[MEncoder-users] "requested bitrate is too low." in 2-pass x264 encoding

[Tom Hicks]

On Thu, Apr 8, 2010 at 8:49 AM, 呂建林 <x4base at gmail.com> wrote:

> Hello, everyone.
> I tried to encode a file to the x264 codec
> These were what I typed:
> mencoder -nosound  -ovc x264 -x264encopts pass=1:bitrate=2000 -o
> test.mp4   -endpos 10 shadow.flv
> mencoder -nosound  -ovc x264 -x264encopts pass=2:bitrate=2000 -o
> test.mp4   -endpos 10 shadow.flv
>
> my mencoder and libx264 were compiled from the svn and git version
> ,respectively
>
> the 1st-pass finished successfully. but in the 2nd pass , it
> complained "x264 [error]: requested bitrate is too low. estimated
> minimum is 9 kbps".
> The same thing kept happening even if I set the bitrate=20000000
> This is quite strange.
>
>
> The following is what I tried:
>
> I did a little code tracing and I found that in the function
> init_pass2 in encoder/ratecontrol.c of the libx264 code,
> there was
>  if( all_available_bits < all_const_bits)
> {
>        x264_log( h, X264_LOG_ERROR, "requested bitrate is too low.
> estimated minimum is %d kbps\n",
>                 (int)(all_const_bits * rcc->fps / (rcc->num_entries *
> 1000.)) );
>        return -1;
> }
>
> The value  [all_available_bits] is calculated from
> h->param.rc.i_bitrate * 1000. * duration.
> Also , the value of  [duration] is summed from
> rcc->entry[i].i_duration , which , in the log file divx2pass.log, seem
> to be 0 for each i.
> Is it common for i_duration to be always 0?
> So it seems that the expression all_available_bits < all_const_bits is
> always true, and therefore mencoder keeps complaining
>
> Did I misunderstand anything ?
> If
> Or I just gave  some wrong options to mencoder?
>
> Thanks for your attention.
>
> my system info:
> 2.6.30.10-105.2.23.fc11.x86_64
> MEncoder SVN-r31027-4.4.1
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> MEncoder-users at mplayerhq.hu
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I use the binaries from
http://sourceforge.net/projects/mplayer-win32/files/MPlayer%20and%20MEncoder/revision%2031027
and
got the same error and I know no one here supports them.

I just switched to r30945 instead and the problem went away.  I can't
compile it myself to check right now but whatever happened seemed to be
about then.

~Tom