[MPlayer-advusers] 3-pass encoding bug or design flaw?

[Zoltan Hidvegi]

When encoding a video which has a significant section that is
completely black with ffmpeg mpeg4, the 3-pass encoder pushes up the
quantizers to 31 in the black region.  This only happens in the third
pass for some reason.  The problem is that it does not really save any
bits, and when some more complex content follows the black region, it
takes a few seconds until the quantizers are reduced back to sane
levels, and the video looks really horrible during that time.  I have
tried to set vqblur=0.0 and I've tried to use vrc_override, but
neither helps.  It seems that vrc_override is completely ignored in
the third pass, and vqblur worked exactly opposite as I expected,
after setting vqblur=0.0 it took a longer to reach q=31 in the blank
region, but there was no change in the rate of decrease of the
quantization levels after the blank region.  One solution would be is
to avoid pushing up the quantization at blank frames, but if an
automatic solution is difficult, respecting vrc_override would help
too.

Thanks,
Zoli