media/cast/sender/congestion_control.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_CAST_CONGESTION_CONTROL_CONGESTION_CONTROL_H_
   6 #define MEDIA_CAST_CONGESTION_CONTROL_CONGESTION_CONTROL_H_
   7
   8 #include <deque>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/time/tick_clock.h"
  13 #include "base/time/time.h"
  14
  15 namespace media {
  16 namespace cast {
  17
  18 class CongestionControl {
  19  public:
  20   CongestionControl(base::TickClock* clock,
  21                     uint32 max_bitrate_configured,
  22                     uint32 min_bitrate_configured,
  23                     size_t max_unacked_frames);
  24
  25   virtual ~CongestionControl();
  26
  27   void UpdateRtt(base::TimeDelta rtt);
  28
  29   // Called when an encoded frame is sent to the transport.
  30   void SendFrameToTransport(uint32 frame_id,
  31                             size_t frame_size,
  32                             base::TimeTicks when);
  33
  34   // Called when we receive an ACK for a frame.
  35   void AckFrame(uint32 frame_id, base::TimeTicks when);
  36
  37   // Returns the bitrate we should use for the next frame.
  38   uint32 GetBitrate(base::TimeTicks playout_time,
  39                     base::TimeDelta playout_delay);
  40
  41  private:
  42   struct FrameStats {
  43     FrameStats();
  44     // Time this frame was sent to the transport.
  45     base::TimeTicks sent_time;
  46     // Time this frame was acked.
  47     base::TimeTicks ack_time;
  48     // Size of encoded frame in bits.
  49     size_t frame_size;
  50   };
  51
  52   // Calculate how much "dead air" (idle time) there is between two frames.
  53   static base::TimeDelta DeadTime(const FrameStats& a, const FrameStats& b);
  54   // Get the FrameStats for a given |frame_id|.
  55   // Note: Older FrameStats will be removed automatically.
  56   FrameStats* GetFrameStats(uint32 frame_id);
  57   // Calculate a safe bitrate. This is based on how much we've been
  58   // sending in the past.
  59   double CalculateSafeBitrate();
  60
  61   // For a given frame, calculate when it might be acked.
  62   // (Or return the time it was acked, if it was.)
  63   base::TimeTicks EstimatedAckTime(uint32 frame_id, double bitrate);
  64   // Calculate when we start sending the data for a given frame.
  65   // This is done by calculating when we were done sending the previous
  66   // frame, but obviously can't be less than |sent_time| (if known).
  67   base::TimeTicks EstimatedSendingTime(uint32 frame_id, double bitrate);
  68
  69   base::TickClock* const clock_;  // Not owned by this class.
  70   const uint32 max_bitrate_configured_;
  71   const uint32 min_bitrate_configured_;
  72   std::deque<FrameStats> frame_stats_;
  73   uint32 last_frame_stats_;
  74   uint32 last_acked_frame_;
  75   uint32 last_encoded_frame_;
  76   base::TimeDelta rtt_;
  77   size_t history_size_;
  78   size_t acked_bits_in_history_;
  79   base::TimeDelta dead_time_in_history_;
  80
  81   DISALLOW_COPY_AND_ASSIGN(CongestionControl);
  82 };
  83
  84 }  // namespace cast
  85 }  // namespace media
  86
  87 #endif  // MEDIA_CAST_CONGESTION_CONTROL_CONGESTION_CONTROL_H_