Is this chroma bleeding?
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The whites in the letter of the album should be white, but there appears to be some other colors mixed in in areas. Is this chroma bleeding, or something else? The overall video has already been color corrected in Premiere, but I think that is the limit of what it could help with.
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That looks more like cross-color artifacts. It looks like the vcr that recorded the tape was not able to separate the colour and brightness data cleanly, and some of the sharp black-white as part of the colour signal. Additionally there seems to be some colour noise all over the picture.
There are filters for avisynth and virtualdub that can help reduce these artifacts, don't know too much when it comes to premiere. Chroma bleeding is what you see a bit of on the edge of the bright red part of the man's shirt. The red colour bleeds onto the background a bit, as VHS doesn't have sufficient color bandwidth for sharps transition between different colours. Granted, in this it seems to be that the colour is offset slightly to the left so there may not be a lot of actual "bleeding". |
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It looks like a bit of high frequency noise to me. There is definitely some problem separating out the chroma component.. perhaps the comb filter is old or the cables are not great.
Here is what it looks like with even a poor quality median filter.. which cuts off the high frequency noise. I agree that is doesn't look like much if any color bleed. The dark evergreen color in his sweater is much easier to distinguish from the background once the high frequency noise is muted just a little. You can even see shadows cast on the green. That's how distracting the uniform high frequency noise actually is. |
Thanks both for the help. The photo does seem to be a bit improved with the filter. The image is actually based on an old U-Matic tape, but they are similar. I just did not know how to identify it to correct it.
Is the language of Avisynth pretty easy to learn for someone who does some programming? Do you think I could fix the problems in the screenshot (plus a few odd oxide dropouts that appear from time to time) myself rather quickly? I am mostly concerned about knowing when to use the right filter at the right time, which comes down to knowing how to identify each issue. Thanks again. |
I believe there are guides already written for using Avisynth on this website, you just need to look for them.
If Sanlyn is around he may respond and give you a proper appraisal of everything that needs correcting. He can do amazing things with Avisynth but generally needs an uncompressed video clip to demonstrate, he will blow your socks off with the magic he can do. There are other people that know the program well but they tend to come and go over time, Sanlyn is the current expert as far as I know here in mid-2019 hodgey is correct there are filters in Avisynth (and) in Virtualdub.. but Avisynth is used for post production (after) the video has been captured with a batch file. Virtualdub is usually used to process video while its being captured with a filter chain.. but it puts a strain on the capture process itself and can cause problems on some hardware, leading to dropped frames and out of sync audio with video. Its usually best to do one thing at a time, capture then post process. A major factor in any "correction" project is you need to capture Uncompressed with a lossless encoder like Huffyuv or Lagarith (if your CPU can handle it) that grabs the most video detail and color resolution possible and makes "large" files.. so you need a lot of disk space for fairly long captures. But after that you can use tools like Avisynth to good effect, the results will be the best possible and very good. After the video has been corrected, then you can compress it down to MPEG2 or something else for burning to DVD or Bluray or saving to a smaller hard disk file.. the smaller compressed version is called the "Distribution Cut" or version.. for consumers.. but really that process, from Large files to Corrected files to Final compressed files is the best work flow.. because then even the smaller compressed files look stunning and don't carry any of the noise and defects that were present in the original captured video. Its a long workflow.. it takes time.. fixing and rendering takes time.. but you have to invest that time if you want a really good result. Some people get scared by the Large capture files.. and just want an easy one step capture to DVD and hands-off touchless approach. They don't plan to watch the video.. they don't want to be bothered with monitoring the capture or fiddling with correcting it.. or editing it down to remove commercials or turn it into a proper home movie with titles and menus.. thats all fine.. but then they should have probably just went with a DVD recorder rather than tried to do it on a shoestring budget with a usb capture dongle and inadequate pc. |
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Thanks for the summary. I spoke to the professional who converted it and he said the same things that you cited, mainly that there are two reasons for why it looks like that, since this tape is a dub of the original which is no longer available. One is ringing, which U Matic tapes are known for. Older U Matic machines did not have a filter to remove the ghosting of edges, only later ones.
