[FFmpeg-devel] PixFmtInfo cleanup

[Michael Niedermayer]

On Sat, Mar 14, 2009 at 01:30:24AM +0100, Stefano Sabatini wrote:
> On date Thursday 2009-03-05 00:51:47 +0100, Michael Niedermayer encoded:
> [...]
> 
> After another look:
> 
> * currently pixdesc.[hc] contains things like:
>   PIX_FMT_RGB656_LE
> 
>   I think you meant:
>   PIX_FMT_RGB656LE
> 
>   (without the underscore) instead, as it is more consistent with the
>   others PIX_FMT_* and other stuff in libav*.

yes the "_" was a unintentional typo


> 
> 
> * Either the PIX_FMT_RGB565_LE description:
> 
>     [PIX_FMT_RGB565_LE] = {
>         .nb_channels  = 3,
>         .log2_chroma_w= 0,
>         .log2_chroma_h= 0,
>         .comp = {
> 
> //               shift
> //                 v
>             {0,1,1,0,4},
>             {0,1,1,5,5},
>             {0,1,2,3,4},
>         },
> 
> is wrong, either the definition of shift:
> uint16_t shift        :3;            ///< number of lsb that must be shifted away to get the value
> 
> in this case it should be the number of *most* significant bits to
> shift away.

its possible i xchanged 0 and 3 by mistake


> 
> Also what's the interpretation of offset_plus1 if the value is 0?
> Only example is
> 
>      [PIX_FMT_RGB565_BE] = {
>         .nb_channels  = 3,
>         .log2_chroma_w= 0,
>         .log2_chroma_h= 0,
>         .comp = {
>             {0,1,1, 0,4},
>             {0,1,1, 5,5},
>             {0,1,0, 3,4},
> //               ^
> //            offset_plus1
>         },
>         .flags = PIX_FMT_BE,
>     },
> 
> when I'd rather expect the same values of the corresponding LE case.

LE is stores like:
gggbbbbb rrrrrggg 
byte0    byte1

BE is stored like:
rrrrrggg gggbbbbb 
byte0    byte1


for LE 
blue is offset=0, green is 0, red is 1

for BE 
blue is offset=0, green is 0, red is -1
just try to do the 16bit LE & BE reads you will see this is correct

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

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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