1 /*
2  *  Copyright (c) 2012 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_RTP_RTCP_SOURCE_ULPFEC_GENERATOR_H_
12 #define MODULES_RTP_RTCP_SOURCE_ULPFEC_GENERATOR_H_
13 
14 #include <stddef.h>
15 #include <stdint.h>
16 
17 #include <list>
18 #include <memory>
19 #include <vector>
20 
21 #include "modules/include/module_fec_types.h"
22 #include "modules/rtp_rtcp/source/forward_error_correction.h"
23 #include "modules/rtp_rtcp/source/video_fec_generator.h"
24 #include "rtc_base/race_checker.h"
25 #include "rtc_base/rate_statistics.h"
26 #include "rtc_base/synchronization/mutex.h"
27 
28 namespace webrtc {
29 
30 class FlexfecSender;
31 
32 class UlpfecGenerator : public VideoFecGenerator {
33   friend class FlexfecSender;
34 
35  public:
36   UlpfecGenerator(int red_payload_type, int ulpfec_payload_type, Clock* clock);
37   ~UlpfecGenerator();
38 
GetFecType()39   FecType GetFecType() const override {
40     return VideoFecGenerator::FecType::kUlpFec;
41   }
FecSsrc()42   absl::optional<uint32_t> FecSsrc() override { return absl::nullopt; }
43 
44   void SetProtectionParameters(const FecProtectionParams& delta_params,
45                                const FecProtectionParams& key_params) override;
46 
47   // Adds a media packet to the internal buffer. When enough media packets
48   // have been added, the FEC packets are generated and stored internally.
49   // These FEC packets are then obtained by calling GetFecPacketsAsRed().
50   void AddPacketAndGenerateFec(const RtpPacketToSend& packet) override;
51 
52   // Returns the overhead, per packet, for FEC (and possibly RED).
53   size_t MaxPacketOverhead() const override;
54 
55   std::vector<std::unique_ptr<RtpPacketToSend>> GetFecPackets() override;
56 
57   // Current rate of FEC packets generated, including all RTP-level headers.
58   DataRate CurrentFecRate() const override;
59 
GetRtpState()60   absl::optional<RtpState> GetRtpState() override { return absl::nullopt; }
61 
62  private:
63   struct Params {
64     Params();
65     Params(FecProtectionParams delta_params,
66            FecProtectionParams keyframe_params);
67 
68     FecProtectionParams delta_params;
69     FecProtectionParams keyframe_params;
70   };
71 
72   UlpfecGenerator(std::unique_ptr<ForwardErrorCorrection> fec, Clock* clock);
73 
74   // Overhead is defined as relative to the number of media packets, and not
75   // relative to total number of packets. This definition is inherited from the
76   // protection factor produced by video_coding module and how the FEC
77   // generation is implemented.
78   int Overhead() const;
79 
80   // Returns true if the excess overhead (actual - target) for the FEC is below
81   // the amount |kMaxExcessOverhead|. This effects the lower protection level
82   // cases and low number of media packets/frame. The target overhead is given
83   // by |params_.fec_rate|, and is only achievable in the limit of large number
84   // of media packets.
85   bool ExcessOverheadBelowMax() const;
86 
87   // Returns true if the number of added media packets is at least
88   // |min_num_media_packets_|. This condition tries to capture the effect
89   // that, for the same amount of protection/overhead, longer codes
90   // (e.g. (2k,2m) vs (k,m)) are generally more effective at recovering losses.
91   bool MinimumMediaPacketsReached() const;
92 
93   const FecProtectionParams& CurrentParams() const;
94 
95   void ResetState();
96 
97   const int red_payload_type_;
98   const int ulpfec_payload_type_;
99   Clock* const clock_;
100 
101   rtc::RaceChecker race_checker_;
102   const std::unique_ptr<ForwardErrorCorrection> fec_
103       RTC_GUARDED_BY(race_checker_);
104   ForwardErrorCorrection::PacketList media_packets_
105       RTC_GUARDED_BY(race_checker_);
106   absl::optional<RtpPacketToSend> last_media_packet_
107       RTC_GUARDED_BY(race_checker_);
108   std::list<ForwardErrorCorrection::Packet*> generated_fec_packets_
109       RTC_GUARDED_BY(race_checker_);
110   int num_protected_frames_ RTC_GUARDED_BY(race_checker_);
111   int min_num_media_packets_ RTC_GUARDED_BY(race_checker_);
112   Params current_params_ RTC_GUARDED_BY(race_checker_);
113   bool keyframe_in_process_ RTC_GUARDED_BY(race_checker_);
114 
115   mutable Mutex mutex_;
116   absl::optional<Params> pending_params_ RTC_GUARDED_BY(mutex_);
117   RateStatistics fec_bitrate_ RTC_GUARDED_BY(mutex_);
118 };
119 
120 }  // namespace webrtc
121 
122 #endif  // MODULES_RTP_RTCP_SOURCE_ULPFEC_GENERATOR_H_
123