Second is due to cross modulation when a tape was copied using composite rather than dub connectors. Current TBC do not cross modulate due to their digital comb filter, but back then the decks would mix the luminance and chroma values, causing what is seen. I have attached a quick sample of what the problems in the video are. If anyone can tell me what I need to fix, I would appreciate it. |
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Hi Winsordawson,
I have attached a AVIsynth processed AVI of your MP4 file. I think I may have blurred the chroma somewhat. The noise in the clip is not entirely random as it partially consists of wavy vertical lines. These lines could probably be better removed with an FFT frequency filter ( and I haven't worked out how to do this for video yet). I have probably overdone the noise reduction whilst trying to remove the vertical lines. Also Sanlyn may know how to remove the overshoot and rainbowing on the LP record text. |
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Right now I have 7 nightmare tapes and could use a visit from an outside guru who knows a lot more than I do, LOL! Quote:
The best Avisynth learning source for starting is project threads in forums like this. Those posts go back for years. During the past few months there were quite a few detailed discussions. I came up with a list of sample threads that go into detail about some difficult and/or ugly videos, so when you have time you might browse some of these posts: A bunch of restoration samples in the thread "Video capture workflow, some final questions?", post #10 and post #11 Check out http://www.digitalfaq.com/forum/vide...restoring.html, posts #2, #4, #6, #8. post #6 with notes on correcting bad levels in YUV and RGB from underexposure and backlighting: http://www.digitalfaq.com/forum/vide...html#post50797 post #3 has Avisynth script details and some download links: http://www.digitalfaq.com/forum/video-restore/9135-improve-video-avisynth.html#post57143 There are some older details ("Information Overload") that combine Avisynth and VirtualDub in the thread at http://www.digitalfaq.com/forum/vide...html#post42315, posts #16, #17, #19, and #20. Quote:
You're right: other than cut-and-join, transitions, timelines, and some so-so encoding, you can't do much restoration with Adobe. That's not what it's designed to do. Premiere does have excellent color controls (most users have no idea what to do with them, as your mp4 sample might indicate). But it resizes poorly, does sloppy color conversions, and doesn't deinteralce or work well with telecine. For getting into a video's innards and framework, editors are no competition for the combination of Avisynth and Virtualdub. To do better you'll have to go for that second mortgage, cash in your lottery winnings, and start designing your own computers as Disney and George Lucas have. Quote:
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I've no idea why anyone would go for a 960x540 frame unless it was really late at night and their medication wore off. Do you know of any particular reason for it? Not even YouTube would accept it, so I encoded my attached mp4 effort at 1080x720 -- not a good idea with SD sources, but YouTube doesn't have quality-focused requirements, so what can one do?. Quote:
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Going Way back with Windows 3.1 and DOS when users started defying fate by meddling with early digital video, an old addage popped up again and again: Garbage In = Garbage Out, a dictum from which there is no known escape. But the video does have its uses for experimentation. For most of the noisy background maggots and the dropouts I used the median filter FixRipsP2 which has been referenced in several threads and is mentioned in the sample tutorial links I posted earlier, and added some help from ReplaceFramesMC2 and RemoveSpotsMC. The chroma cleaners and de-shimmering parameters of QTGMC in progressive repair mode did some of the smoothing work, and TTempSmooth did a little more. I actually made over a dozen versions of this critter with many multi-part scripts and some VDub filters. The versions ranged from names with A+number in the filename to C+Number. The B's seemed best, if I can use that word. My two posted versions were chosen by the eeny-meeny-miny-moe method. The "BD1" is sharper but noisier with lots of crawling bugs in the background. That one was partially tweaked with NeatVideo. "BD2" used TTempSmooth -- less noise, but less of everything else. Both are 1280x720. I think they would look better at their original 720x480 size. Newbies just don't get it that deinterlacing and resizing are destructive processes with a cost. I have to admit, having seen a lot of bad digital video and dumb mistakes over many years, that this video is an eye-opener. I seriously doubt that Premiere Pro even at its least favorable defaults could output damage like this unless it's done deliberately and maliciously, on purpose. It's a level of creative devastation that's truly impressive. |
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However, given the drinking habits of a lot of bands, keeping the skin color the way it is maybe more accurate :D Quote:
Also, I usually do not care about broadcast safe colors, because this is mainly intended for the web. Does NeatVideo come with Avisynth or it has to be purchased like with Premiere? Quote:
I have attached another version using MPEG Streamclip at 75% quality. It has not been corrected in any way. |
It not even deinterlaced properly (or interlace tags missing if "pic structure" used in h264)
basically that's what you need: ( to be improved) Code:
LWLibavVideoSource("sampleStreamclip75%.mp4") |
Thanks for updating me on some of my assumptions about the original mp4 sample.
