[x264-devel] rate control for static macroblocks

[Anne Aaron]

2008/6/10 Anne Aaron <anne at dyyno.com>:
> I'm running x264 with CBR rate control under a few seconds of VBV buffer
> constraint,  on content where some rows of macroblocks are perfectly static
> (zero distortion from the previous frame co-located macroblocks). For these
> macroblocks,  the satd is zero so their statistics are not included when
> update_predictor(...) is called. Aside from divide by zero, any reason for
> when (var <  10), update_predictor() returns right away?

ratecontrol.c, line 1289.
Is there a reason that the statistics of low satd macroblocks are not included in the predictor?

> The code base that I tested is actually a few months old so I don't have adaptive quantization.
> After reading more I realized that the commit last week on VBV improvements should help the issue I'm encountering:
> http://git.videolan.org/gitweb.cgi/x264.git/?a=commit;h=7331ea4e381898421a1a908ed57f73126faacd36
> The new check in x264_ratecontrol_mb( x264_t *h, int bits ) for updating the QP after a row will suppress the QP increase.

ratecontrol.c, line 943