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<p class=MsoNormal>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? <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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? <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Anne<o:p></o:p></p>
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