[Ffmpeg-devel] ASP/AVC defaults

Michael Niedermayer michaelni
Wed Dec 7 14:50:34 CET 2005


On Wed, Dec 07, 2005 at 05:38:07AM -0000, Robert Swain wrote:
> Hello all,
> I am interested in spending some time updating the x264 interface to a
> current level. However, along the way it has been noted that some of the
> default values for some parameters are unsuitable not only for AVC, but for
> ASP as well.
> Default value alterations:
> gop_size
> current = 12 (... in ffmpeg.c which overwrites 50 in utils.c)
> proposed = 10 * framerate (for ASP and AVC)

not ok, mpeg doesnt allow >132 updates (inter MBs) or so, either check that
there are not to many colocated inter MBs or set the default GOP <132
and yes iam aware everyone uses 300frame gops in mpeg4 but the defaults
should not violate the spec, not to mention that theres a reason why
that 132 limit is in there ...

> It should be apparent that there is the problem of different default value
> requirements sharing the same parameters. I could add new parameters for
> each codec as necessary (say -asp_qmin and so on) or I could design some new
> method for handling defaults dependent on which codec is selected. I don't
> know which way is better or if there are other, better methods that I
> haven't thought of, but I would appreciate your input to select the most
> acceptable method before I begin.

IMHO -asp_qmin is a silly idea

you should also be carefull not to break any regression tests 
(update regression.sh to avoid checksum changes)


More information about the ffmpeg-devel mailing list