[Ffmpeg-devel] swscaler integration

Michel Bardiaux mbardiaux
Wed Mar 15 18:40:19 CET 2006

Dieter wrote:
>>>But now I am thinking about the "video filter layer" mentioned by
>>>Michael in one email about cropping and padding.
>>>Maybe the best thing to do is to introduce a "video filter" library, and
>>>move swscaler into it.=20
>>Looks pretty as concept.
> Ken and Dennis did filters 30+ years ago.  Just change from grep and cut to
> video/audio filters:
>    ... | crop | scale | pad | text_overlay | aknobs | vknobs | ...
> text_overlay adds subtitles, closed caption, clock, frame counter, ...
> aknobs adjusts volume, bass, treble, ...
> vknobs adjusts brightness, contrast, saturation, ...
> Smaller programs are easier to understand, write, debug, ...
> If aknobs doesn't do what you want, plug in octive_equalizer instead.
> If you have a SMP machine, you automatically get parallel processing.
> Filters with different licenses can work together in peace.
Also: it is not difficult to design a command language so that the 
control of filters is outside the arguments of the ffmpeg command line.

What bothers me is rescaling with required aspect ratio, like a DVD 16/9 
NTSC to a PAL VCD: there is an optimum combination of crop, pad and 
scale that will achieve best effect. It is too complex to impose on the 
user the task of computing the parameters. So, decoupling crop/scale/pad 
may not be the best solution after all. But maybe that would have to be 
*another* filter?

Michel Bardiaux
R&D Director
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