DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Header

Mercurial (cdf352f02ac4)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
/*
 *  Copyright (c) 2016 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.
 */

#include "modules/video_coding/protection_bitrate_calculator.h"

namespace webrtc {

using rtc::CritScope;

struct ProtectionBitrateCalculator::EncodedFrameSample {
  EncodedFrameSample(size_t size_bytes,
                     uint32_t timestamp,
                     int64_t time_complete_ms)
      : size_bytes(size_bytes),
        timestamp(timestamp),
        time_complete_ms(time_complete_ms) {}
  size_t size_bytes;
  uint32_t timestamp;
  int64_t time_complete_ms;
};

ProtectionBitrateCalculator::ProtectionBitrateCalculator(
    Clock* clock,
    VCMProtectionCallback* protection_callback)
    : clock_(clock),
      protection_callback_(protection_callback),
      loss_prot_logic_(new media_optimization::VCMLossProtectionLogic(
          clock_->TimeInMilliseconds())),
      max_payload_size_(1460) {}

ProtectionBitrateCalculator::~ProtectionBitrateCalculator(void) {
  loss_prot_logic_->Release();
}

void ProtectionBitrateCalculator::SetEncodingData(size_t width,
                                                  size_t height,
                                                  size_t num_temporal_layers,
                                                  size_t max_payload_size) {
  CritScope lock(&crit_sect_);
  loss_prot_logic_->UpdateFrameSize(width, height);
  loss_prot_logic_->UpdateNumLayers(num_temporal_layers);
  max_payload_size_ = max_payload_size;
}

uint32_t ProtectionBitrateCalculator::SetTargetRates(
    uint32_t estimated_bitrate_bps,
    int actual_framerate_fps,
    uint8_t fraction_lost,
    int64_t round_trip_time_ms) {
  float target_bitrate_kbps =
      static_cast<float>(estimated_bitrate_bps) / 1000.0f;
  // Sanity check.
  if (actual_framerate_fps < 1.0) {
    actual_framerate_fps = 1.0;
  }

  FecProtectionParams delta_fec_params;
  FecProtectionParams key_fec_params;
  {
    CritScope lock(&crit_sect_);

    loss_prot_logic_->UpdateBitRate(target_bitrate_kbps);
    loss_prot_logic_->UpdateRtt(round_trip_time_ms);

    // Update frame rate for the loss protection logic class: frame rate should
    // be the actual/sent rate.
    loss_prot_logic_->UpdateFrameRate(actual_framerate_fps);

    // Returns the filtered packet loss, used for the protection setting.
    // The filtered loss may be the received loss (no filter), or some
    // filtered value (average or max window filter).
    // Use max window filter for now.
    media_optimization::FilterPacketLossMode filter_mode =
        media_optimization::kMaxFilter;
    uint8_t packet_loss_enc = loss_prot_logic_->FilteredLoss(
        clock_->TimeInMilliseconds(), filter_mode, fraction_lost);

    // For now use the filtered loss for computing the robustness settings.
    loss_prot_logic_->UpdateFilteredLossPr(packet_loss_enc);

    if (loss_prot_logic_->SelectedType() == media_optimization::kNone) {
      return estimated_bitrate_bps;
    }

    // Update method will compute the robustness settings for the given
    // protection method and the overhead cost
    // the protection method is set by the user via SetVideoProtection.
    loss_prot_logic_->UpdateMethod();

    // Get the bit cost of protection method, based on the amount of
    // overhead data actually transmitted (including headers) the last
    // second.

    // Get the FEC code rate for Key frames (set to 0 when NA).
    key_fec_params.fec_rate =
        loss_prot_logic_->SelectedMethod()->RequiredProtectionFactorK();

    // Get the FEC code rate for Delta frames (set to 0 when NA).
    delta_fec_params.fec_rate =
        loss_prot_logic_->SelectedMethod()->RequiredProtectionFactorD();

    // The RTP module currently requires the same |max_fec_frames| for both
    // key and delta frames.
    delta_fec_params.max_fec_frames =
        loss_prot_logic_->SelectedMethod()->MaxFramesFec();
    key_fec_params.max_fec_frames =
        loss_prot_logic_->SelectedMethod()->MaxFramesFec();
  }

  // Set the FEC packet mask type. |kFecMaskBursty| is more effective for
  // consecutive losses and little/no packet re-ordering. As we currently
  // do not have feedback data on the degree of correlated losses and packet
  // re-ordering, we keep default setting to |kFecMaskRandom| for now.
  delta_fec_params.fec_mask_type = kFecMaskRandom;
  key_fec_params.fec_mask_type = kFecMaskRandom;

  // Update protection callback with protection settings.
  uint32_t sent_video_rate_bps = 0;
  uint32_t sent_nack_rate_bps = 0;
  uint32_t sent_fec_rate_bps = 0;
  // Rate cost of the protection methods.
  float protection_overhead_rate = 0.0f;

  // TODO(Marco): Pass FEC protection values per layer.
  protection_callback_->ProtectionRequest(
      &delta_fec_params, &key_fec_params, &sent_video_rate_bps,
      &sent_nack_rate_bps, &sent_fec_rate_bps);

  uint32_t sent_total_rate_bps =
      sent_video_rate_bps + sent_nack_rate_bps + sent_fec_rate_bps;
  // Estimate the overhead costs of the next second as staying the same
  // wrt the source bitrate.
  if (sent_total_rate_bps > 0) {
    protection_overhead_rate =
        static_cast<float>(sent_nack_rate_bps + sent_fec_rate_bps) /
        sent_total_rate_bps;
  }
  // Cap the overhead estimate to 50%.
  if (protection_overhead_rate > 0.5)
    protection_overhead_rate = 0.5;

  // Source coding rate: total rate - protection overhead.
  return estimated_bitrate_bps * (1.0 - protection_overhead_rate);
}

void ProtectionBitrateCalculator::SetProtectionMethod(bool enable_fec,
                                                      bool enable_nack) {
  media_optimization::VCMProtectionMethodEnum method(media_optimization::kNone);
  if (enable_fec && enable_nack) {
    method = media_optimization::kNackFec;
  } else if (enable_nack) {
    method = media_optimization::kNack;
  } else if (enable_fec) {
    method = media_optimization::kFec;
  }
  CritScope lock(&crit_sect_);
  loss_prot_logic_->SetMethod(method);
}

void ProtectionBitrateCalculator::UpdateWithEncodedData(
    const EncodedImage& encoded_image) {
  const size_t encoded_length = encoded_image._length;
  CritScope lock(&crit_sect_);
  if (encoded_length > 0) {
    const bool delta_frame = encoded_image._frameType != kVideoFrameKey;

    if (max_payload_size_ > 0 && encoded_length > 0) {
      const float min_packets_per_frame =
          encoded_length / static_cast<float>(max_payload_size_);
      if (delta_frame) {
        loss_prot_logic_->UpdatePacketsPerFrame(min_packets_per_frame,
                                                clock_->TimeInMilliseconds());
      } else {
        loss_prot_logic_->UpdatePacketsPerFrameKey(
            min_packets_per_frame, clock_->TimeInMilliseconds());
      }
    }
    if (!delta_frame && encoded_length > 0) {
      loss_prot_logic_->UpdateKeyFrameSize(static_cast<float>(encoded_length));
    }
  }
}

}  // namespace webrtc