Add dynamic resize logic for 1 pass CBR.

Decision to scale down/up is based on buffer state and average QP
over previous time window. Limit the total amount of down-scaling
to be at most one scale down for now.

Reset certain quantities after resize (buffer level, cyclic refresh,
rate correction factor).

Feature is enable via the setting rc_resize_allowed = 1.

Change-Id: I9b1a53024e1e1e953fb8a1e1f75d21d160280dc7

examples/vpx_temporal_svc_encoder.c

@@ -608,7 +608,6 @@ int main(int argc, char **argv) {
   // Real time parameters.
   cfg.rc_dropframe_thresh = strtol(argv[9], NULL, 0);
   cfg.rc_end_usage = VPX_CBR;
-  cfg.rc_resize_allowed = 0;
   cfg.rc_min_quantizer = 2;
   cfg.rc_max_quantizer = 56;
   if (strncmp(encoder->name, "vp9", 3) == 0)
@@ -619,6 +618,9 @@ int main(int argc, char **argv) {
   cfg.rc_buf_optimal_sz = 600;
   cfg.rc_buf_sz = 1000;
 
+  // Disable dynamic resizing by default.
+  cfg.rc_resize_allowed = 0;
+
   // Use 1 thread as default.
   cfg.g_threads = 1;
 

vp9/encoder/vp9_aq_cyclicrefresh.c

@@ -529,3 +529,10 @@ void vp9_cyclic_refresh_setup(VP9_COMP *const cpi) {
 int vp9_cyclic_refresh_get_rdmult(const CYCLIC_REFRESH *cr) {
   return cr->rdmult;
 }
+
+void vp9_cyclic_refresh_reset_resize(VP9_COMP *const cpi) {
+  const VP9_COMMON *const cm = &cpi->common;
+  CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;
+  memset(cr->map, 0, cm->mi_rows * cm->mi_cols);
+  cr->sb_index = 0;
+}

vp9/encoder/vp9_aq_cyclicrefresh.h

@@ -75,6 +75,8 @@ void vp9_cyclic_refresh_setup(struct VP9_COMP *const cpi);
 
 int vp9_cyclic_refresh_get_rdmult(const CYCLIC_REFRESH *cr);
 
+void vp9_cyclic_refresh_reset_resize(struct VP9_COMP *const cpi);
+
 static INLINE int cyclic_refresh_segment_id_boosted(int segment_id) {
   return segment_id == CR_SEGMENT_ID_BOOST1 ||
          segment_id == CR_SEGMENT_ID_BOOST2;

vp9/encoder/vp9_encoder.c

@@ -1596,6 +1596,9 @@ VP9_COMP *vp9_create_compressor(VP9EncoderConfig *oxcf,
                   sizeof(*cm->frame_contexts)));
 
   cpi->use_svc = 0;
+  cpi->resize_state = 0;
+  cpi->resize_avg_qp = 0;
+  cpi->resize_buffer_underflow = 0;
   cpi->common.buffer_pool = pool;
 
   init_config(cpi, oxcf);
@@ -3032,6 +3035,31 @@ static void set_frame_size(VP9_COMP *cpi) {
                          oxcf->scaled_frame_height);
   }
 
+  if (oxcf->pass == 0 &&
+      oxcf->rc_mode == VPX_CBR &&
+      !cpi->use_svc &&
+      oxcf->resize_mode == RESIZE_DYNAMIC) {
+      if (cpi->resize_state == 1) {
+        oxcf->scaled_frame_width =
+            (cm->width * cpi->resize_scale_num) / cpi->resize_scale_den;
+        oxcf->scaled_frame_height =
+            (cm->height * cpi->resize_scale_num) /cpi->resize_scale_den;
+      } else if (cpi->resize_state == -1) {
+        // Go back up to original size.
+        oxcf->scaled_frame_width = oxcf->width;
+        oxcf->scaled_frame_height = oxcf->height;
+      }
+      if (cpi->resize_state != 0) {
+        // There has been a change in frame size.
+        vp9_set_size_literal(cpi,
+                             oxcf->scaled_frame_width,
+                             oxcf->scaled_frame_height);
+
+        // TODO(agrange) Scale cpi->max_mv_magnitude if frame-size has changed.
+        set_mv_search_params(cpi);
+      }
+  }
+
   if ((oxcf->pass == 2) &&
       (!cpi->use_svc ||
           (is_two_pass_svc(cpi) &&

vp9/encoder/vp9_encoder.h

@@ -479,6 +479,12 @@ typedef struct VP9_COMP {
 #endif
 
   int resize_pending;
+  int resize_state;
+  int resize_scale_num;
+  int resize_scale_den;
+  int resize_avg_qp;
+  int resize_buffer_underflow;
+  int resize_count;
 
