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Unofficial VirtualDub Support Forums > Newbie Questions > Problems With Color In Vdub (black Levels)

Posted by: Seraphic Oct 12 2009, 09:57 PM

Hi, Could some people who have photoshop (phaeron), take a look at the attached file and see what could cause such issues with color? I have Canopus HQ file here that I also converted to uncompressed uyvy (also yuy2 and rgb just for testing). But when I open the the raw Canopus HQ video and test rgb converted video into Vdub the color is washed out. Opening the test uyvy and yuy2 looks almost correct, but there are color brightness issues. Only when the raw Canopus HQ is played in WMP the color is normal, but not when opened in Vdub. Below is a photoshop file with several images that show the color issues I have encountered. Just cycle the images and you see how they change, only the top one played over WMP is correct. Also notice how the bottom two images (raw video and converted rgb) have like a whitish overlay to them and the others do not? http://www.mediafire.com/download.php?qmjmyqnbzzz So it appears there is some kind of decoding error or color space conversion issue. Any thoughts?

Posted by: phaeron Oct 12 2009, 10:46 PM

Star Ocean 4... boy, that was a letdown.... This is most likely a YCbCr levels mismatch. The problem is usually a combination of the video driver interpreting YUV as 0-255 instead of 16-235, and sometimes the codecs do too, resulting in a cluster#&$* of mismatched levels that sometimes cancel out. One way you can tell if this is happening is to temporarily turn off video acceleration in Display Settings > Advanced or in the video player. If the player changes contrast then you've got the video problem AND you've got something else in your pipeline that is also contributing an opposing mistake. VirtualDub always uses the proscribed 16-235 for luma and 16-240 for chroma when reading and writing YCbCr formats. BTW, Canopus, or Cineform?

Posted by: Seraphic Oct 12 2009, 11:04 PM

In this case I was using Canopus. But I also have access to Cineform, which in this case, when opened in VDub, has the same whitish overlay like the raw Canopus and converted rgb versions. I'll try your video acceleration suggestion and post results. Also, the only two color space conversion options there appear to be for Canopus are: RGB has ITU-R BT.601 range or Convert RGB range [0,255] as IRE [0,100]

Posted by: Seraphic Oct 12 2009, 11:35 PM

You know, I forgot, ATI removed the ability to disable hardware acceleration. The raw Canopus video has correct color in WMP, it was just the problems when opening in VDub (as seen in images).

Posted by: Jam One Oct 13 2009, 11:13 AM

QUOTE I have Canopus HQ file here that I also converted to - Where (I mean, what soft) did you do this conversion, could you tell it in more detail ? YUY2 & UYVY look identical to WMP's playback (in Corel PhotoPaint, calibrated monitor, all due color management/icc profiles engaged). (The issue is undoubtedly related to levels.) (Did I say it before that screwing levels is GrassValley's hobby?=) ) ---------- If you did your conversion with Canopus codec -- please try "Convert RGB range [0,255] as IRE [0,100]" next time. ---------- Some problem may reside in handling the GV's software the right way, when dealing with RGB. Let's say, we use the setting "RGB has ITU-R BT.601 range" in Canopus codec. Consequence-1, encoding case: The program does assume that your video is supposed to have levels of 16-235 within RGB-encoded file. This leads us to the effect of "washedness-out" later on -- since other software does believe RGB-encoded file must have levels of 0-255, and other software plays your video back AS IF it was 'RGB 0-255'. (You see the picture on your screen.)* Consequence-2, decoding case: The program does assume your video has ALREADY got levels of 16-235 within RGB-encoded file. If it is really so -- everything should be OK. But if it is not... You will get too high contrast (clipped shadows & highlights). ---------- (The bad thing about GrassValley's products is that you may encounter some situations when abovementioned things happen unnoticed. You just CAN'T get to the mentioned codec's settings in Canopus ProCoder. So... When, say, your sole desire is to convert your uncompressed RGB to DVD format -- you have to either make sure the RGB has got 16-235 levels prior to feeding it to ProCoder, or to apply colorspace correction video filter... which tends to decrease the overall video quality for a [stupid] reason it runs on the video AFTER the [improper] decoding.) ______ * -- the good thing about this -- you can deliver such uncompressed RGB material for TV-broadcasting.

Posted by: Seraphic Oct 14 2009, 08:49 PM

I used EDIUS to do the conversions. But I think it has to do with two settings White vs Super White. QUOTE In "White" RGB black (0,0,0) translates to ITU-R BT.601 "safe" black and RGB white (255,255,255) translates to ITU-R BT.601 "safe" white. In "Super White" RGB black translates to super-black, and white translates to super-white. If your RGB images have already been compensated for broadcast with ranges 16,16,16-235,235,235 then you should use it in Super White mode, otherwise your blacks will turn muddy and whites will turn gray. If your RGB images are normal, then use White to ensure that black and white ends up in the safe range. If you use Super White, your blacks will become super-black and whites will be super-white and things will be out of safe range. I'm not sure why it worked, but opening up the canopus hq codec encoder config in VDub and switching to RGB convert fixed the issue with opening Canopus HQ files in Vdub. But exported conopus hq files from EDIUS as uyvy/yuy2/rgb still open up with wrong color in VDub. It is interesting you were able to get YUY2 & UYVY to match the WMP version. But sounds like you had to enable several filters.

