Im trying to encode one of my dvd's and I notice alot of these tiny squares and marks showing up still after all of my filters are used. They move around as the video plays and are quite visible. I find these annoying and would like to be able to reduce or get rid of them without ruining my image I have so far.
I am already using a denoiser, what are these artifacts and how can I reduce or get rid of them?
http://img31.imageshack.us/img31/2774/example2g.png
http://img543.imageshack.us/img543/6730/example7h.png
http://img209.imageshack.us/img209/5610/example6.png
http://img688.imageshack.us/img688/910/example1f.png
http://img210.imageshack.us/img210/378/example3h.png
http://img521.imageshack.us/img521/814/example4x.png
http://img267.imageshack.us/img267/7605/example5i.png
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Last edited by darkdream787; 17th Jan 2012 at 00:29.
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It's quantization of gradients and flat areas, usually from overdenoising, not enough bitrate, unoptimized encoding settings , or some combination of those
Either dithering, adding noise, using weaker denoise settings, using higher bitrate, different encoder settings or some combination of these will help -
What encoder? Use a higher bitrate, add dithering, adjust AQ settings (usually higher strength will help in this case)
Without dithering or noise, most encoders will assign higher quantizer to flat dark areas and gradients, so you get blocky artifacts at low bitrates . AQ redistributes bitrate to those areas, but overdoing it can reduce quality in other areas like edges -
Avisynth and Me-Gui
I remember trying to use dithering a long while back and I could never get it to work.
I can still see those artifacts even when I dont use a denoiser. Could it be the bitrate then? they still seem to show even when I up it to 2000.
they seem a bit less noticeable if I dont use a sharpener at all, but I dont want to take off my sharpen. It looks terrible without sharpen or denoise. -
Are they there before you encode? visible in the script preview ?
If not, then it's your encoding settings (dithering as preprocessing can help too)
Dark areas (eg.shadows) are often assigned high quantizers, because they are deemed to be less important, and not that visible under normal viewing conditions.
Did you also calibrate your viewing setup ? -
Yeah they are there in the script preview but their covered up by tons of noise so you can hardly tell they are there but its also so much noise that it looks horrible. Seeing the artifacts actually looks better to me. You can still see them if you know to look for them in the script preview but the denoiser makes em more visible. at the same time it makes the picture look almost 100% better.
what do you mean by calibrate my viewing setup up and AQ settings?Last edited by darkdream787; 16th Jan 2012 at 21:53.
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Well, if they are visible even before you encode, then it's inadequte filtering . Encoding with any lossy format will make the "blocks" more visible.
what do you mean by calibrate my viewing setup up and AQ settings?
AQ is an encoding setting that redistributes bits to flat, dark areas like shadow gradients, it can help with problems like your screenshots (but won't help much if see problems in the script preview even before encoding) -
if its inadequate filtering what would you suggest using besides dither?
Yeah I have checked the calibration and viewed this on 3 computers and a dvd player. it looks best on the dvd player but on all the computers I can still see them. I saw them most on my computer but I could still see them none the less on the others as well.
Here is what it looks like before ive done anything to it in the preview
http://img207.imageshack.us/img207/8085/example8.png
It needed deinterlaced, had dot crawl, needed denoised and sharpened to me. Last but not least cropped and resized as well.Last edited by darkdream787; 17th Jan 2012 at 00:32.
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Look at the dither thread or flash3kyuu_deband thread for great examples of dithering, especially with animation at doom9
They are essentially adding fine noise through a mask. So areas that need it get more, areas that don't get less (this mean less bitrate required)
Dither filters like gradfun3() use ordered dithering, so the pattern is fixed (also less bitrate required)
Noise or dithering works by either "covering up" defects like blocks, or "forces" the encoder to allocate more bitrate to those areas -
Last edited by darkdream787; 16th Jan 2012 at 22:15.
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I don't know what you mean by "calibration". This is an example of the way a computer monitor should be calibrated:
http://www.tftcentral.co.uk/reviews/eye_one_display2.htm
In any event:
The original already shows signs of oversharpening. Mainly, however, it's too dark and oversaturated to begin with. Your script compounds the problem, oversharpens again, darkens more, and saturates more. You might want to learn learn to work with histograms to analyze images. The histogram below of your posted original image (Photoshop, based on Rec709 video levels) shows crushed blacks climbing up the left-hand side of the histogram and highlights starting to climb up the right-hand side. Reducing contrast and saturation in YUV helps curb this.
[Attachment 10567 - Click to enlarge]
You should make a basic correction for levels in YUV before denoising.Last edited by sanlyn; 21st Mar 2014 at 09:14.
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