shithub: libvpx

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Merge "Improved slide show coding"

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

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

@@ -2441,8 +2441,9 @@

       loop_decay_rate = get_prediction_decay_rate(cpi, &next_frame);

       // Monitor for static sections.

-      zero_motion_accumulator = VPXMIN(

-          zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));

+      if ((rc->frames_since_key + i - 1) > 1) {

+        zero_motion_accumulator *= get_zero_motion_factor(cpi, &next_frame);

+      }

       // Break clause to detect very still sections after motion. For example,

       // a static image after a fade or other transition.

@@ -2464,8 +2465,17 @@

     // Break out conditions.

     // Break at maximum of active_max_gf_interval unless almost totally static.

-    if (((twopass->kf_zeromotion_pct < STATIC_KF_GROUP_THRESH) &&

-         (i >= active_max_gf_interval) && (zero_motion_accumulator < 0.995)) ||

+    //

+    // Note that the addition of a test of rc->source_alt_ref_active is

+    // deliberate. The effect of this is that after a normal altref group even

+    // if the material is static there will be one normal length GF group

+    // before allowing longer GF groups. The reason for this is that in cases

+    // such as slide shows where slides are separated by a complex transition

+    // such as a fade, the arf group spanning the transition may not be coded

+    // at a very high quality and hence this frame (with its overlay) is a

+    // poor golden frame to use for an extended group.

+    if (((i >= active_max_gf_interval) &&

+         ((zero_motion_accumulator < 0.995) || (rc->source_alt_ref_active))) ||

         (

             // Don't break out with a very short interval.

             (i >= active_min_gf_interval) &&

@@ -2485,7 +2495,7 @@

   rc->constrained_gf_group = (i >= rc->frames_to_key) ? 1 : 0;

   // Should we use the alternate reference frame.

-  if ((twopass->kf_zeromotion_pct < STATIC_KF_GROUP_THRESH) && allow_alt_ref &&

+  if ((zero_motion_accumulator < 0.995) && allow_alt_ref &&

       (i < cpi->oxcf.lag_in_frames) && (i >= rc->min_gf_interval)) {

     const int forward_frames = (rc->frames_to_key - i >= i - 1)

                                    ? i - 1

@@ -2513,11 +2523,11 @@

   rc->gfu_boost = VPXMIN((int)rc->gfu_boost, i * 200);

 #endif

-  // Set the interval until the next gf.

   rc->baseline_gf_interval =

-      (twopass->kf_zeromotion_pct < STATIC_KF_GROUP_THRESH)

-          ? (i - (is_key_frame || rc->source_alt_ref_pending))

-          : i;

+      ((twopass->kf_zeromotion_pct >= STATIC_KF_GROUP_THRESH) &&

+       (i >= rc->frames_to_key))

+          ? i

+          : (i - (is_key_frame || rc->source_alt_ref_pending));

   rc->frames_till_gf_update_due = rc->baseline_gf_interval;

@@ -2764,6 +2774,7 @@

   vp9_zero(next_frame);

   cpi->common.frame_type = KEY_FRAME;

+  rc->frames_since_key = 0;

   // Reset the GF group data structures.

   vp9_zero(*gf_group);

@@ -2908,7 +2919,10 @@

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

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

-    if (i <= KF_BOOST_SCAN_MAX_FRAMES) {

+    // 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)) {

       double frame_boost;

       double zm_factor;