Fix perf regression in screenshare temporal layer bitrate allocation

webrtc/modules/video_coding/codecs/vp8/screenshare_layers.cc

 /* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */
 
 #include "webrtc/modules/video_coding/codecs/vp8/screenshare_layers.h"
@@ skipping 144 matching lines @@
   // Make sure both frame droppers leak out bits.
   layers_[0].UpdateDebt(ts_diff / 90);
   layers_[1].UpdateDebt(ts_diff / 90);
   last_timestamp_ = timestamp;
   return flags;
 }
 
 std::vector<uint32_t> ScreenshareLayers::OnRatesUpdated(int bitrate_kbps,
                                                         int max_bitrate_kbps,
                                                         int framerate) {
+  bitrate_updated_ =
+      bitrate_kbps != static_cast<int>(layers_[0].target_rate_kbps_) ||
+      max_bitrate_kbps != static_cast<int>(layers_[1].target_rate_kbps_) ||
+      framerate != framerate_;
   layers_[0].target_rate_kbps_ = bitrate_kbps;
   layers_[1].target_rate_kbps_ = max_bitrate_kbps;
   framerate_ = framerate;
-  bitrate_updated_ = true;
 
   std::vector<uint32_t> allocation;
   allocation.push_back(bitrate_kbps);
   if (max_bitrate_kbps > bitrate_kbps)
     allocation.push_back(max_bitrate_kbps - bitrate_kbps);
   return allocation;
 }
 
 void ScreenshareLayers::FrameEncoded(unsigned int size,
                                      uint32_t timestamp,
@@ skipping 76 matching lines @@
     // If too soon from previous sync frame, don't issue a new one.
     return false;
   }
   // Issue a sync frame if difference in quality between TL0 and TL1 isn't too
   // large.
   if (layers_[0].last_qp - layers_[1].last_qp < kQpDeltaThresholdForSync)
     return true;
   return false;
 }
 
+uint32_t ScreenshareLayers::GetCodecTargetBitrateKbps() const {
+  uint32_t target_bitrate_kbps = layers_[0].target_rate_kbps_;
+
+  if (number_of_temporal_layers_ > 1) {
+    // Calculate a codec target bitrate. This may be higher than TL0, gaining
+    // quality at the expense of frame rate at TL0. Constraints:
+    // - TL0 frame rate no less than framerate / kMaxTL0FpsReduction.
+    // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
+    target_bitrate_kbps =
+        std::min(layers_[0].target_rate_kbps_ * kMaxTL0FpsReduction,
+                 layers_[1].target_rate_kbps_ / kAcceptableTargetOvershoot);
+  }
+
+  return std::max(layers_[0].target_rate_kbps_, target_bitrate_kbps);
+}
+
 bool ScreenshareLayers::UpdateConfiguration(vpx_codec_enc_cfg_t* cfg) {
   bool cfg_updated = false;
-  if (bitrate_updated_) {
-    uint32_t target_bitrate_kbps = layers_[0].target_rate_kbps_;
-
-    if (number_of_temporal_layers_ > 1) {
-      // Calculate a codec target bitrate. This may be higher than TL0, gaining
-      // quality at the expense of frame rate at TL0. Constraints:
-      // - TL0 frame rate no less than framerate / kMaxTL0FpsReduction.
-      // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
-      target_bitrate_kbps =
-          std::min(layers_[0].target_rate_kbps_ * kMaxTL0FpsReduction,
-                   layers_[1].target_rate_kbps_ / kAcceptableTargetOvershoot);
-
-      cfg->rc_target_bitrate =
-          std::max(layers_[0].target_rate_kbps_, target_bitrate_kbps);
-    }
+  uint32_t target_bitrate_kbps = GetCodecTargetBitrateKbps();
+  if (bitrate_updated_ || cfg->rc_target_bitrate != target_bitrate_kbps) {
+    cfg->rc_target_bitrate = target_bitrate_kbps;
 
     // Don't reconfigure qp limits during quality boost frames.
     if (active_layer_ == -1 ||
         layers_[active_layer_].state != TemporalLayer::State::kQualityBoost) {
       min_qp_ = cfg->rc_min_quantizer;
       max_qp_ = cfg->rc_max_quantizer;
       // After a dropped frame, a frame with max qp will be encoded and the
       // quality will then ramp up from there. To boost the speed of recovery,
       // encode the next frame with lower max qp. TL0 is the most important to
       // improve since the errors in this layer will propagate to TL1.
@@ skipping 30 matching lines @@
     if (max_qp_ == -1)
       return cfg_updated;
     adjusted_max_qp = max_qp_;  // Set the normal max qp.
   }
 
   if (adjusted_max_qp == cfg->rc_max_quantizer)
     return cfg_updated;
 
   cfg->rc_max_quantizer = adjusted_max_qp;
   cfg_updated = true;
+
   return cfg_updated;
 }
 
 void ScreenshareLayers::TemporalLayer::UpdateDebt(int64_t delta_ms) {
   uint32_t debt_reduction_bytes = target_rate_kbps_ * delta_ms / 8;
   if (debt_reduction_bytes >= debt_bytes_) {
     debt_bytes_ = 0;
   } else {
     debt_bytes_ -= debt_reduction_bytes;
   }
@@ skipping 31 matching lines @@
       RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.Screenshare.Layer1.Qp",
                                  stats_.tl1_qp_sum_ / stats_.num_tl1_frames_);
       RTC_HISTOGRAM_COUNTS_10000(
           "WebRTC.Video.Screenshare.Layer1.TargetBitrate",
           stats_.tl1_target_bitrate_sum_ / stats_.num_tl1_frames_);
     }
   }
 }
 
 }  // namespace webrtc