[Ffmpeg-devel] swscaler integration

[Dieter]

In message <44185183.7070207 at mediaxim.be>, Michel Bardiaux writes:
> Dieter wrote:
> > 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?

You could have a program crop_scale_pad which calculates the arguments
and calls the individual crop, scale, and pad programs.