[FFmpeg-devel] DNxHD and qmax

Joseph Artsimovich joseph at mirriad.com
Thu Feb 2 10:55:21 CET 2012

On 02/02/2012 03:52, Michael Niedermayer wrote:
> On Wed, Feb 01, 2012 at 11:13:46AM +0000, Joseph Artsimovich wrote:
>> The default value for qmax in FFMpeg is 31, with FFmpeg's DNxHD
>> encoder actually enforcing it. Now, enforcing qmax in a CBR codec
>> makes no sence, as no one wants encoding to fail just because the
>> minimum allowed quality specified by qmax doesn't fit into the given
>> bitrate. The DNxHD specification actually specifies 1024 as the
>> maximum quantization scale factor.
>> Should I submit a patch making the DNxHD encoder ignore qmax?
> the default value can be overriden, see libx264.c for example
> that seems more flexible as the user then still can set it if he
> really wants to
That's easy to implement, however I would rather not give users ability 
to set qmax for CBR codecs, as it means giving them a rope to hang 
themselves on. I don't see any other uses for that feature.

Joseph Artsimovich
Senior C++ Applications Developer
MirriAd Ltd

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