webrtc/modules/pacing/bitrate_prober.h

/*
 *  Copyright (c) 2014 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.
 */

#ifndef WEBRTC_MODULES_PACING_BITRATE_PROBER_H_
#define WEBRTC_MODULES_PACING_BITRATE_PROBER_H_

#include <cstddef>
#include <list>

#include "webrtc/typedefs.h"

namespace webrtc {

// Note that this class isn't thread-safe by itself and therefore relies
// on being protected by the caller.
class BitrateProber {
 public:
  BitrateProber();

  void SetEnabled(bool enable);

  // Returns true if the prober is in a probing session, i.e., it currently
  // wants packets to be sent out according to the time returned by
  // TimeUntilNextProbe().
  bool IsProbing() const;

  // Initializes a new probing session if the prober is allowed to probe. Does
  // not initialize the prober unless the packet size is large enough to probe
  // with.
  void OnIncomingPacket(uint32_t bitrate_bps,
                        size_t packet_size,
                        int64_t now_ms);

  // Returns the number of milliseconds until the next packet should be sent to
  // get accurate probing.
  int TimeUntilNextProbe(int64_t now_ms);

  // Returns the number of bytes that the prober recommends for the next probe
  // packet.
  size_t RecommendedPacketSize() const;

  // Called to report to the prober that a packet has been sent, which helps the
  // prober know when to move to the next packet in a probe.
  void PacketSent(int64_t now_ms, size_t packet_size);

 private:
  enum ProbingState { kDisabled, kAllowedToProbe, kProbing, kWait };

  ProbingState probing_state_;
  // Probe bitrate per packet. These are used to compute the delta relative to
  // the previous probe packet based on the size and time when that packet was
  // sent.
  std::list<uint32_t> probe_bitrates_;
  size_t packet_size_last_send_;
  int64_t time_last_send_ms_;
};
}  // namespace webrtc
#endif  // WEBRTC_MODULES_PACING_BITRATE_PROBER_H_