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Originally Posted by homefire
I have DVD's that were converted from VHS with a low grade toshiba dvd recorder and the video format of the DVD is interlaced YUV 4:2:0.
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4:2:0 interlaced is standard spec for DVD, and also for standard-def BluRay, and for 1920x1080 BluRay at 29.97 or 25 fps, and for most TV broadcast material, not to mention a lot of streaming stuff. I'll bet at least some of it isn't interlaced but is telecined or uses some form of pulldown, or could be progressive but mastered as interlaced. Deinterlacing in itself is not an improvement, since deinterlacing is a destructive process. Don't deinterlace unless you have a reason for doing so.
Quote:
Originally Posted by homefire
From what I've read and understand filters and plugins have less information to work with YUV 4:2:0 than YUV 4:2:2.
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That's true. Results also depend on how well a specific process handles the working colorpsace.
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Originally Posted by homefire
Will filters work better if I were to upsample from YUV 4:2:0 uncompressed to huffyuv 4:2:2?
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Any time a video is decoded for processing, it is decompressed regardless of colorspace. Compression refers to encoding, not to color resolution. Why are you specifying
huffyuv? Lagarith and UT Video codecs work with more colorspaces than huffyuv does, although there's nothing wrong with it.
Sometimes a higher chroma resolution is a better choice (cleaner, more detail retention, less destructive, fewer interpolation errors, etc.), sometimes it isn't. If a filter isn't designed to work in a particular colorspace, it can't be used in other colorspaces anyway. Many filters can work in more than one colorspace, most can't. Some multispace filters work better in one colorspace than in another. How do you find out? You use it, you find discussions about it (usually in doom9.org), you perform very specific and highly controlled experiments -- the latter means you have to know a lot about programming and filter design.
To a general extent, a filter that can work in a higher color resolution gives superior results. How superior? Again, it depends. Usually the differences are subtle, but not always. One recommendation used by colorists and mastering experts is that resizing is cleaner when the color resolution is higher -- of course, much also depends on the resizer. As you can guess, there are different resizers. Try some of these in Avisynth:
http://avisynth.nl/index.php/Resize. There are also special resizing filters or procedures. One favorite for downsizing is iResize, which basically uses the Spline36Resize algorithm (
http://blog.davidesp.com/archives/269). The coded text in that link that begins with "function IResize" is saved as an .avs text file for use as an Avisynth plugin. It was designed primarily for use with interlaced material, but it can be used as-is with either interlaced or progressive.
How do you know which colorspaces a filter can use? Look at the documentation. For a quick reference you can look at the following plugin listing that includes a column of allowed colorspaces:
http://avisynth.nl/index.php/External_filters. For Avisynth built-in functions such as ColorYUV, consult the documentation or browse this page that lists filters and their intended color formats:
http://avisynth.nl/index.php/Internal_filters.
Which filters work better in which color spaces (the most common ones for VHS restoration)?[/QUOTE]
There is no answer. Most of the classic Avisynth filters for VHS restoration use Yv12 only, some are YUY2 only, many can use YUY2 and YV12. The filters used depend on the problems they address. The deinterlacer QTGMC has the original basic version that works only in Yv12, but there are newer versions that can use multiple colorspaces. The advantage of the original, which is still a favorite, is that it's time-proven and always works. The problem with the newer versions is that they change every few months, they often work only in the computers of those who designed them, revisions almost always have bugs that are "fixed" in new revisions a week later, etc., etc. Newer versions of QTGMC can also work with 16-bit dithering if you're willing to master the specialized and complex procedures and support plugins required.
I'd suggest that you start with what most refer to as the old classics and gradually move up to the newer stuff, keeping in mind that newer isn't always better and is often a pain in the neck. Most tried and true classics are 32-bit, but there are 64-bit versions if you don't mind waiting around for new updates from 32-bit (which in many cases will never happen). The newer 64-bit guys use more colorspaces. If they can fill the bill for you, go for it. I find the current choices too limited and poorly documented.
Another consideration is that if you're using a batch of filters some of which require different colorspaces, it's best to stay within one colorspace before moving to the next, rather than jockey back and forth between colorspaces. Colorspace conversions involve math rounding and interpolation errors. Change colorspaces often enough and those errors add up, degrading quality.
Quote:
Originally Posted by homefire
I've read that avisynth is better than virtualdub at converting color spaces due to their modified algorithm.
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For the most part, that's true. And
VirtualDub is better at most conversions than Adobe Premiere Pro and other NLE's most of the time.
Quote:
Originally Posted by homefire
Is there a better alternative?
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Not that I know of.
There is still a [supposed] problem with the way VirtualDub converts interlaced YV12 to RGB, but the rumor/report/assumption is that it's [supposed to be] fixed in v1.9 and later. Most people don't worry about it. But if you're really concerned you can always use an Avisynth script to open your Yv12 video and convert it to RGB formerly and properly before applying VirtualDub filters (
http://avisynth.nl/index.php/Convert). If you're not applying RGB filters, no need to convert.
Some people say that Davinci Resolve does good color conversion. Others disagree. Those who discuss it give no information one way or the other about how DaVinci does it (or doesn't do it) and no one seems to know how to post comparative results. The word "Pro" in software names has nothing to do what actually happens. For VHS work the gargantuan software bloat is often overkill and a silver bullet fantasy by those who don't know very much about color work and who think the pricey software will automatically solve all their processing problems for them. If you're going to get involved with complex software of that nature it's strongly advised that you get advanced knowledge of what you're doing and how the product works. Most people use Adobe and DaVinci the same way they would use a cheap $50 editor. On those terms you can accomplish more with Avisynth and VirtualDub, and they're free. It depends on how much you're willing to learn to to get the best from any product or method.
Opinions otherwise are welcome and necessary.