   // VAR_BASED_PARTITION thresholds
   // 0 - threshold_64x64; 1 - threshold_32x32;

vp9/encoder/vp9_ratectrl.c

@@ -1596,6 +1596,7 @@ void vp9_rc_get_one_pass_cbr_params(VP9_COMP *cpi) {
     target = calc_pframe_target_size_one_pass_cbr(cpi);
 
   vp9_rc_set_frame_target(cpi, target);
+  cpi->resize_state = vp9_resize_one_pass_cbr(cpi);
 }
 
 int vp9_compute_qdelta(const RATE_CONTROL *rc, double qstart, double qtarget,
@@ -1756,3 +1757,92 @@ void vp9_set_target_rate(VP9_COMP *cpi) {
     vbr_rate_correction(cpi, &target_rate);
   vp9_rc_set_frame_target(cpi, target_rate);
 }
+
+// Check if we should resize, based on average QP from past x frames.
+// Only allow for resize at most one scale down for now, scaling factor is 2.
+int vp9_resize_one_pass_cbr(VP9_COMP *cpi) {
+  const VP9_COMMON *const cm = &cpi->common;
+  RATE_CONTROL *const rc = &cpi->rc;
+  int resize_now = 0;
+  cpi->resize_scale_num = 1;
+  cpi->resize_scale_den = 1;
+  // Don't resize on key frame; reset the counters on key frame.
+  if (cm->frame_type == KEY_FRAME) {
+    cpi->resize_avg_qp = 0;
+    cpi->resize_count = 0;
+    return 0;
+  }
+  // Resize based on average QP over some window.
+  // Ignore samples close to key frame, since QP is usually high after key.
+  if (cpi->rc.frames_since_key > 2 * cpi->framerate) {
+    const int window = 5 * cpi->framerate;
+    cpi->resize_avg_qp += cm->base_qindex;
+    if (cpi->rc.buffer_level < 0)
+      ++cpi->resize_buffer_underflow;
+    ++cpi->resize_count;
+    // Check for resize action every "window" frames.
+    if (cpi->resize_count == window) {
+      int avg_qp = cpi->resize_avg_qp / cpi->resize_count;
+      // Resize down if buffer level has underflowed sufficent amount in past
+      // window, and we are at original resolution.
+      // Resize back up if average QP is low, and we are currently in a resized
+      // down state.
+      if (cpi->resize_state == 0 &&
+          cpi->resize_buffer_underflow > (cpi->resize_count >> 3)) {
+        resize_now = 1;
+      } else if (cpi->resize_state == 1 &&
+                 avg_qp < 40 * cpi->rc.worst_quality / 100) {
+        resize_now = -1;
+      }
+      // Reset for next window measurement.
+      cpi->resize_avg_qp = 0;
+      cpi->resize_count = 0;
+      cpi->resize_buffer_underflow = 0;
+    }
+  }
+  // If decision is to resize, reset some quantities, and check is we should
+  // reduce rate correction factor,
+  if (resize_now != 0) {
+    int target_bits_per_frame;
+    int active_worst_quality;
+    int qindex;
+    int tot_scale_change;
+    // For now, resize is by 1/2 x 1/2.
+    cpi->resize_scale_num = 1;
+    cpi->resize_scale_den = 2;
+    tot_scale_change = (cpi->resize_scale_den * cpi->resize_scale_den) /
+        (cpi->resize_scale_num * cpi->resize_scale_num);
+    // Reset buffer level to optimal, update target size.
+    rc->buffer_level = rc->optimal_buffer_level;
+    rc->bits_off_target = rc->optimal_buffer_level;
+    rc->this_frame_target = calc_pframe_target_size_one_pass_cbr(cpi);
+    // Reset cyclic refresh parameters.
+    if (cpi->oxcf.aq_mode == CYCLIC_REFRESH_AQ && cm->seg.enabled)
+      vp9_cyclic_refresh_reset_resize(cpi);
+    // Get the projected qindex, based on the scaled target frame size (scaled
+    // so target_bits_per_mb in vp9_rc_regulate_q will be correct target).
+    target_bits_per_frame = (resize_now == 1) ?
+        rc->this_frame_target * tot_scale_change :
+        rc->this_frame_target / tot_scale_change;
+    active_worst_quality = calc_active_worst_quality_one_pass_cbr(cpi);
+    qindex = vp9_rc_regulate_q(cpi,
+                               target_bits_per_frame,
+                               rc->best_quality,
+                               active_worst_quality);
+    // If resize is down, check if projected q index is close to worst_quality,
+    // and if so, reduce the rate correction factor (since likely can afford
+    // lower q for resized frame).
+    if (resize_now == 1 &&
+        qindex > 90 * cpi->rc.worst_quality / 100) {
+      rc->rate_correction_factors[INTER_NORMAL] *= 0.85;
+    }
+    // If resize is back up, check if projected q index is too much above the
+    // current base_qindex, and if so, reduce the rate correction factor
+    // (since prefer to keep q for resized frame at least close to previous q).
+    if (resize_now == -1 &&
+       qindex > 130 * cm->base_qindex / 100) {
+      rc->rate_correction_factors[INTER_NORMAL] *= 0.9;
+    }
+  }
+  return resize_now;
+}

vp9/encoder/vp9_ratectrl.h

@@ -245,6 +245,8 @@ void vp9_rc_set_gf_interval_range(const struct VP9_COMP *const cpi,
 
 void vp9_set_target_rate(struct VP9_COMP *cpi);
 
+int vp9_resize_one_pass_cbr(struct VP9_COMP *cpi);
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif