[FFmpeg-devel] [PATCH] sws flags for ffmpeg

[Ivo]

On Tuesday 22 May 2007 07:32, mark cox wrote:
> > [...]
> >
> > > +static void opt_sws_type(const char *arg) {
> > > +    struct sws_flags_list sws_type_list[] = {
> > > +        { "fast_bilinear",      SWS_FAST_BILINEAR },
> > > +        { "bilinear",           SWS_BILINEAR      },
> > > +        { "bicubic",            SWS_BICUBIC       },
> > > +        { "experimental",       SWS_X             },
> > > +        { "neighbor",           SWS_POINT         },
> > > +        { "area",               SWS_AREA          },
> > > +        { "bicubic_bilinear",   SWS_BICUBLIN      },
> > > +        { "gauss",              SWS_GAUSS         },
> > > +        { "sinc",               SWS_SINC          },
> > > +        { "lanczos",            SWS_LANCZOS       },
> > > +        { "spline",             SWS_SPLINE        },
> > > +        { NULL,                 0                 }
> > > +    };
>
> Is it possible to add a 'none' option so that the regression tests will
> pass when swscale is used?

I believe the reason the regression tests fail is that the colourspace 
conversions of swscale do not always match imgconvert. Some are more 
accurate, others are not. For example, one could 'upgrade' a 5-bit 
R-component to 8-bits by just doing R<<=3; or one could do R<<=3; R+=R>>5; 
The former is faster, the latter is more accurate. The algorithms in 
libswscale are not always exactly the same as they are in imgconvert.

I don't think the regression tests fail because of scaling issues, only 
because of colourspace conversions. And if there is any scaling involved in 
the tests, we should use an swscaler that matches imgresample, although I 
am not sure if that is possible.

--Ivo