[x265] [PATCH 4 of 5] added C primitives to compute SSIM

[Aarthi Thirumalai]

# HG changeset patch
# User Aarthi Thirumalai
# Date 1380343703 -19800
#      Sat Sep 28 10:18:23 2013 +0530
# Node ID a8b00de495520f00a4648dac5d111e40b5570ca3
# Parent  1d27b6c649ab4580b1fef5ff8b65bb3e1ffa83b6
added C primitives to compute SSIM

diff -r 1d27b6c649ab -r a8b00de49552 source/common/pixel.cpp
--- a/source/common/pixel.cpp	Sat Sep 28 10:12:44 2013 +0530
+++ b/source/common/pixel.cpp	Sat Sep 28 10:18:23 2013 +0530
@@ -636,7 +636,76 @@
     }
 }
 
-}  // end anonymous namespace
+
+/****************************************************************************
+ * structural similarity metric
+ ****************************************************************************/
+void ssim4x4x2Core( const pixel *pix1, intptr_t stride1,
+                             const pixel *pix2, intptr_t stride2,
+                             int sums[2][4] )
+{
+    for( int z = 0; z < 2; z++ )
+    {
+        uint32_t s1 = 0, s2 = 0, ss = 0, s12 = 0;
+        for( int y = 0; y < 4; y++ )
+            for( int x = 0; x < 4; x++ )
+            {
+                int a = pix1[x + y * stride1];
+                int b = pix2[x + y * stride2];
+                s1  += a;
+                s2  += b;
+                ss  += a*a;
+                ss  += b*b;
+                s12 += a*b;
+            }
+        sums[z][0] = s1;
+        sums[z][1] = s2;
+        sums[z][2] = ss;
+        sums[z][3] = s12;
+        pix1 += 4;
+        pix2 += 4;
+    }
+}
+
+ float ssim_end1( int s1, int s2, int ss, int s12 )
+{
+/* Maximum value for 10-bit is: ss*64 = (2^10-1)^2*16*4*64 = 4286582784, which will overflow in some cases.
+ * s1*s1, s2*s2, and s1*s2 also obtain this value for edge cases: ((2^10-1)*16*4)^2 = 4286582784.
+ * Maximum value for 9-bit is: ss*64 = (2^9-1)^2*16*4*64 = 1069551616, which will not overflow. */
+    static const uint16_t pixelMax = (1 << X265_DEPTH)-1;
+#if BIT_DEPTH > 9
+#define type float
+    static const float ssim_c1 = .01 * .01 * pixelMax * pixelMax * 64;
+    static const float ssim_c2 = .03 * .03 * pixelMax * pixelMax * 64 * 63;
+#else
+#define type int
+    static const int ssim_c1 = (int)(.01 *.01 * pixelMax * pixelMax * 64 + .5);
+    static const int ssim_c2 = (int)(.03*.03 * pixelMax * pixelMax * 64 * 63 + .5);
+#endif
+    type fs1 = s1;
+    type fs2 = s2;
+    type fss = ss;
+    type fs12 = s12;
+    type vars = fss * 64 - fs1 * fs1 - fs2 * fs2;
+    type covar = fs12 * 64 - fs1 * fs2;
+    return (float)(2 * fs1 * fs2 + ssim_c1) * (float)(2 * covar + ssim_c2)
+         / ((float)(fs1 * fs1 + fs2 * fs2 + ssim_c1) * (float)(vars + ssim_c2));
+#undef type
+}
+
+ float ssimEnd4( int sum0[5][4], int sum1[5][4], int width )
+{
+    float ssim = 0.0;
+    for( int i = 0; i < width; i++ )
+        ssim += ssim_end1( sum0[i][0] + sum0[i+1][0] + sum1[i][0] + sum1[i+1][0],
+                           sum0[i][1] + sum0[i+1][1] + sum1[i][1] + sum1[i+1][1],
+                           sum0[i][2] + sum0[i+1][2] + sum1[i][2] + sum1[i+1][2],
+                           sum0[i][3] + sum0[i+1][3] + sum1[i][3] + sum1[i+1][3] );
+    return ssim;
+}
+
+ 
+}  // end anonymous namespace 
 
 namespace x265 {
 // x265 private namespace
@@ -851,5 +920,7 @@
     p.scale1D_128to64 = scale1D_128to64;
     p.scale2D_64to32 = scale2D_64to32;
     p.frame_init_lowres_core = frame_init_lowres_core;
+    p.ssim4x4x2Core = ssim4x4x2Core;
+    p.ssimEnd4 = ssimEnd4;
 }
 }
diff -r 1d27b6c649ab -r a8b00de49552 source/common/primitives.h
--- a/source/common/primitives.h	Sat Sep 28 10:12:44 2013 +0530
+++ b/source/common/primitives.h	Sat Sep 28 10:18:23 2013 +0530
@@ -233,6 +233,9 @@
 typedef void (*scale_t)(pixel *dst, pixel *src, intptr_t stride);
 typedef void (*downscale_t)(pixel *src0, pixel *dstf, pixel *dsth, pixel *dstv, pixel *dstc,
                             intptr_t src_stride, intptr_t dst_stride, int width, int height);
+typedef void (*ssim_4x4x2_core)( const pixel *pix1, intptr_t stride1, const pixel *pix2, intptr_t stride2, int sums[2][4] );
+typedef float (*ssim_end4)( int sum0[5][4], int sum1[5][4], int width );
+
 
 /* Define a structure containing function pointers to optimized encoder
  * primitives.  Each pointer can reference either an assembly routine,
@@ -297,6 +300,10 @@
     scale_t         scale1D_128to64;
     scale_t         scale2D_64to32;
     downscale_t     frame_init_lowres_core;
+
+    ssim_4x4x2_core ssim4x4x2Core;
+    ssim_end4       ssimEnd4;
+
 };
 
 /* This copy of the table is what gets used by the encoder.