Quantcast Virtualdub and chroma interlacing - digitalFAQ Forum
  #1  
10-20-2011, 09:16 AM
unclescoob unclescoob is offline
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I need my mind put to ease on this issue.

I hear all different types of comments on this, and would like for the pro's here to please clarify this so that I can put this to rest and continue with my restoration:

I've read that Virtualdub(Mpeg-2) does not handle interlaced chroma accurately. I have also read that VirtualdubMod handles it better. Others state that since Virtualdub only deals with RGB, it is advisable to convert my ripped VOB file to RGB(32) first before opening it in Virtualdub, due to this chroma inaccuracy.

But when I have done some restoration with Virtualdub on some clips and played them on my TV, it looks fine. The only thing I notice is that in some scenes, if I press pause, the chroma appears as if it "jumped" out of the image outline. Not sure if this has anything to do with the issue.

So my question is, how true is this? Is it ok to open my ripped VOB with Virtualdub straight, or should I do a small avisynth script and convert to RGB first? Keep in mind that I still need to convert to YV12 for HcEnc.

Thanks alot folks.
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  #2  
10-24-2011, 10:32 PM
dyfan dyfan is offline
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You might consider choosing your words a little more carefully when you create a post because you haven't had an instantaneous reply to your question...Maybe also consider paying the membership fee to join? The site staff here will eventually address you...They just may not be in a position to stop/drop whatever they're doing to accommodate you. Please try to exercise a little patience, okay?
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  #3  
10-25-2011, 12:13 AM
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Regarding reply time, see this: When Will My Question Be Answered?. In the event a post does go unanswered, it can be for any number of reasons. A member can ask for an update, if he/she feels the post has sat for too long -- but do so with some tact and respect, please. As dyfan has stated, it's not always possible to stop systems in use on projects to answer forum posts. Thanks.

Quote:
I've read that Virtualdub(Mpeg-2) does not handle interlaced chroma accurately.
Correct -- sort of. By default, VirtualDub handles interlaced MPEG chroma incorrectly. However, for MPEG-2, you can manually change the color depth to YUY2 4:2:2, under the VirtualDub menu Video > Color Depth... This will work most of the time, especially for MPEG-2 content sourced from DVDs (homemade or commercial).

vdub-YUY2-MPEG2 chroma.jpg

Quote:
I have also read that VirtualdubMod handles it better.
Natively, yes, it properly reads MPEG-2. However, VdubMod is years out of date. VirtualDub is currently at version 1.10.x, while VirtualDubMOD is at least 5 years behind the times, on version 1.5.x. The biggest differences are lack of certain native filters (Yadif based deinterlacing, for example), or outdated and inferior native filters. No, these native filters cannot be added to older versions, at least not by any known methods.

Quote:
Others state that since Virtualdub only deals with RGB, it is advisable to convert my ripped VOB file to RGB(32) first before opening it in Virtualdub, due to this chroma inaccuracy.
Unnecessary and inaccurate (RGB24).

Quote:
But when I have done some restoration with Virtualdub on some clips and played them on my TV, it looks fine.
I've noticed workflows where the color depth was not altered for an MPEG-2 capture, and VDub definitely read the interlacing incorrectly. The video was filtered, and remained interlaced the whole time. The video was output as Huffyuv AVI, and dropped into MainConcept Reference. The output from Reference was perfect -- no issues were observed upon close inspection. This is why I really never noticed the issue until more recent years, when I started to handle deinterlace content for streaming and restore workflows.

Quote:
The only thing I notice is that in some scenes, if I press pause, the chroma appears as if it "jumped" out of the image outline. Not sure if this has anything to do with the issue.
If this is the case, then it may be a filter is causing the damage. Or it could be VirtualDub's poor handling of the source's interlaced chroma. Either way, you need to test, slowly removing variables until you can clearly identify what is responsible. Quite a few NR filters damage chroma, adding ghosting distortions. You need to be only as heavy as needed (aka as gentle as possible) with filters. Remembering, of course, that restoration is about making it better -- not making it perfect. Find the output that has the least desirable flaws removed or reduced, while understanding the output may still have errors present when done.

