[Ffmpeg-devel] video post processing filters

Nagendra Rao nag.nagendra
Thu Apr 21 05:24:00 CEST 2005

hai all,
 this is nagendra, a student from National Institute OF Technology Calicut,
India.i am having problem with postprocessing that was included in ffmpeg 
project.i've posted three-four times regarding the same issue without 
getting any reply hope this time some one will attend my request.
after going thru the code i felt deblocking and deringing have been 
implemented according to ISO/IEC spec.but i've confusion at threshold 
ISO/IEC specs says that for simulation *THR1=2* AND *THR2=6* but in ffmpeg's 
"libavcodec\libpostproc\postprocess.c" these r defined as
  THR1 ------------ * dcThreshold*= dcOffset*2 + 1; 
 where dcOffset= ((nonBQP*baseDcDiff)>>8) + 1; (baseDcDiff=32 large=>more 
 THR2 ------------ * flatnessThreshold* (default=32 less=> more deblocking)
 could anybody pls give a link that describes the theory behind selecting 
these threshold values.
 what is "*nonBQP*" ? if i do not use B frames at all will it be same as *QP
* ??
 similarly deringing filter also seems to be implemented from ISO/IEC spec 
but i can't able to understand the code at index aquisition part i think its 
been implemented differently from iso/iec spec,i don't know if iam wrong. 
could anybody pls tell me the significance of *deringThreshold *being 
selected as *20*
*i hope this time i'll get a solution or atleast a reply to my mail*
thanx in advance
Nagendra Rao
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