[XviD-devel] quantizers table for postprocessing

Michael Militzer xvid-devel@xvid.org
Sun, 29 Sep 2002 16:03:01 +0200


Hi,

> >I've just integrated postprocessing code from Nic's XviD DirectShow
> >filter to ffdshow. It's not very tested yet, but I think it will work.
> >For postprocessing I need quantizer array for decoded frame. As I saw
> >in Nic's sources, he casts xvid handle and accesses the DECODER
> >structure memeber. Would it be possible to integrate some more convenient
> >way of obtaining quantizers into new API?
>
> its possible, but we need to define exactly what the api should
> return. do you just want quantizers? or are dc/ac coefficents also
> useful? i dont know much about post processing.

dc/ac coefficients are important. I sometimes read a paper where an approach
was presented which considered dct coeffs and depending on these varied the
postprocessing filter strength (or decided not to filter at all). This seems
reasonable to me.

> i really think someone should develop a  libpostproc, which takes
> an image + quantizer/coeffs-array, and performs post processing.
> that way, all decoders xvid,ffmpeg,libmpeg2,etc. could benefit.

yes and no. One postprocessing lib for all open-source codecs would be a
good idea, but if we need to consider dct coefficients (and I think we
should) and need to copy the coeffs to an external postproc lib, this could
severely slow down the decoding process...

bye,
Michael