[x264-devel] [patch] I-frame bit reservation for single pass VBV

[Jindrich Makovicka]

Hi,

the attached patch (consider it rather a suggestion, as I am not very
familiar with x264 internals) adds a buffer reservation option for
I-frames. The rationale is that a true CBR encode
(bitrate=vbv_maxrate) can produce considerable flickering, because
there are not enough bits available in the buffer when an I-frame is
encoded, and so the I-frames and a few subsequent P-frames have lower
quality.

The patch adds a "vbv-ireserve" option, which specifies how many bits
should be reserved for the next I-frame, as a multiplier of the size
of the last I-frame. This is still far from being perfect, but it
works well in slow scenes where the flicker is most apparent. I used
the obvious choice of vbv-ireserve=1, but it might be worth trying a
bit more or less.

With default value of vbv-ireserve (=0), the rate control behavior is
unchanged from the current state.

Regards,
-- 
Jindrich Makovicka
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ireserve.diff
Type: text/x-patch
Size: 6490 bytes
Desc: not available
Url : http://mailman.videolan.org/pipermail/x264-devel/attachments/20061101/37745292/attachment.bin