Commit initial reference implementation of IDCT.

[fjl] / idct_test.c

diff --git a/idct_test.c b/idct_test.c
new file mode 100644 (file)
index 0000000..7dfac43
--- /dev/null
+++ b/idct_test.c
@@ -0,0 +1,130 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+#include <assert.h>
+#include <time.h>
+#include <sys/time.h>
+
+#include "idct.h"
+
+// Generate random coefficients in the range [-15..15].
+void gen_random_coeffs(int16_t* dst, size_t len)
+{
+       // Standard NR LCG (we avoid rand() to get consistent behavior across platforms).
+       static uint32_t seed = 1234;
+       for (unsigned i = 0; i < len; ++i) {
+               seed = seed * 1664525U + 1013904223U;
+               if (seed >> 31) {
+                       dst[i] = (uint8_t)(seed >> 27) & 0x7;
+               } else {
+                       dst[i] = -((uint8_t)(seed >> 27) & 0x7);
+               }
+       }
+}
+
+// Test that the input is pretty close to the reference for random inputs. 
+// (If the reference funtion is given in, this becomes a simple test of its
+// determinism.)
+void test_random_inputs(idct_func_t* idct)
+{
+       int16_t coeff[DCTSIZE2]; 
+       uint32_t quant[DCTSIZE2];
+       uint8_t output[DCTSIZE2];
+       uint8_t reference[DCTSIZE2];
+               
+       // Unit quantization (ie., no scaling).
+       for (unsigned i = 0; i < DCTSIZE2; ++i) {
+               quant[i] = 1;
+       }
+
+       for (unsigned i = 0; i < 1000; ++i) {   
+               gen_random_coeffs(coeff, DCTSIZE2);
+
+               (*idct)(coeff, quant, output);
+               (idct_reference)(coeff, quant, reference);
+
+               // Find the RMS difference.
+               int diff_squared = 0;
+               for (unsigned i = 0; i < DCTSIZE2; ++i) {
+                       diff_squared += (output[i] - reference[i]) * (output[i] - reference[i]);
+               }
+
+               assert(diff_squared <= 5);
+       }
+}
+
+// Test that a single DC coefficient becomes spread out to all blocks.
+void test_dc_becomes_spread_out(idct_func_t* idct)
+{
+       int16_t coeff[DCTSIZE2] = { 0 }; 
+       uint32_t quant[DCTSIZE2];
+       uint8_t output[DCTSIZE2];
+
+       // Unit quantization (ie., no scaling).
+       for (unsigned i = 0; i < DCTSIZE2; ++i) {
+               quant[i] = 1;
+       }
+
+       for (unsigned i = 0; i < 255*8; ++i) {  
+               uint32_t reference_value = i / 8;
+               coeff[0] = i;
+
+               (*idct)(coeff, quant, output);
+
+               for (unsigned i = 0; i < DCTSIZE2; ++i) {
+                       assert(abs(output[i] - reference_value) <= 1);
+               }
+       }
+}
+
+double timediff(const struct timeval* a, const struct timeval* b)
+{
+       return (double)(b->tv_sec - a->tv_sec) +
+               (double)(b->tv_usec - a->tv_usec) * 1e-6;
+}
+
+void test_performance(idct_func_t* idct)
+{
+       const unsigned num_runs = (idct == idct_reference) ? 5000 : 5000000;
+
+       int16_t coeff[DCTSIZE2]; 
+       uint32_t quant[DCTSIZE2];
+       uint8_t output[DCTSIZE2];
+               
+       gen_random_coeffs(coeff, DCTSIZE2);
+
+       struct timeval start, now;
+       gettimeofday(&start, NULL);
+
+       for (unsigned i = 0; i < num_runs; ++i) {
+               (*idct)(coeff, quant, output);
+       }
+       
+       gettimeofday(&now, NULL);
+
+       double diff = timediff(&start, &now);
+       printf("%u runs in %.2f seconds = %.2f DCTs/sec\n",
+               num_runs, diff, num_runs / diff);
+}
+
+void test_all_idct(idct_func_t* idct)
+{
+       printf("  test_dc_becomes_spread_out()\n");
+       test_dc_becomes_spread_out(idct);       
+
+       printf("  test_random_inputs()\n");
+       test_random_inputs(idct);       
+
+       printf("  performance test: ");
+       test_performance(idct);
+}
+
+int main(void)
+{
+       printf("idct_reference:\n");
+       test_all_idct(idct_reference);
+
+       printf("All tests pass.\n");
+       return 0;
+}