Allow pacer to boost bitrate in order to meet time constraints.

webrtc/modules/pacing/paced_sender.h

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 33 matching lines @@
                                   int64_t capture_time_ms,
                                   bool retransmission) = 0;
     // Called when it's a good time to send a padding data.
     // Returns the number of bytes sent.
     virtual size_t TimeToSendPadding(size_t bytes) = 0;
 
    protected:
     virtual ~Callback() {}
   };
 
-  static const int64_t kDefaultMaxQueueLengthMs = 2000;
+  // Expected max pacer delay in ms. If ExpectedQueueTimeMs() is higher than
+  // this value, the packet producers should wait (eg drop frames rather than
+  // encoding them). Bitrate sent may temporarily exceed target set by
+  // UpdateBitrate() so that this limit will be upheld.
+  static const int64_t kMaxQueueLengthMs;
   // Pace in kbits/s until we receive first estimate.
   static const int kDefaultInitialPaceKbps = 2000;
   // Pacing-rate relative to our target send rate.
   // Multiplicative factor that is applied to the target bitrate to calculate
   // the number of bytes that can be transmitted per interval.
   // Increasing this factor will result in lower delays in cases of bitrate
   // overshoots from the encoder.
   static const float kDefaultPaceMultiplier;
 
   static const size_t kMinProbePacketSize = 200;
@@ skipping 70 matching lines @@
   // we can pace out during the current interval.
   rtc::scoped_ptr<paced_sender::IntervalBudget> media_budget_
       GUARDED_BY(critsect_);
   // This is the padding budget, keeping track of how many bits of padding we're
   // allowed to send out during the current interval. This budget will be
   // utilized when there's no media to send.
   rtc::scoped_ptr<paced_sender::IntervalBudget> padding_budget_
       GUARDED_BY(critsect_);
 
   rtc::scoped_ptr<BitrateProber> prober_ GUARDED_BY(critsect_);
+  // Actual configured bitrates (media_budget_ may temporarily be higher in
+  // order to meet pace time constraint).
   int bitrate_bps_ GUARDED_BY(critsect_);
+  int max_bitrate_kbps_ GUARDED_BY(critsect_);
 
   int64_t time_last_update_us_ GUARDED_BY(critsect_);
 
   rtc::scoped_ptr<paced_sender::PacketQueue> packets_ GUARDED_BY(critsect_);
   uint64_t packet_counter_;
 };
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_PACING_PACED_SENDER_H_