Probing: Add support for exponential startup probing

webrtc/modules/pacing/paced_sender.h

Index: webrtc/modules/pacing/paced_sender.h
diff --git a/webrtc/modules/pacing/paced_sender.h b/webrtc/modules/pacing/paced_sender.h
index c904d4b6b77d1db50dcd23a7ba41e921651d5052..0547182755edf1dfc487f82c48c31d9c7d02df77 100644
--- a/webrtc/modules/pacing/paced_sender.h
+++ b/webrtc/modules/pacing/paced_sender.h
@@ -12,9 +12,11 @@
 #define WEBRTC_MODULES_PACING_PACED_SENDER_H_
 
 #include <list>
+#include <map>
 #include <memory>
 #include <set>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
@@ -33,6 +35,13 @@ class PacketQueue;
 
 class PacedSender : public Module, public RtpPacketSender {
  public:
+  enum class State {
+    kInit,
+    kWaitForProbingResult,
+    kStartupProbing,
+    kNormal,
+  };
+
   class PacketSender {
    public:
     // Note: packets sent as a result of a callback should not pass by this
@@ -64,7 +73,10 @@ class PacedSender : public Module, public RtpPacketSender {
   // overshoots from the encoder.
   static const float kDefaultPaceMultiplier;
 
-  static const size_t kMinProbePacketSize = 200;
+  // TODO(isheriff): Large enough to allow measurements up-to 7 Mbps.
+  // This requirement will go away when we cluster multiple packets as a single
+  // probe.
+  static const size_t kMinProbePacketSize = 1000;

[stefan-webrtc, 2016/08/16 11:27:04]

I'm not sure about introducing this change. It will break the behavior at low
bitrates, e.g., if the bitrate is set to 300 kbps we may never have 1000 bytes
packets.

[Irfan, 2016/08/16 18:12:47]

I will go ahead and revert this. Since I plan to add support for multiple
packets per probe, this should not be needed.

 
   PacedSender(Clock* clock,
               PacketSender* packet_sender);
@@ -87,7 +99,7 @@ class PacedSender : public Module, public RtpPacketSender {
   // |bitrate_bps| is our estimate of what we are allowed to send on average.
   // We will pace out bursts of packets at a bitrate of
   // |bitrate_bps| * kDefaultPaceMultiplier.
-  virtual void SetEstimatedBitrate(uint32_t bitrate_bps);
+  virtual void SetEstimatedBitrate(int bitrate_bps);
 
   // Sets the minimum send bitrate and maximum padding bitrate requested by send
   // streams.
@@ -128,6 +140,9 @@ class PacedSender : public Module, public RtpPacketSender {
   // Process any pending packets in the queue(s).
   void Process() override;
 
+  State PacingState();
+  void OnProbingBitrateMeasured(int bitrate_bps);
+
  private:
   // Updates the number of bytes that can be sent for the next time interval.
   void UpdateBytesPerInterval(int64_t delta_time_in_ms)
@@ -156,15 +171,21 @@ class PacedSender : public Module, public RtpPacketSender {
   std::unique_ptr<BitrateProber> prober_ GUARDED_BY(critsect_);
   // Actual configured bitrates (media_budget_ may temporarily be higher in
   // order to meet pace time constraint).
-  uint32_t estimated_bitrate_bps_ GUARDED_BY(critsect_);
-  uint32_t min_send_bitrate_kbps_ GUARDED_BY(critsect_);
-  uint32_t max_padding_bitrate_kbps_ GUARDED_BY(critsect_);
-  uint32_t pacing_bitrate_kbps_ GUARDED_BY(critsect_);
+  int estimated_bitrate_bps_ GUARDED_BY(critsect_);
+  int min_send_bitrate_kbps_ GUARDED_BY(critsect_);
+  int max_padding_bitrate_kbps_ GUARDED_BY(critsect_);
+  int pacing_bitrate_kbps_ GUARDED_BY(critsect_);
 
   int64_t time_last_update_us_ GUARDED_BY(critsect_);
 
   std::unique_ptr<paced_sender::PacketQueue> packets_ GUARDED_BY(critsect_);
   uint64_t packet_counter_;
+  // TODO(isheriff): Adding critsect_ gets clang complaints even with
+  // critsect_ protection turned on!
+  State pacing_state_;
+  int64_t start_time_wait_probe_result_ms_ GUARDED_BY(critsect_);
+  int min_bitrate_to_probe_further_ GUARDED_BY(critsect_);
+  int bitrate_below_expected_count_ GUARDED_BY(critsect_) = 0;

[stefan-webrtc, 2016/08/16 11:27:05]

Initialize in initializer list instead.

[Irfan, 2016/08/16 18:12:47]

Will do, but I seem to recall seeing in style this being encouraged (I cant find
it now though)

 };
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_PACING_PACED_SENDER_H_