Posted by: Seraphic Oct 23 2009, 11:05 PM

~

Posted by: iStrain Apr 8 2010, 10:45 PM

I'm having the same problem with lighter-than-black blacks. I've tried dozens of plugins and codecs for different colorspaces, RGB and YUY,YUV,UYVY,YV12 renders, posterize, threshold, color tweaks, you name it, and nothing forces Vdub to render blacks as RGB(0,0,0). It insists on rendering StudioRGB black(16,16,16). I'm not making a DVD; I only want this video rendered for computer monitor viewing. The original file is a .vob which I converted to xvid (mp4) for editing. I also tried editing the .vob directly, importing into Vdub with fccHandler's mpeg-2 plugin. I viewed the .vob and the xvid conversion in various players (VLC, MP Classic, etc.) and they looked fine, so this is definitely Vdub's doing. Black is true in Vdub's preview window(s), just not in the rendered file. I have Animation Shop 3, so I suppose I could use the ChangeColor function, but it crashes (undo buffer overrun) with larger files and I'd rather not have to select say a hundred frames at a time and do it manually the hard way. Is there anything I can do in Vdub to obtain true (ComputerRGB) black and white? Is there a Studio-to-Computer RGB color mapping plugin that would work?

Posted by: Jam One Apr 8 2010, 11:18 PM

...You seem to contradict yourself... You say "Black is true in Vdub's preview window(s)..." So. That is really supposed to mean you've got the right conversion. VirtalDub does already render the video the right way. But later you're asking about quite different - you're asking about this same conversion. You need to check out what's going on in your ENCODER, not something to "fix" an alleged "Vdub's doing". I tend to believe there's no need to fix what's not broken =)) What is your target format and encoder?

Posted by: iStrain Apr 9 2010, 03:02 AM

The darkest black in the preview window is darker than the darkest black in the saved output file. Hence, Vdub is "doing this", meaning it's showing me darker blacks in preview than it's giving me in the output file. I didn't mean to imply that I can't be at fault for this particular issue. Maybe I am. Maybe I'm not. If others are getting RGB(0,0,0) in their output files, then I am at fault. Despite quite a lot of Googling (and forum searches), I've yet to read where others are in fact accomplishing this. There's a lot of talk about it, but oddly, no solutions (via Vdub) are mentioned in all those threads. I fail to see a logical reason for the discrepancy between preview and final output to file, though, especially if Vdub is using the same rendering scheme for the preview as it is for the final output to file -- which seems to be what you're suggesting. Shouldn't they look the same in that case? Shouldn't the preview alert the user to potential problems in the final/saved version, so they can be rectified while in edit mode? Why show me dark blacks (and have me make adjustments such as contrast to desired levels) in preview if the final output is going to be dramatically different? My target format is... anything that will yield RGB(0,0,0) black. The desired encoder is.. same as above. I'm not too fussy, I just want black black instead of gray black.

Posted by: phaeron Apr 9 2010, 03:22 AM

You have a problem with the codec that is being used for encoding. The output preview pane shows what is sent to the encoder.

Posted by: iStrain Apr 9 2010, 11:32 PM

Great! Now that we've established it's a codec/usage issue, has anyone suggestions as to the proper codec to use and how to configure it so that I might obtain rgb(0,0,0) blacks in my videos? I've tried most of them, to no avail. What am I doing wrong? Again, I don't care what format the video ends up in. I'll deal with that later. All I want right now is for Vdub to somehow give me rgb(0,0,0) black in encoded/saved files.

Posted by: Oxyandy Apr 10 2010, 05:04 AM

If you open your output file with virtualdub and compare to original.. How are black levels then ?? What player are you using to view final output ?

Posted by: iStrain Apr 10 2010, 08:31 PM

Oxyandy nailed it. The problem is with the player(s). I viewed the original.vob, the converted original (to various types) and Vdub edit (output to file) using Vdub, Media Player Classic, Media Player 11, VLC, Winamp, Nero Media Player, Nero ShowTime, Real Player and YouTube (Firefox). Only Vdub, VLC, Nero(both) and Firefox present the same dark black (rgb0?) in the Vdub output file, with the others displaying a lighter black (rgb16?). I got VLC to behave by unchecking the "Use hardware YUV->RGB conversions" box. No settings in the Media Player(s), Winamp or Real Player remedy the situation. Media Player 11 produced varying horizontal color bars, monochrome portions, chroma/luma noise and various artifacts -- ironically, disabling "high quality" mode in video acceleration fixed this. QuickTime couldn't open the test file, nor could it find a suitable codec, apparently (all blank frames on playback).

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