[x265] [PATCH 1 of 2] primitives: added C primitives to compute SSIM
Steve Borho
steve at borho.org
Fri Oct 4 21:23:04 CEST 2013
On Fri, Oct 4, 2013 at 6:21 AM, Aarthi Thirumalai <
aarthi at multicorewareinc.com> wrote:
> # HG changeset patch
> # User Aarthi Thirumalai
> # Date 1380885375 -19800
> # Fri Oct 04 16:46:15 2013 +0530
> # Node ID 92641f3d3195b8da2275cfc44b1921d8f81a54bc
> # Parent bf14f75b8cf99806c75cdc1a50b28b6cf265e3bd
> primitives: added C primitives to compute SSIM
>
> diff -r bf14f75b8cf9 -r 92641f3d3195 source/common/pixel.cpp
> --- a/source/common/pixel.cpp Fri Oct 04 01:39:22 2013 -0500
> +++ b/source/common/pixel.cpp Fri Oct 04 16:46:15 2013 +0530
> @@ -653,6 +653,85 @@
> }
> }
>
> +/* structural similarity metric */
> +template<class T1>
> +void ssim_4x4x2_core(const pixel *pix1, intptr_t stride1, const pixel
> *pix2, intptr_t stride2, T1 sums[2][4])
> +{
> + for (int z = 0; z < 2; z++)
> + {
> + T1 s1 = 0, s2 = 0, ss = 0, s12 = 0;
> + for (int y = 0; y < 4; y++)
> + {
> + for (int x = 0; x < 4; x++)
> + {
> + T1 a = pix1[x + y * stride1];
> + T1 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;
> + }
> +}
> +
> +template<class T1>
> +float ssim_end_4(T1 sum0[5][4], T1 sum1[5][4], int width)
> +{
> + float ssim = 0.0;
> +
> + for (int i = 0; i < width; i++)
> + {
> + ssim += ssim_end_1(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;
> +}
> +
> +float ssim_end_1(int s1, int s2, int ss, int s12)
> +{
> + static const uint32_t pixelMax = (1 << X265_DEPTH) - 1;
> +
> + /* 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. */
> +
> +#if X265_DEPTH > 9
> +#define type int64_t
> +#else
> +#define type int32_t
> +#endif
>
We keep cycling on this issue.
With HIGH_BIT_DEPTH=1, X265_DEPTH evaluates to g_bitDepth (a global
variable)
With HIGH_BIT_DEPTH=0, X265_DEPTH evaluates to 8
So with high bit depth builds the bit depth is a runtime option (it could
be 8, 10, or 12). For 8bpp builds the bit depth must be 8.
HIGH_BIT_DEPTH=0 builds will probably always use the uint32 version of this
function. The HIGH_BIT_DEPTH=1 builds will have to choose between uint32
or float at runtime.
> +
> + static const type ssim_c1 = (type)(.01 * .01 * pixelMax * pixelMax *
> 64 + .5);
> + static const type ssim_c2 = (type)(.03 * .03 * pixelMax * pixelMax *
> 64 * 63 + .5);
> + type vars = ss * 64 - s1 * s1 - s2 * s2;
> + type covar = s12 * 64 - s1 * s2;
> + return (float)(2 * s1 * s2 + ssim_c1) * (float)(2 * covar + ssim_c2)
> + / ((float)(s1 * s1 + s2 * s2 + ssim_c1) * (float)(vars +
> ssim_c2));
> +}
> +
> +float ssim_end_1(float s1, float s2, float ss, float s12)
> +{
> + static const float pixelMax = (1 << X265_DEPTH) - 1;
> + static const float ssim_c1 = (float)(.01 * .01 * pixelMax * pixelMax
> * 64);
> + static const float ssim_c2 = (float)(.03 * .03 * pixelMax * pixelMax
> * 64 * 63);
> + float vars = ss * 64 - s1 * s1 - s2 * s2;
> + float covar = s12 * 64 - s1 * s2;
> +
> + return (2 * s1 * s2 + ssim_c1) * (2 * covar + ssim_c2)
> + / ((s1 * s1 + s2 * s2 + ssim_c1) * (vars + ssim_c2));
> +}
> } // end anonymous namespace
>
> namespace x265 {
> @@ -870,5 +949,10 @@
> p.scale1D_128to64 = scale1D_128to64;
> p.scale2D_64to32 = scale2D_64to32;
> p.frame_init_lowres_core = frame_init_lowres_core;
> +
> + p.ssim_4x4x2_core_float = ssim_4x4x2_core<float>;
> + p.ssim_4x4x2_core_int = ssim_4x4x2_core<int>;
> + p.ssim_end4_float = ssim_end_4<float>;
> + p.ssim_end4_int = ssim_end_4<int>;
> }
> }
> diff -r bf14f75b8cf9 -r 92641f3d3195 source/common/primitives.h
> --- a/source/common/primitives.h Fri Oct 04 01:39:22 2013 -0500
> +++ b/source/common/primitives.h Fri Oct 04 16:46:15 2013 +0530
> @@ -235,6 +235,10 @@
> 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_int_t)(const pixel *pix1, intptr_t
> stride1, const pixel *pix2, intptr_t stride2, int sums[2][4]);
> +typedef void (*ssim_4x4x2_core_float_t)(const pixel *pix1, intptr_t
> stride1, const pixel *pix2, intptr_t stride2, float sums[2][4]);
> +typedef float (*ssim_end4_int_t)(int sum0[5][4], int sum1[5][4], int
> width);
> +typedef float (*ssim_end4_float_t)(float sum0[5][4], float sum1[5][4],
> int width);
>
> /* Define a structure containing function pointers to optimized encoder
> * primitives. Each pointer can reference either an assembly routine,
> @@ -301,6 +305,13 @@
> scale_t scale1D_128to64;
> scale_t scale2D_64to32;
> downscale_t frame_init_lowres_core;
> +
> +/* If the pixel depth >15 , use the ssim_float primitives to prevent
> overflow, else
> + * ssim_int primitves should be sufficient. */
> + ssim_4x4x2_core_int_t ssim_4x4x2_core_int;
> + ssim_4x4x2_core_float_t ssim_4x4x2_core_float;
> + ssim_end4_int_t ssim_end4_int;
> + ssim_end4_float_t ssim_end4_float;
> };
>
> /* This copy of the table is what gets used by the encoder.
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
--
Steve Borho
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