[x264-devel] Fwd: x264 rate control

[Jason Garrett-Glaser]

On Fri, Feb 1, 2013 at 12:59 AM, eloise vidal <eloise.vidal at gmail.com> wrote:
> Hey Jason,
>
> You can download 2 sequences and a summary of my observations at :
> http://www.digigram.com/DOWNLOADS/EVI
> login : ftp_download
> pwd : SMD2qcgY

"and it spends all the sequence (200 frames) to increase the number of
bit per frame to reach the target bitrate." is an incorrect
description of what is happening here.  CBR doesn't have a target
bitrate.  Ratecontrol is just reacting slowly in this case -- you can
see it takes about 24 frames for ratecontrol to start reacting...
which is not coincidentally the number of threads!

As far as I can tell, the issue is almost entirely in the first 24
frames of the video, and the encoder is largely fine after that.

Again, might I suggest using fewer threads?  That, or submit a patch
to improve the start of encoding with 1-pass CBR ratecontrol with
insane thread counts, or at least figure out where the problem is
occurring (updated predictors need to be propagated to past threads,
maybe?)?

Jason