[x264-devel] rate control for static macroblocks

[Alex Giladi]

Anne,
Which revision of x264 are you using? Are you using the multithreaded mode?
Alex.

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?
>
>
>
> This may be the cause of one artifact that I am observing --  After a row of
> static macroblocks, the rate control tends to think that it will overproduce
> for the remaining rows and therefore increase the QP for the remaining rows.
> In fact, when the entire frame is static, the QP of the frame is very high.
> Since the frame is static, this has no detrimental effect on the frame
> itself. However, since the QP of the  I frames are based on the average of
> the previous P frames, the I frames tend to have low quality and beating is
> observed . Anyone has had similar observations or explanations?
>
>
>
> Anne
>
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