shithub: libvpx

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Use qsort to find median value

The list is short enough to use qsort.

Change-Id: I5bb1f2c43eec508bafaf4d1ad7c8a92441f066ce

--- a/vp9/encoder/vp9_encoder.c

+++ b/vp9/encoder/vp9_encoder.c

@@ -8,9 +8,10 @@

  *  be found in the AUTHORS file in the root of the source tree.

  */

+#include <limits.h>

 #include <math.h>

 #include <stdio.h>

-#include <limits.h>

+#include <stdlib.h>

 #include "./vp9_rtcd.h"

 #include "./vpx_config.h"

@@ -4718,6 +4719,14 @@

 }

 // Process the wiener variance in 16x16 block basis.

+static int qsort_comp(const void *elem1, const void *elem2) {

+  int a = *((const int *)elem1);

+  int b = *((const int *)elem2);

+  if (a > b) return 1;

+  if (a < b) return -1;

+  return 0;

+}

+

 static void set_mb_wiener_variance(VP9_COMP *cpi) {

   VP9_COMMON *cm = &cpi->common;

   uint8_t *buffer = cpi->Source->y_buffer;

@@ -4762,7 +4771,7 @@

   for (mb_row = 0; mb_row < cm->mb_rows; ++mb_row) {

     for (mb_col = 0; mb_col < cm->mb_cols; ++mb_col) {

-      int idx, hist_count = 0;

+      int idx;

       int16_t median_val = 0;

       uint8_t *mb_buffer =

           buffer + mb_row * block_size * buf_stride + mb_col * block_size;

@@ -4785,18 +4794,13 @@

       wht_fwd_txfm(src_diff, block_size, coeff, tx_size);

 #endif  // CONFIG_VP9_HIGHBITDEPTH

-      for (idx = 0; idx < UINT16_MAX; ++idx) cpi->stack_rank_buffer[idx] = 0;

+      coeff[0] = 0;

+      for (idx = 1; idx < coeff_count; ++idx) coeff[idx] = abs(coeff[idx]);

-      for (idx = 1; idx < coeff_count; ++idx)

-        ++cpi->stack_rank_buffer[abs(coeff[idx])];

+      qsort(coeff, coeff_count, sizeof(*coeff), qsort_comp);

-      for (idx = 0; idx < UINT16_MAX; ++idx) {

-        hist_count += cpi->stack_rank_buffer[idx];

-        if (hist_count >= coeff_count / 2) break;

-      }

-

       // Noise level estimation

-      median_val = idx;

+      median_val = coeff[coeff_count / 2];

       // Wiener filter

       for (idx = 1; idx < coeff_count; ++idx) {