7.1.6. Filtering
Learning how to use MEncoder's video filters is essential to producing good encodes. All video processing is performed through the filters -- cropping, scaling, color adjustment, noise removal, sharpening, deinterlacing, telecine, inverse telecine, and deblocking, just to name a few. Along with the vast number of supported input formats, the variety of filters available in MEncoder is one of its main advantages over other similar programs.
Filters are loaded in a chain using the -vf option:
-vf filter1=options,filter2=options,...
Most filters take several numeric options separated by colons, but the syntax for options varies from filter to filter, so read the man page for details on the filters you wish to use.
Filters operate on the video in the order they are loaded. For example, the following chain:
-vf crop=688:464:12:4,scale=640:464
will first crop the 688x464 region of the picture with upper-left corner at (12,4), and then scale the result down to 640x464.
Certain filters need to be loaded at or near the beginning of the filter chain, in order to take advantage of information from the video decoder that will be lost or invalidated by other filters. The principal examples are pp (postprocessing, only when it is performing deblock or dering operations), spp (another postprocessor to remove MPEG artifacts), pullup (inverse telecine), and softpulldown (for converting soft telecine to hard telecine).
In general, you want to do as little filtering as possible to the movie in order to remain close to the original DVD source. Cropping is often necessary (as described above), but avoid to scale the video. Although scaling down is sometimes preferred to using higher quantizers, we want to avoid both these things: remember that we decided from the start to trade bits for quality.
Also, do not adjust gamma, contrast, brightness, etc. What looks good on your display may not look good on others. These adjustments should be done on playback only.
One thing you might want to do, however, is pass the video through a very light denoise filter, such as -vf hqdn3d=2:1:2. Again, it is a matter of putting those bits to better use: why waste them encoding noise when you can just add that noise back in during playback? Increasing the parameters for hqdn3d will further improve compressibility, but if you increase the values too much, you risk degrading the image visibly. The suggested values above (2:1:2) are quite conservative; you should feel free to experiment with higher values and observe the results for yourself.
Gerade das Einstellen der Farben ist ne echte Herausforderung meiner Meinung nach.