[FFmpeg-devel] Strange qmax behaviour with mpeg2

Michael Niedermayer michaelni at gmx.at
Wed Sep 12 11:41:47 CEST 2012

On Wed, Sep 12, 2012 at 09:57:41AM +0100, Joseph Artsimovich wrote:
> On 11/09/2012 16:59, Michael Niedermayer wrote:
> >On Tue, Sep 11, 2012 at 12:02:14PM +0100, Joseph Artsimovich wrote:
> >>Hi,
> >>
> >>When encoding IMX 30 content (I-frame only mpeg2 at fixed bitrate) I
> >>noticed ffmpeg produces lower quality output than other encoders.
> >>Digging deeper, I found strange behaviour of qmax parameter with
> >>mpeg2video encoder that I can only explain away as a bug.
> >>
> >>Before explaining further, here is my command line:
> >>ffmpeg -i input.mov -vtag mx3p -vcodec mpeg2video -r 25 -pix_fmt
> >>yuv422p -minrate 30000k -maxrate 30000k -b:v 30000k -intra -flags
> >>+ildct+low_delay -dc 10 -intra_vlc 1 -non_linear_quant 1 -ps 1 -qmin
> >>1 -qmax 8 -top 1 -bufsize 1200000 -rc_init_occupancy 1200000
> >>-rc_buf_aggressivity 0.25 -an out.mov
> >should be fixed

> I see this behaviour with the latest ffmpeg from git.

in that case your input file is needed because the issue is fixed
with matrixbench_mpeg2.mpg

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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