[FFmpeg-devel] Strange qmax behaviour with mpeg2

Joseph Artsimovich joseph at mirriad.com
Wed Sep 12 10:57:41 CEST 2012

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.

> also you should add at least -lmin QP2LAMBDA
Doesn't seem to make a difference.

Joseph Artsimovich
Senior C++ Applications Developer
MirriAd Ltd

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