[FFmpeg-devel] DNxHD and qmax

Baptiste Coudurier baptiste.coudurier at gmail.com
Fri Feb 3 08:57:57 CET 2012

On 2/2/12 11:38 AM, Michael Niedermayer wrote:
> On Thu, Feb 02, 2012 at 09:55:21AM +0000, Joseph Artsimovich wrote:
>> 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.
> hmm, the encoder could try to honor the qmax and only if that fails
> ignore it to achive the bitrate requirements
> anyway, unless baptiste disagrees iam happy to apply whatever patch
> you consider to be the correct solution.

Let the user specify qmax.

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