Averaging preprocessor

Hi,

I've been thinking of a little preprocessing method that would make video=
=20
material (and especially animation) more efficient to compress:

  a) divide the stream into blocks
  c) for each block, decide if the contents is still essentially
     the same as in last N frames (i.e. nothing has occluded the
     picture, picture has not moved and there has not been a cut
     in the video)
  d) if so, add block's values to those last N frame's
  e) if not, calculate an average and use it to replace all
     blocks that contributed to it

If done well, this should reduce noise significantly from mostly static f=
rames=20
and thus reduce unnecessary re-encoding of blocks that didn't really chan=
ge.=20
It of course requires an extra pass, or if applied in real time, a buffer=
 for=20
the N frames.

Step d) is obviously the most difficult one to get right. The block shoul=
d=20
probably be pretty large to filter out small local noise and they could=20
overlap (+ be partially alpha blended in step e) to prevent sharp borders=
=20
between them.

Of course, it would also be nice to take small motion (camera shaking etc=
)=20
into account while averaging, but I don't know if it could be made accura=
te=20
enough - even though the blocks would be larger than in usual MC.

Anyone tried such filtering before?

- Jarno
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