From d7a9a57976213e368e6917fae50575d879076b9c Mon Sep 17 00:00:00 2001 From: "Steinar H. Gunderson" Date: Sat, 16 Sep 2017 15:11:24 +0200 Subject: [PATCH] Add a PSNR measurement tool. --- psnr.cpp | 148 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 148 insertions(+) create mode 100644 psnr.cpp diff --git a/psnr.cpp b/psnr.cpp new file mode 100644 index 0000000..fa303de --- /dev/null +++ b/psnr.cpp @@ -0,0 +1,148 @@ +#include +#include +#include +#include +#include +#include + +#define WIDTH 1280 +#define HEIGHT 720 +#define NUM_SYMS 256 +#define ESCAPE_LIMIT (NUM_SYMS - 1) + +using namespace std; + +unsigned char pix1[WIDTH * HEIGHT], pix2[WIDTH * HEIGHT]; + +void readpix(unsigned char *ptr, const char *filename) +{ + FILE *fp = fopen(filename, "rb"); + if (fp == nullptr) { + perror(filename); + exit(1); + } + + fseek(fp, 0, SEEK_END); + long len = ftell(fp); + assert(len >= WIDTH * HEIGHT); + fseek(fp, len - WIDTH * HEIGHT, SEEK_SET); + + fread(ptr, 1, WIDTH * HEIGHT, fp); + fclose(fp); +} + +/**************************************************************************** + * structural similarity metric + ****************************************************************************/ +static void ssim_4x4x2_core( const uint8_t *pix1, intptr_t stride1, + const uint8_t *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; + } +} + +#define PIXEL_MAX 255 + +static 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. */ +#define type int + static const int ssim_c1 = (int)(.01*.01*PIXEL_MAX*PIXEL_MAX*64 + .5); + static const int ssim_c2 = (int)(.03*.03*PIXEL_MAX*PIXEL_MAX*64*63 + .5); + 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 +} + +static float ssim_end4( 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; +} + +float x264_pixel_ssim_wxh( + uint8_t *pix1, intptr_t stride1, + uint8_t *pix2, intptr_t stride2, + int width, int height, void * buf, int *cnt ) +{ + int z = 0; + float ssim = 0.0; + int (*sum0)[4] = buf; + int (*sum1)[4] = sum0 + (width >> 2) + 3; + width >>= 2; + height >>= 2; + for( int y = 1; y < height; y++ ) + { + for( ; z <= y; z++ ) + { + swap(sum0, sum1); + for( int x = 0; x < width; x+=2 ) + ssim_4x4x2_core( &pix1[4*(x+z*stride1)], stride1, &pix2[4*(x+z*stride2)], stride2, &sum0[x] ); + } + for( int x = 0; x < width-1; x += 4 ) + ssim += ssim_end4( sum0+x, sum1+x, min(4,width-x-1) ); + } + *cnt = (height-1) * (width-1); + return ssim; +} + +int main(int argc, char **argv) +{ + readpix(pix1, argv[1]); + readpix(pix2, argv[2]); + + double sum_sq_err = 0.0; + + for (unsigned y = 0; y < HEIGHT; ++y) { + for (unsigned x = 0; x < WIDTH; ++x) { + int k1 = pix1[y * WIDTH + x]; + int k2 = pix2[y * WIDTH + x]; + sum_sq_err += (k1 - k2) * (k1 - k2); + } + } + double mse = sum_sq_err / double(WIDTH * HEIGHT); + double psnr_db = 20 * log10(255.0 / sqrt(mse)); + + void *scratch = new int[8 * WIDTH]; + int cnt = 0; + float ssim = x264_pixel_ssim_wxh( + pix1 + 2 + WIDTH*2, WIDTH, + pix2 + 2 + WIDTH*2, WIDTH, + WIDTH - 2, HEIGHT - 2, scratch, &cnt); + ssim /= cnt; + + printf("%.2f %.2f\n", psnr_db, -10.0 * log10(1 - ssim)); +} -- 2.39.2