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

[Joey Parrish]

On Wed, Feb 23, 2005 at 01:21:28AM +0200, Oded Shimon wrote:
> It's worse than I thought. :/ It's not just the green line, the entire image 
> has gone down in quality - it's as if someone used nearest neighboor scale to 
> half the size, and then again to twice the size. (i.e., 75% of the pixels 
> were completely lost.)

That sounds exactly like RGBA->YV12->RGBA.
You scale the chroma to half-size...

> I did find this, using these params, there is no quality defects, no green 
> line problem, nothing. Absolute perfection:
> -vf 
> scale=,format=fmt=rgba,deblendlogo=730:409:chan3-logo.png,scale=,format=fmt=yv12
> 
> If I get some time I might look into it and fix the filter. Generally color 
> converting at all is (a little) lossy, so if it's possible in some way to 
> make this filter work in YUV without converting anything, it would be 
> awesome. I think it is possible, as far as I can tell, alpha works just as 
> well on YUV as it does on RGB. All you need to do is first convert the input 
> png image to YUV instead of RGB (and store the alpha separately or 
> something).

I agree.  Using swscale inside the filter is a BAD idea.  You should
either support it or let the automatic conversions handle it.  Faking
YV12 support is not helpful at all.

--Joey

-- 
"I eat donuts for dying children." --Andrew