[FFmpeg-devel] [PATCH]Support 64bit RGB input

[Michael Niedermayer]

On Sat, Mar 03, 2012 at 11:22:13PM +0000, Carl Eugen Hoyos wrote:
> Michael Niedermayer <michaelni <at> gmx.at> writes:
> 
> > > > > Attached patch allows to convert 64bit RGB input.
> > > > 
> > > > LGTM
> > > 
> > > Conversion to RGBA produces (nearly) transparent files 
> > > because A1 and A2 overflow in yuv2rgb_1_c_template if 
> > > input is 0xFF, patch follows inlined:
> > 
> > why do they overflow ? is there some incorrect scaling applied
> > somewhere ?
> 
> rgba64ToA_c() in input.c reads 65535 (=completely opaque), not 
> 0xFF as written above, as alpha value for (the lower part of) 
> the sample from ticket #503, hyscale() in swscale.c calls 
> c->hyScale() which changes the value to 32767, 
> yuv2rgb_1_c_template() in output.c calculates A1 and A2 
> as 0x100 ((32767+64)/2^7) which is then written as "0" 
> (=completely transparent) if the output is RGBA.

something like
*255 + 16384 >> 15

should work better

that said, the cliping will probably be needed too for some filters
but the >> 7 is wrong if 32767 is the "white" point

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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