git.sesse.net Git - fjl/blob - idct_reference.c

   1 #include <math.h>
   2 #include <string.h>
   3 #include <stdlib.h>
   4
   5 #include "idct_reference.h"
   6
   7 void* idct_reference_alloc(const uint32_t* quant_table)
   8 {
   9         uint32_t* qt_copy = (uint32_t*)malloc(DCTSIZE2 * sizeof(uint32_t));
  10         // FIXME: check for NULL return
  11
  12         memcpy(qt_copy, quant_table, DCTSIZE2 * sizeof(uint32_t));
  13
  14         return qt_copy;
  15 }
  16
  17 void idct_reference_free(void* userdata)
  18 {
  19         free(userdata);
  20 }
  21
  22 void idct_reference(const int16_t* input, const void* userdata, uint8_t* output)
  23 {
  24         const uint32_t* quant_table = (const uint32_t*)userdata;
  25         double temp[DCTSIZE2];
  26
  27         for (unsigned y = 0; y < 8; ++y) {
  28                 for (unsigned x = 0; x < 8; ++x) {
  29                         double acc = 0.0;
  30                         for (unsigned u = 0; u < 8; ++u) {
  31                                 for (unsigned v = 0; v < 8; ++v) {
  32                                         double c_u = (u == 0) ? 1/sqrt(2.0) : 1.0;
  33                                         double c_v = (v == 0) ? 1/sqrt(2.0) : 1.0;
  34                                         acc += c_u * c_v
  35                                                 * input[u * DCTSIZE + v] * quant_table[u * DCTSIZE + v]
  36                                                 * cos((2 * x + 1) * v * M_PI / 16.0)
  37                                                 * cos((2 * y + 1) * u * M_PI / 16.0);
  38                                 }
  39                         }
  40                         temp[y * DCTSIZE + x] = 0.25 * acc;
  41                 }
  42         }
  43
  44         for (unsigned y = 0; y < 8; ++y) {
  45                 for (unsigned x = 0; x < 8; ++x) {
  46                         double val = temp[y * DCTSIZE + x] + 128.0;
  47                         if (val < 0.0) {
  48                                 output[y * DCTSIZE + x] = 0;
  49                         } else if (val >= 255.0) {
  50                                 output[y * DCTSIZE + x] = 255;
  51                         } else {
  52                                 output[y * DCTSIZE + x] = (uint8_t)(val + 0.5);
  53                         }
  54                 }
  55         }
  56 }