[XviD-devel] 2pass curve compression
Edouard Gomez
xvid-devel@xvid.org
Fri, 9 Aug 2002 19:36:18 +0200
Dirk Knop (dknop@gwdg.de) wrote:
> Hi,
>
> yetserday I talked some time with Foxer about "his" alt CC curve
> compression algorithms.
> In th end, the descriptions can be made a little more understandable in
> a less-technically language:
The code, even if it lacks some comments, is quitly
understandable. When i ported the code for the independant vbr lib,
the code revealed me what it does without too much difficulties. On
the other hand some parameters were obscure... but anyway, i'll try to
make a good document on how the vbr code does the job (could be used
for both vfw and whatever project based on the vbr lib)
>
> I would like to see new default values implemented into XviD [...]
>
I will apply your defaults in transcode too, so every XviD user will
have the same result for the same movie and same set of paremeters :-)
thx
> I'd like to have a linear scaled curve with a high and lowpass, some
> overflow treatment which works like it now works (scene based), and some
> mechanism to prevent too small frames to get quantized more ;) Maybe a
> reaction delay for the oveflow treatment as well.
You could also try to build an heuristic function f(mblocks, ublocks,
iblocks) that would return a hint on how the quantizer should
evolve. The above function should use a sliding window to have both
past (overflow, need to be controled) and future estimation (so we
would know when a scene becomes static or with action). This is just
an idea I had when looking at the code during the lib port. But I know
this heuristic function could help a lot but is rather difficult to
tune.
> Ok, just wanted to share thse results.
Thx
--
Edouard Gomez