[Ffmpeg-devel] Bug in libavcodec/x264.c?

Luca Abeni lucabe72
Thu Feb 2 12:23:47 CET 2006

Hi all,

in libavcodec/x264.c I see
    x4->params.rc.i_qp_min = avctx->qmin;
    x4->params.rc.i_qp_max = avctx->qmax;
    x4->params.rc.i_qp_step = avctx->max_qdiff;

But... qmin & qmax defaults are 2 & 31, whereas i_qp_min & i_qp_max
defaults are 10 & 51... So, I suppose i_qp_min/i_qp_max use a different
scale respect to qmin/qmax?

The result of this is that using default parameters h264 rate control
does not work very well in ffmpeg (if I encode mpeg4 video, it always
matches the target bitrate, but if I try encoding h264 I often get a lot
of VBV underflows and the final bitrate is wrong).

So, how can I correctly convert qmin/qmax values in i_qp_min/i_qp_max

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