Jan 25 2014

A year of Overmixing

Category: Overmix,Programs,SoftwareSpiller @ 01:54

It is now about a year ago since I started this project, and not in my wildest dreams I would have imagined how much work I have put into this by now. So here is a quick overview of my progress.

(Overmix is now located at github: https://github.com/spillerrec/Overmix, download here: https://github.com/spillerrec/Overmix/releases )

Automatic aligning

While zooming and rotating is not supported (yet at least), horizontal and vertical movement is rather reliably detected and can be done to sub-pixel precision. Sub-pixel precision is rather slow and memory intensive though, as it works by image upscaling. Still needs some work when aligning images with transparent regions though, and I also believe it can be made quite a bit faster.


Noise is removed by averaging all frames and works very well, even on blue-ray rips. However since I have not been able to render while taking sub-pixel alignment into account, it blurs the image ever so slightly.

10-bit raw input and de-telecine

I have made a frame dumper to grab the raw YUV data from the video streams, to ensure no quality loss happen between video file and Overmix. This actually showed that VLC outputs in pretty low quality, and appears to have some trouble with Hi10p content and color spaces. Most noticeable however is that VLC uses nearest-neighbor for chroma-upsampling, which especially looks bad with reds. Having access directly to the chroma channels also opens up for the possibility of doing chroma-restoration using super resolution.

I have made several tools for my custom “dump” format, including the video dumper, Windows shell thumbnailer (vista/7/8), QT5 image plugin and a compressor to reduce the filesize. They can be found in their separate repository here: https://github.com/spillerrec/dump-tools

De-telecine have also been added, as it is necessary in order to work with the interlaced MPEG2 transport stream anime usually is broadcasted in.


Using deconvolution I have found that I’m able to make the resulting images much sharper, at the expense of a little bit of noise. It appears that anime is significantly blurred, perhaps because of the way it have been rendered, or perhaps intentionally. More on this later…

TV-logo detection and removal

It works decently as shown in a recent post and can also remove other static content such as credits. I have tried to do it fully automatically, but it doesn’t work well enough compared to the manual process. Perhaps some Otsu thresholding combined with dilation will work?

I’m intending to try doing further work with this method to see if I can get it to work with moving items, and doing the reverse, separating the moving item. This is interesting as some panning scenes moves the background independently of the foreground (for faking depth of field).

Steam removal

Prof-of-concept showed that if the steam is moving, we can chose the parts from each frame which contains the least amount of steam. Thus it doesn’t remove it completely, but it can make a significant difference. The current implementation however deals with the colors incorrectly, which is fixable, but not something I care to do unless requested…


Some scenes contains a repeating animation, while doing vertical/horizontal movement. Especially H-titles seems have much of this, but can also be found as mouth movement and similar. While still in its early stages, I have successfully managed to separate the animation into its individual frames and stitch those, using a manual global threshold.

I doubt it would currently work with minor animations, such as changes with the mouth, noise would probably mess it up. So I’m considering investigating other way of calculating the difference, perhaps using the edge-detected image instead, or doing local differences.