1 /*
2  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef WEBRTC_MODULES_PACING_BITRATE_PROBER_H_
12 #define WEBRTC_MODULES_PACING_BITRATE_PROBER_H_
13 
14 #include <queue>
15 
16 #include "webrtc/base/basictypes.h"
17 #include "webrtc/typedefs.h"
18 
19 namespace webrtc {
20 
21 // Note that this class isn't thread-safe by itself and therefore relies
22 // on being protected by the caller.
23 class BitrateProber {
24  public:
25   BitrateProber();
26 
27   void SetEnabled(bool enable);
28 
29   // Returns true if the prober is in a probing session, i.e., it currently
30   // wants packets to be sent out according to the time returned by
31   // TimeUntilNextProbe().
32   bool IsProbing() const;
33 
34   // Initializes a new probing session if the prober is allowed to probe. Does
35   // not initialize the prober unless the packet size is large enough to probe
36   // with.
37   void OnIncomingPacket(size_t packet_size);
38 
39   // Create a cluster used to probe for |bitrate_bps| with |num_probes| number
40   // of probes.
41   void CreateProbeCluster(int bitrate_bps);
42 
43   // Returns the number of milliseconds until the next probe should be sent to
44   // get accurate probing.
45   int TimeUntilNextProbe(int64_t now_ms);
46 
47   // Which cluster that is currently being used for probing.
48   int CurrentClusterId() const;
49 
50   // Returns the minimum number of bytes that the prober recommends for
51   // the next probe.
52   size_t RecommendedMinProbeSize() const;
53 
54   // Called to report to the prober that a probe has been sent. In case of
55   // multiple packets per probe, this call would be made at the end of sending
56   // the last packet in probe. |probe_size| is the total size of all packets
57   // in probe.
58   void ProbeSent(int64_t now_ms, size_t probe_size);
59 
60  private:
61   enum class ProbingState {
62     // Probing will not be triggered in this state at all times.
63     kDisabled,
64     // Probing is enabled and ready to trigger on the first packet arrival.
65     kInactive,
66     // Probe cluster is filled with the set of data rates to be probed and
67     // probes are being sent.
68     kActive,
69     // Probing is enabled, but currently suspended until an explicit trigger
70     // to start probing again.
71     kSuspended,
72   };
73 
74   // A probe cluster consists of a set of probes. Each probe in turn can be
75   // divided into a number of packets to accomodate the MTU on the network.
76   struct ProbeCluster {
77     int min_probes = 0;
78     int sent_probes = 0;
79     int min_bytes = 0;
80     int sent_bytes = 0;
81     int bitrate_bps = 0;
82     int id = -1;
83   };
84 
85   // Resets the state of the prober and clears any cluster/timing data tracked.
86   void ResetState();
87 
88   ProbingState probing_state_;
89   // Probe bitrate per packet. These are used to compute the delta relative to
90   // the previous probe packet based on the size and time when that packet was
91   // sent.
92   std::queue<ProbeCluster> clusters_;
93   // A probe can include one or more packets.
94   size_t probe_size_last_sent_;
95   // The last time a probe was sent.
96   int64_t time_last_probe_sent_ms_;
97   int next_cluster_id_;
98 };
99 }  // namespace webrtc
100 #endif  // WEBRTC_MODULES_PACING_BITRATE_PROBER_H_
101