Utilize bitrate above codec max to protect video.

webrtc/modules/video_coding/main/source/media_optimization.cc

Index: webrtc/modules/video_coding/main/source/media_optimization.cc
diff --git a/webrtc/modules/video_coding/main/source/media_optimization.cc b/webrtc/modules/video_coding/main/source/media_optimization.cc
index 327c8b4b5719048bccbf98f73c9f0c0094b75862..4c987a05132da52040326bf2d332215890a50227 100644
--- a/webrtc/modules/video_coding/main/source/media_optimization.cc
+++ b/webrtc/modules/video_coding/main/source/media_optimization.cc
@@ -204,12 +204,6 @@ uint32_t MediaOptimization::SetTargetRates(
     VCMProtectionCallback* protection_callback,
     VCMQMSettingsCallback* qmsettings_callback) {
   CriticalSectionScoped lock(crit_sect_.get());
-  // TODO(holmer): Consider putting this threshold only on the video bitrate,
-  // and not on protection.
-  if (max_bit_rate_ > 0 &&
-      target_bitrate > static_cast<uint32_t>(max_bit_rate_)) {
-    target_bitrate = max_bit_rate_;
-  }
   VCMProtectionMethod* selected_method = loss_prot_logic_->SelectedMethod();
   float target_bitrate_kbps = static_cast<float>(target_bitrate) / 1000.0f;
   loss_prot_logic_->UpdateBitRate(target_bitrate_kbps);
@@ -241,7 +235,7 @@ uint32_t MediaOptimization::SetTargetRates(
   loss_prot_logic_->UpdateFilteredLossPr(packet_loss_enc);
 
   // Rate cost of the protection methods.
-  uint32_t protection_overhead_bps = 0;
+  float protection_overhead_rate = 0.0f;
 
   // Update protection settings, when applicable.
   float sent_video_rate_kbps = 0.0f;
@@ -273,15 +267,15 @@ uint32_t MediaOptimization::SetTargetRates(
     // Estimate the overhead costs of the next second as staying the same
     // wrt the source bitrate.
     if (sent_total_rate_bps > 0) {
-      protection_overhead_bps = static_cast<uint32_t>(
-          target_bitrate *
-              static_cast<double>(sent_nack_rate_bps + sent_fec_rate_bps) /
-              sent_total_rate_bps +
-          0.5);
+      protection_overhead_rate =
+          static_cast<float>(sent_nack_rate_bps + sent_fec_rate_bps) /
+          sent_total_rate_bps;
     }
+    // TODO(pbos): Does this make sense? NACK retransmissions + FEC overhead can
+    // go above 50% with FEC maxed out.

[stefan-webrtc, 2015/10/29 07:11:15]

I don't think it does. Please remove.

[pbos-webrtc, 2015/10/29 16:40:42]

Done.

     // Cap the overhead estimate to 50%.
-    if (protection_overhead_bps > target_bitrate / 2)
-      protection_overhead_bps = target_bitrate / 2;
+    if (protection_overhead_rate > 0.5)
+      protection_overhead_rate = 0.5;
 
     // Get the effective packet loss for encoder ER when applicable. Should be
     // passed to encoder via fraction_lost.
@@ -290,7 +284,13 @@ uint32_t MediaOptimization::SetTargetRates(
   }
 
   // Source coding rate: total rate - protection overhead.
-  target_bit_rate_ = target_bitrate - protection_overhead_bps;
+  printf("protection_overhead_bps: %f\n", protection_overhead_rate);

[stefan-webrtc, 2015/10/29 07:11:15]

Please remove!

[pbos-webrtc, 2015/10/29 16:40:42]

Done.

+  target_bit_rate_ = target_bitrate * (1.0 - protection_overhead_rate);

[stefan-webrtc, 2015/10/29 07:11:15]

Name this video_target_bitrate_

[pbos-webrtc, 2015/10/29 16:40:42]

Done.

+
+  // Cap target video bitrate to codec maximum.
+  if (max_bit_rate_ > 0 && target_bit_rate_ > max_bit_rate_) {
+    target_bit_rate_ = max_bit_rate_;
+  }
 
   // Update encoding rates following protection settings.
   float target_video_bitrate_kbps =