[Ffmpeg-devel] PIX_FMT_RGB555 and alpha channel

Michael Niedermayer michaelni
Tue Oct 31 00:13:29 CET 2006


On Tue, Oct 31, 2006 at 08:42:29AM +1100, Steven Johnson wrote:
> Before I start, this post has nothing to do with the FLC Encoder.  I am 
> happy to have it mask pixels and what not.  It doesn't matter to me 
> either way, but I am confused about the pixel formats.
> I just looked into libswscale to see what it does, as I had a bunch of 
> patches for the swscale inside FFMpeg, but Alex informs me that they 
> wont be accepted for a number of reasons, but a big one is that there is 
> a move towards using libswscale by preference, so I was seeing what the 
> work of adding them to libswscale was. (The other issues I believe I can 
> resolve).
> I noticed that for rgb15 formats libswscale always sets the MSBit to 0.  
> Which is not what FFMpeg does for this format.  With the MSBit = 0, 
> FFMpeg would say that the pixel is fully transparent. They would all 
> need to be or'd with 0x8000 to have the same format as FFMpeg RGB555.   
> Is this a bug?  Should they be or'd with 0x8000 to make the format == to 
> FFMpeg's version?

no IMHO imgconvert is buggy, it should never set the "alpha" bit of rgb555

> Also, it would appear that there is no Alpha support in libswscale, is 
> that correct? 

yes, but img* also doesnt have much alpha support at least not much
working ...


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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