Revision 8a322796 libswscale/internal_bfin.S
libswscale/internal_bfin.S  

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* Copyright (C) 2007 Marc Hoffman <marc.hoffman@analog.com> 
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* April 20, 2007 
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* 
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* Blackfin Video Color Space Converters Operations


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* convert I420 YV12 to RGB in various formats,


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* Blackfin video color space converter operations


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* convert I420 YV12 to RGB in various formats


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* 
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* This file is part of FFmpeg. 
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* 
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/* 
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YUV420 to RGB565 conversion. This routine takes a YUV 420 planar macroblock


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and converts it to RGB565. R:5 bits, G:6 bits, B:5 bits.. packed into shorts


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YUV420 to RGB565 conversion. This routine takes a YUV 420 planar macroblock 

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and converts it to RGB565. R:5 bits, G:6 bits, B:5 bits.. packed into shorts.


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The following calculation is used for the conversion: 
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g = clipz((yoy)*cy + cgv*(v128) + cgu*(u128)) 
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b = clipz((yoy)*cy + cbu*(u128)) 
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y,u,v are pre scaled by a factor of 4 i.e. left shifted to gain precision.


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y,u,v are prescaled by a factor of 4 i.e. leftshifted to gain precision.


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New factorization to eliminate the truncation error which was 
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occuring due to the byteop3p. 

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occurring due to the byteop3p.


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1) use the bytop16m to subtract quad bytes we use this in U8 this


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1) Use the bytop16m to subtract quad bytes we use this in U8 this


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then so the offsets need to be renormalized to 8bits. 
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2) scale operands up by a factor of 4 not 8 because Blackfin


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2) Scale operands up by a factor of 4 not 8 because Blackfin


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multiplies include a shift. 
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3) compute into the accumulators cy*yx0, cy*yx1


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3) Compute into the accumulators cy*yx0, cy*yx1.


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4) compute each of the linear equations


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4) Compute each of the linear equations:


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r = clipz((y  oy) * cy + crv * (v  128)) 
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g = clipz((y  oy) * cy + cgv * (v  128) + cgu * (u  128)) 
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b = clipz((y  oy) * cy + cbu * (u  128)) 
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reuse of the accumulators requires that we actually multiply


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twice once with addition and the second time with a subtaction. 

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Reuse of the accumulators requires that we actually multiply


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twice once with addition and the second time with a subtraction.


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because of this we need to compute the equations in the order R B


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Because of this we need to compute the equations in the order R B


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then G saving the writes for B in the case of 24/32 bit color 
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formats. 
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api: yuv2rgb_kind (uint8_t *Y, uint8_t *U, uint8_t *V, int *out,


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API: yuv2rgb_kind (uint8_t *Y, uint8_t *U, uint8_t *V, int *out,


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int dW, uint32_t *coeffs); 
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A B 
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coeffs is a pointer to oy. 
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the {rgb} masks are only utilized by the 565 packing algorithm. Note the data


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replication is used to simplify the internal algorithms for the dual mac architecture


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of BlackFin. 

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The {rgb} masks are only utilized by the 565 packing algorithm. Note the data


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replication is used to simplify the internal algorithms for the dual Mac


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architecture of BlackFin.


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All routines are exported with _ff_bfin_ as a symbol prefix 

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All routines are exported with _ff_bfin_ as a symbol prefix.


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rough performance gain compared against O3:


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Rough performance gain compared against O3:


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2779809/1484290 187.28% 
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Also available in: Unified diff