[Theora-dev] Fix a bug that causes the encoder to spend way to
many bits on keyframes
pin at medic.chalmers.se
Fri Feb 18 09:49:21 PST 2005
On Thu, Feb 17, 2005 at 11:22:11AM -0800, Aaron Colwell wrote:
> Here is a fix that prevents the encoder from spending too many bits on
> keyframes. The main problem is that the old code computes the target keyframe
> bitrate incorrectly. This causes the code that computes the Q for the frame to
> have to use a much lower Q. This ends up causing a "popping" artifact where
> everything is clear for a keyframe, but gets progressively blurry for each
> successive inter-frame.
I have been looking for the reason of that (or similar) effect.
No one on the list answered when I asked.
Now I tested the encoder with your change, and unfortunately it did not
improve the cases where I see artifacts - still your change looks right,
if I can believe the comments in encoder_toplevel.c.
I see terrible artifacts on "text screens" with e.g.
theora-encoder -a 0 -V 400 -o newref.400.ogg AmelieArchive.mpg
e.g. during the seconds 4 and 5
or very spectacular ones with
theora-encoder -a 0 -V 2000 -o newref.2000.ogg AmelieArchive.mpg
e.g. during the seconds 13-16...
theora-encoder script runs theoraenc which (and the library)
is from today's svn.
Would you - or anybody - comment on my observations?
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