[FFmpeg-devel] [PATCH] add ME_T/ESA to avcodec.h

[Robert Swain]

2008/6/7 Michael Niedermayer <michaelni at gmx.at>:
> On Fri, Jun 06, 2008 at 07:25:24PM -0700, Baptiste Coudurier wrote:
> [...]
>> 2) adding a way to override AVOptions range for qmax etc.. which needs
>> to be hardcoded because user has no business saying that qmax max value
>> for mpeg-2 is 7821637.
>
> true
>
>
>> Mainly because bumping default max value to 1024
>> would require every codec supporting qmax to check if value is valid.
>
> I see the problem, i dont know which solution is best but
>
> qmax in mpeg2 depends on the use of non linear quantizer IIRC (unless i
> have the place of where the max is applied wrong ...)
> then most options depend on the profile & level, some might depend on
> the pixelformat 420 vs. 422 vs. 444
>
> So simple per codec ranges are not enough at all ...

Indeed. Possibly even more flexibility is needed. For the x264
defaults, some values depend on other values if they are to match the
x264 CLI. We may not do this but, for example, rate tolerance in x264
is expressed as a multiplier of the bit rate I think and by default it
is set to 1.0. To imitate that behaviour in FFmpeg one has to set -bt
equal to the specified bit rate (if there is one). I don't think this
can be done in your presets code, can it?

Rob