[XviD-devel] Cartoon mode

[Michael Militzer]

Hi,

Quoting Christoph Lampert <chl at math.uni-bonn.de>:

> 
> Hi,
> 
> with all the new and upcoming option, we should maybe bundle
> our knowledge into some "Presets" for the GUI. Instead of 
> suggestions like "quarterpel might help, but not always, depends on the
> input material" (which is absolutely right), we might come up with 
> good presets for the most frequently encoded material. 
> They don't have to be perfect. Just good.

yes, it would be really great to have default settings (or automatic mode or 
whatever), that would give good results for all kinds of input material. I'm 
still wondering why Qpel is sometimes worse and often better than halfpel. I 
have an idea and I'm currently investigating this.

BTW: Could someone provide a clip where qpel performs really bad? At best a 
clip where for a fixed quant encoding qpel produces bigger sizes and lower 
PSNR. This would be helpful since most of my clips seem to be qpel friendly ;-)
 
> a) General natural video   <--- everything "real"        
> b) Action                  <--- explosions, fast movement
> c) Cartoons/Anime          <--- typical: black lines, large 
>                                 unicoloured areas.
> 
> Did I forget anything? 
> 
> What's your suggestion of settings for these when it comes to 
> Bframes, QPel, VHQ, etc. ? About GMC you can forget for the moment, that's
> going to be rewritten during the next few days. 

well, I still hope to find a way to make Qpel always better than halfpel. Also 
it should be possible to tweak the dynamic b-frame decision to achieve 
reasonably optimized b-frame placement (I think rate-distortion optimizations 
may not reflect subjective quality well: so, a clip with b-frames might look 
better than one without even though overall PSNR is lower...)

BTW: cartoon mode. I've thought about it and when we consider that a frame of 
a "normal" cartoon is rather simple (solid colored areas, some sharp lines), I 
think it should be possible to well "reconstruct" the original image also from 
an image distorted by compression artifacts. This leads to the idea that a 
special postprocessing method could be helpful for cartoons. "Cartoon mode" in 
XVID could then simply mean to write a "cartoon=yes" flag into the user data of 
the bitstream that then indicates that the decoder should use a special cartoon 
postprocessing mode...

bye,
Michael