Hope that helps clear it up for you.



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  #4  
10-25-2011, 09:02 AM
unclescoob unclescoob is offline
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I really do apologize for the nastiness of the previous post. I could have used better demeanor. I completely understand that questions will not be answered right away. This is, after all, a hobby and not a medical dilemma. Having said that, I hope some can also, by the same token, see a little bit of my side here: 3 views or so and no answer after a day or two? I totally get it. But after a week or so of posting a basic question, and seeing twenty somewhat views and not ONE response... Well, I kind of imagine the following scenario: "Hmmm, let's see what this post is about" *click..read....read...read* "Oh!". *click out*. It almost feels disrespectful. Lordsmurf, this does not apply to you. You always answer my questions at one point or another. But most of my questions are for anyone to answer, even if it's "I'm not sure". It's the principle of the courtesy. Just like I should have the common courtesy to utilize better manners, perhaps we ALL should utilize the same principle on manners by at least giving each other the respect of an acknowledgement? Even if it's a thousand views and ONE response...and the response is irrelevant. But it's still courtesy. And it applies to me too.


Ok...back to business. Smurf. NeatVideo is second to first in my workflow. Being that NV converts videos in VD from RGB to YCrCb, would your suggestion to convert to YUY in V-dub still be necessary? Keep in mind that after filtering, I am converting the file to YUV12() with Avisynth to dump into HcEnc. I know too many conversions is not good either, so I'm just trying to find the best workflow here.

One more thing (LordSmurf, if you can possibly assist me with this) and it should clear things up for me: Before I even touch my video with Virtualdub, I am first planning on converting my ripped VOB to an index file first (with DGIndex), then converting that index file to an avs script file (for the purpose of allowing the mpeg-2 stream to be read accurately with Virtualdub). THEN, I was going to open that in Virtualdub, do my filtering, and save as an AVI (to convert back to an AVS file). This is all, as I stated, to allow Virtualdub to correctly read my mpeg-2 stream. Is this workflow better than just opening the ripped VOB file with Virtualdub and jumping right in, or is it deemed unecessary?

I really appreciate it.

Last edited by unclescoob; 10-25-2011 at 09:13 AM.
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  #5  
10-25-2011, 10:44 AM
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kpmedia kpmedia is offline
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Sometimes it's an issue of "Hmm, I wonder what that is? [reads] Oh, I can't answer that yet, I'll get back to it when I can."
Views are logged by all visitors, so drive-by Google traffic is more likely people looking for answers, not looking to help others.

Keep both of those in mind. Nobody gets ignored on this site.

Colorspace transitions between RGB and YUV 4:2:2 really are not drastic enough (for consumer sources) to make a fuss over.
At this late date, DGindex is redundant, open in VirtualDub directly.
In the past 2,000+ MPEG files I've opened this way, only one had oddities. That whole file was fubar anyway.

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  #6  
10-25-2011, 10:54 AM
unclescoob unclescoob is offline
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Quote:
Originally Posted by kpmedia View Post
Colorspace transitions between RGB and YUV 4:2:2 really are not drastic enough (for consumer sources) to make a fuss over.
So it doesn't make much of a difference if I convert or not, is what you're saying? If so, what about the issue with V-dub handling interlaced chroma inaccurately?

Quote:
Originally Posted by kpmedia View Post
At this late date, DGindex is redundant, open in VirtualDub directly.
In the past 2,000+ MPEG files I've opened this way, only one had oddities. That whole file was fubar anyway.
Ok, thanks
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  #7  
10-25-2011, 11:12 AM
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kpmedia kpmedia is offline
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Quote:
If so, what about the issue with V-dub handling interlaced chroma inaccurately?
Make the Color Depth YUY2 change as per post #3 by LS. (Alter the decompression aka input method.)

Problem solved.

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