[FFmpeg-devel] [WIP] rotate filter(s)

[Stefano Sabatini]

On date Wednesday 2010-10-06 16:21:16 +0200, Michael Niedermayer wrote:
> On Tue, Oct 05, 2010 at 09:38:06PM +0200, Stefano Sabatini wrote:
> > On date Tuesday 2010-10-05 14:36:19 +0200, Michael Niedermayer encoded:
> > > On Mon, Oct 04, 2010 at 10:27:29PM +0200, Stefano Sabatini wrote:
> > [...]
> > > > +/**
> > > > + * Interpolate the color in src at position x and y using bilinear
> > > > + * interpolation.
> > > > + *
> > > > + * @param dst_color put here the destination color
> > > > + */
> > > > +static uint8_t *ipol(uint8_t *dst_color,
> > > > +                     const uint8_t *src, const int src_linesize, int x, int y,
> > > > +                     int max_x, int max_y)
> > > > +{
> > > > +    int int_x = x>>16;
> > > > +    int int_y = y>>16;
> > > > +    int frac_x = x&0xFFFF;
> > > > +    int frac_y = y&0xFFFF;
> > > > +    int i;
> > > > +
> > > > +    for (i = 0; i < 3; i++) {
> > > > +        int s00 = src[3 * int_x                + i + src_linesize * int_y];
> > > > +        int s01 = src[3 * FFMIN(int_x+1,max_x) + i + src_linesize * int_y];
> > > > +        int s10 = src[3 * int_x                + i + src_linesize * FFMIN(int_y+1, max_y)];
> > > > +        int s11 = src[3 * FFMIN(int_x+1,max_x) + i + src_linesize * FFMIN(int_y+1, max_y)];
> > > > +        int s0 = (((1<<16) - frac_x)*s00 + frac_x*s01)>>8;
> > > > +        int s1 = (((1<<16) - frac_x)*s10 + frac_x*s11)>>8;
> > > > +
> > > > +        dst_color[i] = (((1<<16) - frac_y)*s0 + frac_y*s1)>>24;
> > > > +    }
> > > 
> > > the >>8 can be avoided by adjusting perecission sanely
> > > the FFMIN doesnt belong in the loop
> > 
> > I can do:
> >       int s0 = ((1<<16) - frac_x)*s00 + frac_x*s01;
> >       int s1 = ((1<<16) - frac_x)*s10 + frac_x*s11;
> > 
> >       dst_color[i] = (((int64_t)(1<<16) - frac_y)*s0 + (int64_t)frac_y*s1)>>32;
> > 
> > Is this what you suggest?
> 
> frac_x >>=6
> frac_y >>=6
> outside the loop

Updated work in progress, with *lots* interface improvements, I have
yet to fix the problems spotted by Michael, also IIRC I seem to
remeber there was a problem with formats for which hsub != vsub (which
are currently disabled).

I'd like to committ the filter, even if we develop a more advanced
affine/prospective filter, since this will be possible more efficient
(no float arithmetic) and more suited to this particular task (and the
filter is laying on ML since too much time IMO).
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