proc amp setting rather than filtering in post processing. Most capture devices capture at 10 or 12 bits and the proc amp adjusts the video before being reduced to 8 bits and given to the capture program. That gives better results than adjusting the levels after capturing where everything is handled in 8 bits. It's not a huge deal with VHS because all the noise hides most of the problems. As long as your levels aren't too far off.

[Cherbette]

What would the code be that I need to put into notepad to convert to RGB with Avisynth and open with Virtual Dub...then I just make my adjustments and Save AVI As...? Working with scripts is very foreign to me but I'm trying to get it

So far I have:
AviSource("C:\Documents and Settings\Administrator\Desktop\Love and Pain.avi")
ConvertToRGB(matrix="PC.601")



I think I'm on the right track? Here is the window that pops up once I've opened the above code as an ".avs" file with virtualdub, done my adjustments, and Save AVI As uncompressed RGB



I also posted a thread here: https://forum.videohelp.com/threads/339042-Rendering-Effects-in-Premiere-CS3

I am new to Premiere CS3 as well. I have used other software but nothing that advanced. I was hoping some of you familiar with Premiere might be able to help in that area as well.