Define a macro to replace hardcoded values

The definition is for the number of frames to check to determine the
recent decay rate, further to determine the next key frame in the
first pass of the encoder.

Change-Id: Ic696d6eb518a86fa296842273cf8767ef0b0e27a

vp10/encoder/firstpass.c

diff --git a/vp10/encoder/firstpass.c b/vp10/encoder/firstpass.c
index 80e461b..bc1ce00 100644
--- a/vp10/encoder/firstpass.c
+++ b/vp10/encoder/firstpass.c
@@ -2135,6 +2135,8 @@
   return is_viable_kf;
 }
 
+#define FRAMES_TO_CHECK_DECAY 8
+
 static void find_next_key_frame(VP10_COMP *cpi, FIRSTPASS_STATS *this_frame) {
   int i, j;
   RATE_CONTROL *const rc = &cpi->rc;
@@ -2153,7 +2155,7 @@
   double boost_score = 0.0;
   double kf_mod_err = 0.0;
   double kf_group_err = 0.0;
-  double recent_loop_decay[8] = {1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0};
+  double recent_loop_decay[FRAMES_TO_CHECK_DECAY];
 
   vp10_zero(next_frame);
 
@@ -2180,6 +2182,10 @@
 
   kf_mod_err = calculate_modified_err(cpi, twopass, oxcf, this_frame);
 
+  // Initialize the decay rates for the recent frames to check
+  for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
+    recent_loop_decay[j] = 1.0;
+
   // Find the next keyframe.
   i = 0;
   while (twopass->stats_in < twopass->stats_in_end &&
@@ -2206,9 +2212,9 @@
       // We want to know something about the recent past... rather than
       // as used elsewhere where we are concerned with decay in prediction
       // quality since the last GF or KF.
-      recent_loop_decay[i % 8] = loop_decay_rate;
+      recent_loop_decay[i % FRAMES_TO_CHECK_DECAY] = loop_decay_rate;
       decay_accumulator = 1.0;
-      for (j = 0; j < 8; ++j)
+      for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
         decay_accumulator *= recent_loop_decay[j];
 
       // Special check for transition or high motion followed by a

vp9/encoder/vp9_firstpass.c

diff --git a/vp9/encoder/vp9_firstpass.c b/vp9/encoder/vp9_firstpass.c
index 71843ee..9d3b154 100644
--- a/vp9/encoder/vp9_firstpass.c
+++ b/vp9/encoder/vp9_firstpass.c
@@ -2260,6 +2260,8 @@
   return is_viable_kf;
 }
 
+#define FRAMES_TO_CHECK_DECAY 8
+
 static void find_next_key_frame(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
   int i, j;
   RATE_CONTROL *const rc = &cpi->rc;
@@ -2278,7 +2280,7 @@
   double boost_score = 0.0;
   double kf_mod_err = 0.0;
   double kf_group_err = 0.0;
-  double recent_loop_decay[8] = {1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0};
+  double recent_loop_decay[FRAMES_TO_CHECK_DECAY];
 
   vp9_zero(next_frame);
 
@@ -2305,6 +2307,10 @@
 
   kf_mod_err = calculate_modified_err(cpi, twopass, oxcf, this_frame);
 
+  // Initialize the decay rates for the recent frames to check
+  for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
+    recent_loop_decay[j] = 1.0;
+
   // Find the next keyframe.
   i = 0;
   while (twopass->stats_in < twopass->stats_in_end &&
@@ -2331,9 +2337,9 @@
       // We want to know something about the recent past... rather than
       // as used elsewhere where we are concerned with decay in prediction
       // quality since the last GF or KF.
-      recent_loop_decay[i % 8] = loop_decay_rate;
+      recent_loop_decay[i % FRAMES_TO_CHECK_DECAY] = loop_decay_rate;
       decay_accumulator = 1.0;
-      for (j = 0; j < 8; ++j)
+      for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
         decay_accumulator *= recent_loop_decay[j];
 
       // Special check for transition or high motion followed by a