[FFmpeg-cvslog] r27730 - in trunk/libswscale: swscale.c swscale_internal.h

[Vitor Sessak]

Michael Niedermayer wrote:
> On Mon, Oct 20, 2008 at 06:27:36PM +0200, Vitor Sessak wrote:
>> Michael Niedermayer wrote:
>>> On Sun, Oct 19, 2008 at 08:25:41PM +0200, Vitor Sessak wrote:
>>>> Michael Niedermayer wrote:
>>>>> On Sat, Oct 18, 2008 at 11:55:58PM +0200, Vitor Sessak wrote:
>>>>>> vitor wrote:
>>>>>>> Author: vitor
>>>>>>> Date: Wed Oct  8 19:46:22 2008
>>>>>>> New Revision: 27730
>>>>>>> Log:
>>>>>>> Add a new unscaled PAL8 -> RGB converter.
>>>>>> 1000l for me for this patch. I tested it, but without noticing that 
>>>>>> typing "make" do _not_ rebuild swscale-example. Actually it made a 
>>>>>> small regression in {PAL,RGB8,BGR8,RGB4,BGR4}->{RGB32, BGR32}.
>>>>>>
>>>>>> Three possibilities:
>>>>>>
>>>>>> 1- Revert it
>>>>>> 2- sws_fix10l.diff: fix the actual bug (in rgb2rgb.c)
>>>>>> 3- sws_hack.diff: just fix my breakage
>>>>> i do not think 2 or 3 fix the code
>>>>> the palette is in RGB32 format IIRC so one side of the #ifdef has to be
>>>>> wrong. Also the rgb24 would need ifdefs which it does not have, or the
>>>>> palette would have to be converted into a differnt byte order or the
>>>>> switch case would need to be changed a little
>>>> AFAIK, before the palette was either in BGR32 or RGB32 depending on 
>>>> alignment. Now I've made everything alignment independent. Also, if I 
>>>> understand correctly the code, I think that swscaler uses a slightly 
>>>> unusual definition of RGB/BGR.
>>> the swscaler uses the same definition as lav* uses, and its very similar
>>> to mplayers except some rgb <-> bgr flips
>>> These definitions have also been choosen that way for efficiency and
>>> simplicity.
>>> anyway, this patch doesnt look correct either
>>> i suggest you read the definition of the formats in avutils.h
>> Documented header files are a bliss =)
>>
>> Hopefully correct version attached.
>>
>> -Vitor
> 
> [...]
>>  void palette8tobgr32(const uint8_t *src, uint8_t *dst, long num_pixels, const uint8_t *palette)
>>  {
>>      long i;
>> -    for (i=0; i<num_pixels; i++)
>> -    {
>> -        #ifdef WORDS_BIGENDIAN
>> -            dst[3]= palette[src[i]*4+0];
>> -            dst[2]= palette[src[i]*4+1];
>> -            dst[1]= palette[src[i]*4+2];
>> -        #else
>> -            //FIXME slow?
>> -            dst[0]= palette[src[i]*4+0];
>> -            dst[1]= palette[src[i]*4+1];
>> -            dst[2]= palette[src[i]*4+2];
>> -            //dst[3]= 0; /* do we need this cleansing? */
>> -        #endif
>>  
>> -        dst+= 4;
>> -    }
>> +    for (i=0; i<num_pixels; i++)
>> +        ((uint32_t *) dst)[i] =
>> +            bswap_32(((const uint32_t *) palette)[src[i]]) >> 8;
>>  }
> 
> i think it would be faster to bswap 256 entries in palette than
> width*height, besides this would allow the same code to be used for
> rgb & bgr

Yes, but it would have to be done in swscale(). Isn't having both 
pal_rgb[] and pal_bgr[] in the context a bit of an overkill? Also 
palette8tobgr32() is a public function, so I think it should either be 
fixed or removed...

-Vitor