[FFmpeg-devel] [PATCH] Use av_clip_uint8 in swscale.

[Måns Rullgård]

Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:

> On Sat, Aug 15, 2009 at 12:27:49PM -0300, Ramiro Polla wrote:
>> diff --git a/swscale.c b/swscale.c
>> index c513066..340acfc 100644
>> --- a/swscale.c
>> +++ b/swscale.c
>> @@ -688,21 +688,12 @@ static inline void yuv2nv12XinC(const int16_t *lumFilter, const int16_t **lumSrc
>>  
>>  #define YSCALE_YUV_2_PACKEDX_C(type,alpha) \
>>          YSCALE_YUV_2_PACKEDX_NOCLIP_C(type,alpha)\
>> -        if ((Y1|Y2|U|V)&256)\
>> -        {\
>> -            if (Y1>255)   Y1=255; \
>> -            else if (Y1<0)Y1=0;   \
>> -            if (Y2>255)   Y2=255; \
>> -            else if (Y2<0)Y2=0;   \
>> -            if (U>255)    U=255;  \
>> -            else if (U<0) U=0;    \
>> -            if (V>255)    V=255;  \
>> -            else if (V<0) V=0;    \
>> -        }\
>> -        if (alpha && ((A1|A2)&256)){\
>> -            A1=av_clip_uint8(A1);\
>> -            A2=av_clip_uint8(A2);\
>> -        }
>> +        Y1 = av_clip_uint8(Y1); \
>> +        Y2 = av_clip_uint8(Y2); \
>> +        U  = av_clip_uint8(U ); \
>> +        V  = av_clip_uint8(V ); \
>> +        A1 = av_clip_uint8(A1); \
>> +        A2 = av_clip_uint8(A2); \
>
> This
>
>> -            if ((u|v)&256){
>> -                if (u<0)        u=0;
>> -                else if (u>255) u=255;
>> -                if (v<0)        v=0;
>> -                else if (v>255) v=255;
>> -            }
>> -
>> -            uDest[i]= u;
>> -            vDest[i]= v;
>> +            uDest[i]= av_clip_uint8((chrSrc[i       ]+64)>>7);
>> +            vDest[i]= av_clip_uint8((chrSrc[i + VOFW]+64)>>7);
>
> And this need to be benchmarked (well, or at least have a look at the
> generated code.
> If clipping is very, very rare the original code might be faster.

Depends on hardware.  On processors with fast clipping instructions,
always clipping is likely to be faster.

-- 
M?ns Rullg?rd
mans at mansr.com