1 /*
2  *  Copyright (c) 2013 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 MODULES_REMOTE_BITRATE_ESTIMATOR_INTER_ARRIVAL_H_
12 #define MODULES_REMOTE_BITRATE_ESTIMATOR_INTER_ARRIVAL_H_
13 
14 #include <stddef.h>
15 #include <stdint.h>
16 
17 #include "rtc_base/constructor_magic.h"
18 
19 namespace webrtc {
20 
21 // Helper class to compute the inter-arrival time delta and the size delta
22 // between two timestamp groups. A timestamp is a 32 bit unsigned number with
23 // a client defined rate.
24 class InterArrival {
25  public:
26   // After this many packet groups received out of order InterArrival will
27   // reset, assuming that clocks have made a jump.
28   static constexpr int kReorderedResetThreshold = 3;
29   static constexpr int64_t kArrivalTimeOffsetThresholdMs = 3000;
30 
31   // A timestamp group is defined as all packets with a timestamp which are at
32   // most timestamp_group_length_ticks older than the first timestamp in that
33   // group.
34   InterArrival(uint32_t timestamp_group_length_ticks,
35                double timestamp_to_ms_coeff,
36                bool enable_burst_grouping);
37 
38   // This function returns true if a delta was computed, or false if the current
39   // group is still incomplete or if only one group has been completed.
40   // |timestamp| is the timestamp.
41   // |arrival_time_ms| is the local time at which the packet arrived.
42   // |packet_size| is the size of the packet.
43   // |timestamp_delta| (output) is the computed timestamp delta.
44   // |arrival_time_delta_ms| (output) is the computed arrival-time delta.
45   // |packet_size_delta| (output) is the computed size delta.
46   bool ComputeDeltas(uint32_t timestamp,
47                      int64_t arrival_time_ms,
48                      int64_t system_time_ms,
49                      size_t packet_size,
50                      uint32_t* timestamp_delta,
51                      int64_t* arrival_time_delta_ms,
52                      int* packet_size_delta);
53 
54  private:
55   struct TimestampGroup {
TimestampGroupTimestampGroup56     TimestampGroup()
57         : size(0),
58           first_timestamp(0),
59           timestamp(0),
60           first_arrival_ms(-1),
61           complete_time_ms(-1) {}
62 
IsFirstPacketTimestampGroup63     bool IsFirstPacket() const { return complete_time_ms == -1; }
64 
65     size_t size;
66     uint32_t first_timestamp;
67     uint32_t timestamp;
68     int64_t first_arrival_ms;
69     int64_t complete_time_ms;
70     int64_t last_system_time_ms;
71   };
72 
73   // Returns true if the packet with timestamp |timestamp| arrived in order.
74   bool PacketInOrder(uint32_t timestamp);
75 
76   // Returns true if the last packet was the end of the current batch and the
77   // packet with |timestamp| is the first of a new batch.
78   bool NewTimestampGroup(int64_t arrival_time_ms, uint32_t timestamp) const;
79 
80   bool BelongsToBurst(int64_t arrival_time_ms, uint32_t timestamp) const;
81 
82   void Reset();
83 
84   const uint32_t kTimestampGroupLengthTicks;
85   TimestampGroup current_timestamp_group_;
86   TimestampGroup prev_timestamp_group_;
87   double timestamp_to_ms_coeff_;
88   bool burst_grouping_;
89   int num_consecutive_reordered_packets_;
90 
91   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(InterArrival);
92 };
93 }  // namespace webrtc
94 
95 #endif  // MODULES_REMOTE_BITRATE_ESTIMATOR_INTER_ARRIVAL_H_
96