shithub: libvpx

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Refine interval for key frame boost calculation

In the calculation of boost for key frames, increase number
of frames to be scanned based on the content nature.

Change-Id: Ia4533966a00055d0bec712e073d82d4bd1dc715a

--- a/vp9/encoder/vp9_firstpass.c

+++ b/vp9/encoder/vp9_firstpass.c

@@ -2887,7 +2887,9 @@

 #define FRAMES_TO_CHECK_DECAY 8

 #define MIN_KF_TOT_BOOST 300

-#define KF_BOOST_SCAN_MAX_FRAMES 32

+#define DEFAULT_SCAN_FRAMES_FOR_KF_BOOST 32

+#define MAX_SCAN_FRAMES_FOR_KF_BOOST 48

+#define MIN_SCAN_FRAMES_FOR_KF_BOOST 32

 #define KF_ABS_ZOOM_THRESH 6.0

 #ifdef AGGRESSIVE_VBR

@@ -2911,6 +2913,12 @@

   int kf_bits = 0;

   double decay_accumulator = 1.0;

   double zero_motion_accumulator = 1.0;

+  double zero_motion_sum = 0.0;

+  double zero_motion_avg;

+  double motion_compensable_sum = 0.0;

+  double motion_compensable_avg;

+  int num_frames = 0;

+  int kf_boost_scan_frames = DEFAULT_SCAN_FRAMES_FOR_KF_BOOST;

   double boost_score = 0.0;

   double kf_mod_err = 0.0;

   double kf_raw_err = 0.0;

@@ -3063,6 +3071,27 @@

   // how many bits to spend on it.

   boost_score = 0.0;

+  for (i = 0; i < VPXMIN(MAX_SCAN_FRAMES_FOR_KF_BOOST, (rc->frames_to_key - 1));

+       ++i) {

+    if (EOF == input_stats(twopass, &next_frame)) break;

+

+    zero_motion_sum += next_frame.pcnt_inter - next_frame.pcnt_motion;

+    motion_compensable_sum +=

+        1 - (double)next_frame.coded_error / next_frame.intra_error;

+    num_frames++;

+  }

+

+  if (num_frames >= MIN_SCAN_FRAMES_FOR_KF_BOOST) {

+    zero_motion_avg = zero_motion_sum / num_frames;

+    motion_compensable_avg = motion_compensable_sum / num_frames;

+    kf_boost_scan_frames = (int)(VPXMAX(64 * zero_motion_avg - 16,

+                                        160 * motion_compensable_avg - 112));

+    kf_boost_scan_frames =

+        VPXMAX(VPXMIN(kf_boost_scan_frames, MAX_SCAN_FRAMES_FOR_KF_BOOST),

+               MIN_SCAN_FRAMES_FOR_KF_BOOST);

+  }

+  reset_fpf_position(twopass, start_position);

+

   for (i = 0; i < (rc->frames_to_key - 1); ++i) {

     if (EOF == input_stats(twopass, &next_frame)) break;

@@ -3069,7 +3098,7 @@

     // The zero motion test here insures that if we mark a kf group as static

     // it is static throughout not just the first KF_BOOST_SCAN_MAX_FRAMES.

     // It also allows for a larger boost on long static groups.

-    if ((i <= KF_BOOST_SCAN_MAX_FRAMES) || (zero_motion_accumulator >= 0.99)) {

+    if ((i <= kf_boost_scan_frames) || (zero_motion_accumulator >= 0.99)) {

       double frame_boost;

       double zm_factor;