[MPlayer-dev-eng] Re: [PATCH] New video filter: deblendlogo

[D Richard Felker III]

On Thu, Feb 24, 2005 at 01:27:23PM -0800, Trent Piepho wrote:
> On Thu, 24 Feb 2005, Oded Shimon wrote:
> > Done.
> > 
> > Adds YV12 support to this deblendlogo filter.
> > Almost a complete re-write of the original filter.
> > Unlike original filter, it accepts only a filename, no offset, and the png 
> > image has to be the same res as the video frame.
> 
> You could try premultiplied alpha to make it faster.  You inner look looks like
> this:
> 
>   pic_plane[x] = CLIP((pic_plane[x] - tmpl_plane[x] * alpha) / (1.0 - alpha));
> 
> You can calculate tmpl_plane[x] * alpha once after the image is converted to
> YV12 and just store it instead of the original image.  The same with 1-alpha,
> just store it instead of alpha.

if you premultiply and convert back to 8bit samples, a bit of
precision is lost. don't know if it will be visible. converting
everything to use fixed point, and keeping the logo image as 8.8 fixed
point would probably make things a lot faster and keep all the
accuracy.

rich