rtc: Fixes/adjustments to dynamic resize

For resize_mode = 3 (dynamic): add flag to
disallow 3/4 down/up switch, and increase
the time window for switching down/up.
Keep this flag (one_half_only) on as default
for now.

This reduces resolution toggling observed
in some tests.

Also relax the conditions for entering
the resize logic: allow it for screen content
mode and for aq_mode enabled.

Change-Id: If0851953e0f432b206a917557cfb0176cee4e095

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index b1c68d8..424de3e 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -3595,6 +3595,7 @@
   const int min_width = (160 * 4) / 3;
   const int min_height = (90 * 4) / 3;
   int down_size_on = 1;
+  int one_half_only = 1;
   // Don't resize on key frame; reset the counters on key frame.
   if (cm->current_frame.frame_type == KEY_FRAME) {
     rc->resize_avg_qp = 0;
@@ -3606,14 +3607,11 @@
   if ((cm->width * cm->height) < min_width * min_height) down_size_on = 0;
 
   // Resize based on average buffer underflow and QP over some window.
-  // Ignore samples close to key frame or scene change, since QP is usually high
+  // Ignore samples close to key frame and scene change since QP is usually high
   // after key and scene change.
   // Need to incorpoate content/motion from scene detection analysis.
-  if (cpi->rc.frames_since_key > cpi->framerate &&
-      (cpi->oxcf.tune_cfg.content != AOM_CONTENT_SCREEN ||
-       cpi->oxcf.q_cfg.aq_mode != CYCLIC_REFRESH_AQ ||
-       cpi->cyclic_refresh->counter_encode_maxq_scene_change > 4)) {
-    const int window = AOMMIN(30, (int)(2 * cpi->framerate));
+  if (rc->frames_since_key > cpi->framerate && !rc->high_source_sad) {
+    const int window = AOMMAX(60, (int)(3 * cpi->framerate));
     rc->resize_avg_qp += p_rc->last_q[INTER_FRAME];
     if (cpi->ppi->p_rc.buffer_level <
         (int)(30 * p_rc->optimal_buffer_level / 100))
@@ -3633,13 +3631,14 @@
           resize_action = DOWN_ONEHALF;
           rc->resize_state = ONE_HALF;
         } else if (rc->resize_state == ORIG) {
-          resize_action = DOWN_THREEFOUR;
-          rc->resize_state = THREE_QUARTER;
+          resize_action = one_half_only ? DOWN_ONEHALF : DOWN_THREEFOUR;
+          rc->resize_state = one_half_only ? ONE_HALF : THREE_QUARTER;
         }
       } else if (rc->resize_state != ORIG &&
                  avg_qp < avg_qp_thr1 * cpi->rc.worst_quality / 100) {
         if (rc->resize_state == THREE_QUARTER ||
-            avg_qp < avg_qp_thr2 * cpi->rc.worst_quality / 100) {
+            avg_qp < avg_qp_thr2 * cpi->rc.worst_quality / 100 ||
+            one_half_only) {
           resize_action = UP_ORIG;
           rc->resize_state = ORIG;
         } else if (rc->resize_state == ONE_HALF) {

test/resize_test.cc

diff --git a/test/resize_test.cc b/test/resize_test.cc
index ba90fbb..901bc12 100644
--- a/test/resize_test.cc
+++ b/test/resize_test.cc
@@ -983,7 +983,7 @@
   cfg_.g_w = 352;
   cfg_.g_h = 288;
   change_bitrate_ = true;
-  frame_change_bitrate_ = 120;
+  frame_change_bitrate_ = 200;
   set_scale_mode_ = false;
   set_scale_mode2_ = false;
   set_scale_mode3_ = false;
@@ -994,7 +994,7 @@
   // Disable dropped frames.
   cfg_.rc_dropframe_thresh = 0;
   // Starting bitrate low.
-  cfg_.rc_target_bitrate = 100;
+  cfg_.rc_target_bitrate = 30;
   cfg_.rc_resize_mode = RESIZE_DYNAMIC;
   cfg_.g_forced_max_frame_width = 1280;
   cfg_.g_forced_max_frame_height = 1280;