The later sample has the same problems, namely that lossy codecs aren't designed for re-encoding or restoration to begin with. I don't know where people get the idea that they are. Sometimes it's interesting to play around with them but, really, the results never look clean and it's a lot of unnecessary work and over-filtering. I see that you don't actually have a lossless original, but re-encoding an already lossy sample isn' the way it's done in Windows. Re-encoding is bypassed for cleanup work using tools designed to extract a decoded version of the core video without taking another quality hit. Once you're free from the limitations with Macs you'll find an entirely different world of tools and processing. For example, there are dozens of deinterlacers, of varying quality and specialization. Here is a comparison video of 4 of them, including the popular TempGaussMC, which has been improved into the plugin known today as QTGMC: stockholma_0-520_q3_yadif_mvbobmod_tgmca4_tdtmm.avi. Quote:
Different users handle color differently. Color and input levels are analyzed and adjusted on both the YUV and RGB level. In each case, different adjustments and results are possible. Most Avisynth denoising and repair is done in YUV, especially in the original, unmodified YUV as captured from analog or as copied from DV. Many defects such as dot crawl, mosquito noise, and chroma blotches are best addressed in YUV before any RGB conversion or other encoding. It's also best to adjust video levels and chroma values in YUV before going to RGB. When Adobe mentioned broadcast-safe color they refer to RGB display results. Perhaps you can visualize that YUV in the range of y=16-to-235 is expanded in RGB to RGB 0-255. RGB can't display anything darker than RGB=0 (y=16) or brigher than RGB=255 (y=235). YUV and RGB values below and/or beyond that range are either clipped (discarded) or distorted into pure noise, either by the encoder or the display. YUV and RGB color are stored differently and behave differently. If you don't mind distortion, then apparently you don't mind the widespread and ugly telltale results of crushed darks and clipped brights so prevalent in the internet's worst, endless examples of noob carelessness and ignorance. If that sounds harsh rest assured that because of those properties neither I nor a real professional would ever advise the owner of family or prized videos to turn their work over to someone who knows so little about basic video behavior. The data that gets clipped and lost is not recoverable. Signal levels and denoising affect color and perceptions of color in many ways. For that reason most of my color work is done in stages, in both YUV and RGB. For most forum quickies I always use Avisynth's and VirtualDub's extensive color controls mainly because I can include filter types and values in forum posts for others to use. Not everyone can afford the ColorFinesse and AfterEffects I often use for my own projects, and TMPGenc's encoders have some nifty YUV and RGB controls. Premiere Pro isn't something I have, since I never had any use for it. DaVinci sounds pretty fancy until you discover the absurdity that it can 't work with losslesss codecs. Avisynth and Virtualdub have YUv and RGB 'scopes and other graphs and controls that are similar to those in other apps. There are color things you can do with Avisynth/VirtualDub that can't be done with Adobe, and vice versa, and things you can do with either. There are plenty of reasons for working with both. I hate color wheels. I tend to go for more precise curves plugins. Quote:
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Prepare an out-of-spec video for web mounting that exceeds RGB 0-255 on display. Let us know what happens. Youtube is flooded with 'em. They're ugly and they look like mistakes. Don't knock CRT's. They're still used today in DVD and BluRay mastering and in Europe, where image quality is more of an issue than over here. |
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I'm afraid you still don't get it with YUV and RGB. Maybe someone else can give you a better explanation, I don't seem to be helping you.
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