KF/GF Pulsing

This change is designed to try and reduce pulsing effects when moving
with a complex transition like a fade, into an easy or static section in
an otherwise difficult clip in CQ mode.

The active CQ level is relaxed down to the user entered level for frames that
are generating less than the passed in minimum bandwidth.

Change-Id: Id6d8b551daad4f489c087bd742bc95418a95f3f0

vp8/encoder/onyx_if.c

diff --git a/vp8/encoder/onyx_if.c b/vp8/encoder/onyx_if.c
index 470a9ac..e0d1d70 100644
--- a/vp8/encoder/onyx_if.c
+++ b/vp8/encoder/onyx_if.c
@@ -2029,7 +2029,7 @@
     cpi->buffered_mode = (cpi->oxcf.optimal_buffer_level > 0) ? TRUE : FALSE;
 
     // Experimental cq target value
-    cpi->cq_target_quality = oxcf->cq_level;
+    cpi->cq_target_quality = cpi->oxcf.cq_level;
 
     cpi->rolling_target_bits          = cpi->av_per_frame_bandwidth;
     cpi->rolling_actual_bits          = cpi->av_per_frame_bandwidth;
@@ -3519,14 +3519,29 @@
     {
         // General over and under shoot tests
         if ( ((cpi->projected_frame_size > high_limit) && (q < maxq)) ||
-             ((cpi->projected_frame_size < low_limit) && (q > minq)) ||
-             ((cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY) &&
-              (q > cpi->cq_target_quality) &&
-              (cpi->projected_frame_size <
-                  ((cpi->this_frame_target * 7) >> 3))) )
+             ((cpi->projected_frame_size < low_limit) && (q > minq)) )
         {
             force_recode = TRUE;
         }
+        // Special Constrained quality tests
+        else if (cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY)
+        {
+            // Undershoot and below auto cq level
+            if ( (q > cpi->cq_target_quality) &&
+                 (cpi->projected_frame_size <
+                     ((cpi->this_frame_target * 7) >> 3)))
+            {
+                force_recode = TRUE;
+            }
+            // Severe undershoot and between auto and user cq level
+            else if ( (q > cpi->oxcf.cq_level) &&
+                      (cpi->projected_frame_size < cpi->min_frame_bandwidth) &&
+                      (cpi->active_best_quality > cpi->oxcf.cq_level))
+            {
+                force_recode = TRUE;
+                cpi->active_best_quality = cpi->oxcf.cq_level;
+            }
+        }
     }
 
     return force_recode;
@@ -3853,7 +3868,13 @@
             if ((cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY) &&
                 (cpi->active_best_quality < cpi->cq_target_quality) )
             {
-                cpi->active_best_quality = cpi->cq_target_quality;
+                // If we are strongly undershooting the target rate in the last
+                // frames then use the user passed in cq value not the auto
+                // cq value.
+                if ( cpi->rolling_actual_bits < cpi->min_frame_bandwidth )
+                    cpi->active_best_quality = cpi->oxcf.cq_level;
+                else
+                    cpi->active_best_quality = cpi->cq_target_quality;
             }
         }
 
@@ -4219,6 +4240,16 @@
 
                     Q = vp8_regulate_q(cpi, cpi->this_frame_target);
 
+                    // Special case reset for qlow for constrained quality.
+                    // This should only trigger where there is very substantial
+                    // undershoot on a frame and the auto cq level is above
+                    // the user passsed in value.
+                    if ( (cpi->oxcf.end_usage == USAGE_CONSTRAINED_QUALITY) &&
+                         (Q < q_low) )
+                    {
+                        q_low = Q;
+                    }
+
                     while (((Q > q_high) || (cpi->zbin_over_quant > zbin_oq_high)) && (Retries < 10))
                     {
                         vp8_update_rate_correction_factors(cpi, 0);