BWE allocation strategy

webrtc/rtc_base/bitrateallocationstrategy.cc

+/*
+ *  Copyright 2017 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 "webrtc/rtc_base/bitrateallocationstrategy.h"
+#include <algorithm>
+#include <utility>
+
+namespace rtc {
+
+std::vector<uint32_t> BitrateAllocationStrategy::SetAllBitratesToMinimum(
+    const ArrayView<const TrackConfig*> track_configs) {
+  std::vector<uint32_t> track_allocations;
+  for (const auto* track_config : track_configs) {
+    track_allocations.push_back(track_config->min_bitrate_bps);
+  }
+  return track_allocations;
+}
+
+std::vector<uint32_t> BitrateAllocationStrategy::DistributeBitratesEvenly(
+    const ArrayView<const TrackConfig*> track_configs,
+    uint32_t available_bitrate) {
+  std::vector<uint32_t> track_allocations =
+      SetAllBitratesToMinimum(track_configs);
+  uint32_t sum_min_bitrates = 0;
+  uint32_t sum_max_bitrates = 0;
+  for (const auto* track_config : track_configs) {
+    sum_min_bitrates += track_config->min_bitrate_bps;
+    sum_max_bitrates += track_config->max_bitrate_bps;
+  }
+  if (sum_min_bitrates >= available_bitrate) {
+    return track_allocations;
+  } else if (available_bitrate >= sum_max_bitrates) {
+    auto track_allocations_it = track_allocations.begin();
+    for (const auto* track_config : track_configs) {
+      *track_allocations_it++ = track_config->max_bitrate_bps;
+    }
+    return track_allocations;

[Taylor Brandstetter, 2017/09/11 16:55:06]

Where is "enforce_min_bitrate" used?

[alexnarest, 2017/09/14 13:08:33]

Current implementation does not pause tracks.

[Taylor Brandstetter, 2017/09/15 01:24:41]

Should that be documented in a comment?

[alexnarest, 2017/09/15 08:29:38]

Done.

+  } else {
+    std::multimap<uint32_t, size_t> max_bitrate_sorted_configs;

[Taylor Brandstetter, 2017/09/11 16:55:06]

This logic is a little confusing at first glance; can you add comments where
applicable?

[alexnarest, 2017/09/14 13:08:33]

Done.

+    for (const TrackConfig** track_configs_it = track_configs.begin();
+         track_configs_it != track_configs.end(); track_configs_it++) {
+      max_bitrate_sorted_configs.insert(std::pair<uint32_t, size_t>(
+          (*track_configs_it)->max_bitrate_bps,
+          track_configs_it - track_configs.begin()));
+    }
+    uint32_t total_available_increase = (available_bitrate - sum_min_bitrates);
+    int processed_configs = 0;
+    for (const auto& track_config_pair : max_bitrate_sorted_configs) {
+      uint32_t available_increase =
+          total_available_increase /
+          (static_cast<uint32_t>(track_configs.size() - processed_configs));
+      uint32_t consumed_increase =
+          std::min(track_configs[track_config_pair.second]->max_bitrate_bps -
+                       track_configs[track_config_pair.second]->min_bitrate_bps,
+                   available_increase);
+      track_allocations[track_config_pair.second] += consumed_increase;
+      total_available_increase -= consumed_increase;
+      ++processed_configs;
+    }
+    return track_allocations;
+  }
+}
+
+AudioPriorityBitrateAllocationStrategy::AudioPriorityBitrateAllocationStrategy(
+    std::string audio_track_id,
+    uint32_t sufficient_audio_bitrate)
+    : audio_track_id_(audio_track_id),
+      sufficient_audio_bitrate_(sufficient_audio_bitrate) {}
+
+std::vector<uint32_t> AudioPriorityBitrateAllocationStrategy::AllocateBitrates(
+    uint32_t available_bitrate,
+    const ArrayView<const TrackConfig*> track_configs) {
+  const TrackConfig* audio_track_config = NULL;
+  size_t audio_config_index = -1;
+  uint32_t sum_min_bitrates = 0;
+
+  for (auto*& track_config : track_configs) {
+    sum_min_bitrates += track_config->min_bitrate_bps;
+    if (track_config->track_id == audio_track_id_) {
+      audio_track_config = track_config;
+      audio_config_index = &track_config - &track_configs[0];
+    }
+  }
+  if (audio_track_config == NULL) {
+    return DistributeBitratesEvenly(track_configs, available_bitrate);
+  }
+  RTC_DCHECK(sufficient_audio_bitrate_ >= audio_track_config->min_bitrate_bps &&
+             sufficient_audio_bitrate_ <= audio_track_config->max_bitrate_bps);

[Taylor Brandstetter, 2017/09/11 16:55:06]

Is it possible that this DCHECK could be hit due to certain SDP being set? If so
this situation should be handled more gracefully.

[alexnarest, 2017/09/14 13:08:33]

Done.

+  if (available_bitrate <= sum_min_bitrates) {
+    return SetAllBitratesToMinimum(track_configs);
+  } else {
+    if (available_bitrate <= sum_min_bitrates + sufficient_audio_bitrate_ -
+                                 audio_track_config->min_bitrate_bps) {
+      std::vector<uint32_t> track_allocations =
+          SetAllBitratesToMinimum(track_configs);
+      track_allocations[audio_config_index] +=
+          available_bitrate - sum_min_bitrates;
+      return track_allocations;
+    } else {
+      const TrackConfig* saved_track_config = track_configs[audio_config_index];
+      TrackConfig sufficient_track_config(*track_configs[audio_config_index]);
+      sufficient_track_config.min_bitrate_bps = sufficient_audio_bitrate_;
+      track_configs[audio_config_index] = &sufficient_track_config;
+      std::vector<uint32_t> track_allocations =
+          DistributeBitratesEvenly(track_configs, available_bitrate);
+      track_configs[audio_config_index] = saved_track_config;
+      return track_allocations;
+    }
+  }
+}
+
+}  // namespace rtc