tor-browser

The Tor Browser
git clone https://git.dasho.dev/tor-browser.git
Log | Files | Refs | README | LICENSE

ulpfec_generator.h (4821B)

      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 <optional>
     20 #include <vector>
     21 
     22 #include "api/environment/environment.h"
     23 #include "api/units/data_rate.h"
     24 #include "modules/include/module_fec_types.h"
     25 #include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
     26 #include "modules/rtp_rtcp/source/forward_error_correction.h"
     27 #include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
     28 #include "modules/rtp_rtcp/source/video_fec_generator.h"
     29 #include "rtc_base/bitrate_tracker.h"
     30 #include "rtc_base/race_checker.h"
     31 #include "rtc_base/synchronization/mutex.h"
     32 #include "rtc_base/thread_annotations.h"
     33 
     34 namespace webrtc {
     35 
     36 class FlexfecSender;
     37 
     38 class UlpfecGenerator : public VideoFecGenerator {
     39  friend class FlexfecSender;
     40 
     41 public:
     42  UlpfecGenerator(const Environment& env,
     43                  int red_payload_type,
     44                  int ulpfec_payload_type);
     45  ~UlpfecGenerator();
     46 
     47  FecType GetFecType() const override {
     48    return VideoFecGenerator::FecType::kUlpFec;
     49  }
     50  std::optional<uint32_t> FecSsrc() override { return std::nullopt; }
     51 
     52  void SetProtectionParameters(const FecProtectionParams& delta_params,
     53                               const FecProtectionParams& key_params) override;
     54 
     55  // Adds a media packet to the internal buffer. When enough media packets
     56  // have been added, the FEC packets are generated and stored internally.
     57  // These FEC packets are then obtained by calling GetFecPacketsAsRed().
     58  void AddPacketAndGenerateFec(const RtpPacketToSend& packet) override;
     59 
     60  // Returns the overhead, per packet, for FEC (and possibly RED).
     61  size_t MaxPacketOverhead() const override;
     62 
     63  std::vector<std::unique_ptr<RtpPacketToSend>> GetFecPackets() override;
     64 
     65  // Current rate of FEC packets generated, including all RTP-level headers.
     66  DataRate CurrentFecRate() const override;
     67 
     68  std::optional<RtpState> GetRtpState() override { return std::nullopt; }
     69 
     70  // Currently used protection params.
     71  const FecProtectionParams& CurrentParams() const;
     72 
     73 private:
     74  struct Params {
     75    Params();
     76    Params(FecProtectionParams delta_params,
     77           FecProtectionParams keyframe_params);
     78 
     79    FecProtectionParams delta_params;
     80    FecProtectionParams keyframe_params;
     81  };
     82 
     83  UlpfecGenerator(const Environment& env,
     84                  std::unique_ptr<ForwardErrorCorrection> fec);
     85 
     86  // Overhead is defined as relative to the number of media packets, and not
     87  // relative to total number of packets. This definition is inherited from the
     88  // protection factor produced by video_coding module and how the FEC
     89  // generation is implemented.
     90  int Overhead() const;
     91 
     92  // Returns true if the excess overhead (actual - target) for the FEC is below
     93  // the amount `kMaxExcessOverhead`. This effects the lower protection level
     94  // cases and low number of media packets/frame. The target overhead is given
     95  // by `params_.fec_rate`, and is only achievable in the limit of large number
     96  // of media packets.
     97  bool ExcessOverheadBelowMax() const;
     98 
     99  // Returns true if the number of added media packets is at least
    100  // `min_num_media_packets_`. This condition tries to capture the effect
    101  // that, for the same amount of protection/overhead, longer codes
    102  // (e.g. (2k,2m) vs (k,m)) are generally more effective at recovering losses.
    103  bool MinimumMediaPacketsReached() const;
    104 
    105  void ResetState();
    106 
    107  const Environment env_;
    108  const int red_payload_type_;
    109  const int ulpfec_payload_type_;
    110 
    111  RaceChecker race_checker_;
    112  const std::unique_ptr<ForwardErrorCorrection> fec_
    113      RTC_GUARDED_BY(race_checker_);
    114  ForwardErrorCorrection::PacketList media_packets_
    115      RTC_GUARDED_BY(race_checker_);
    116  std::optional<RtpPacketToSend> last_media_packet_
    117      RTC_GUARDED_BY(race_checker_);
    118  std::list<ForwardErrorCorrection::Packet*> generated_fec_packets_
    119      RTC_GUARDED_BY(race_checker_);
    120  int num_protected_frames_ RTC_GUARDED_BY(race_checker_);
    121  int min_num_media_packets_ RTC_GUARDED_BY(race_checker_);
    122  Params current_params_ RTC_GUARDED_BY(race_checker_);
    123  bool media_contains_keyframe_ RTC_GUARDED_BY(race_checker_);
    124 
    125  mutable Mutex mutex_;
    126  std::optional<Params> pending_params_ RTC_GUARDED_BY(mutex_);
    127  BitrateTracker fec_bitrate_ RTC_GUARDED_BY(mutex_);
    128 };
    129 
    130 }  // namespace webrtc
    131 
    132 #endif  // MODULES_RTP_RTCP_SOURCE_ULPFEC_GENERATOR_H_