Extract common simulcast logic from VP8 wrapper and simulcast adapter

webrtc/modules/video_coding/utility/simulcast_state.cc

+/*
+ *  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 "webrtc/modules/video_coding/utility/simulcast_state.h"
+
+#include <algorithm>
+#include <numeric>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+SimulcastState::SimulcastState(const VideoCodec& codec) : codec_(codec) {
+  RTC_DCHECK_EQ(kVideoCodecVP8, codec_.codecType)
+      << "Only VP8 Simulcast currently supported.";
+  if (codec_.numberOfSimulcastStreams == 0) {
+    codec_.numberOfSimulcastStreams = 1;
+    codec_.simulcastStream[0] = {
+        codec_.width,
+        codec_.height,
+        codec_.codecSpecific.VP8.numberOfTemporalLayers,
+        codec_.maxBitrate,
+        codec_.targetBitrate,
+        codec_.minBitrate,
+        codec_.qpMax};
+  }
+  int start_bitrate_left = codec_.startBitrate * 1000;
+  int sum_max_bitrate = 0;
+  for (int i = 0; i < codec_.numberOfSimulcastStreams; ++i) {
+    sum_max_bitrate += codec_.simulcastStream[i].maxBitrate * 1000;
+    int target_bitrate = codec_.simulcastStream[i].targetBitrate * 1000;
+    int start_bitrate = std::min(start_bitrate_left, target_bitrate);
+    streams_.push_back(Stream(i, &codec_, start_bitrate));
+    start_bitrate_left = std::max(0, start_bitrate_left - start_bitrate);
+  }
+  if (sum_max_bitrate == 0) {
+    // All but the last stream is disabled.
+    streams_.clear();
+    streams_.push_back(Stream(0, &codec_, codec_.startBitrate * 1000));
+  }
+  AllocateBitrate(codec_.startBitrate * 1000);
+}
+
+SimulcastState::~SimulcastState() {}
+
+const std::vector<SimulcastState::Stream>& SimulcastState::Streams() const {
+  return streams_;
+}
+
+int SimulcastState::AllocateBitrate(int target_bitrate_bps) {
+  // Always allocate enough bitrate for the minimum bitrate of the first layer.
+  // Suspending below min bitrate is controlled outside the codec implementation
+  // and is not overriden by this.
+  int total_bitrate =
+      std::max(target_bitrate_bps,
+               static_cast<int>(streams_[0].config.minBitrate) * 1000);
+  int32_t bitrate_left = total_bitrate;
+
+  // Allocate min -> target bitrates as long as we have bitrate to spend.
+  int last_active_stream = 0;
+  for (auto& stream : streams_) {
+    stream.allocated_rate_bps = 0;
+    int target_bitrate =
+        std::max(stream.config.targetBitrate, stream.config.minBitrate) * 1000;
+    int allocated = IncreaseBitrateAllocation(
+        &stream, std::min(bitrate_left, target_bitrate));
+    bitrate_left -= allocated;
+    if (allocated <= 0) {
+      // Not enough bitrate for this stream, disable this and any following.
+      for (size_t i = stream.idx; i < streams_.size(); ++i) {
+        streams_[i].sending = false;
+        streams_[i].keyframe_request = false;
+        streams_[i].allocated_rate_bps = 0;
+      }
+      break;
+    }
+
+    if (allocated <= 0 || last_active_stream < stream.idx - 1) {
+      stream.sending = false;
+      stream.keyframe_request = false;
+      stream.allocated_rate_bps = 0;
+      continue;  // Continue disabling all streams above this one.
+    }
+    last_active_stream = stream.idx;
+  }
+
+  // Spend additional bits on the highest-quality active layer, up to max
+  // bitrate.
+  // TODO(pbos): Consider spending additional bits on last_active_stream-1 down
+  // to 0 and not just the top layer when we have additional bitrate to spend.
+  if (bitrate_left > 0) {
+    bitrate_left -=
+        IncreaseBitrateAllocation(&streams_[last_active_stream], bitrate_left);
+  }
+
+  total_bitrate -= bitrate_left;
+  return total_bitrate;
+}
+
+// Try to increase bitrate allocation of this stream by bitrate_kbps_delta, and
+// return how much of that budget that was allocated, if any.
+int SimulcastState::IncreaseBitrateAllocation(Stream* stream,
+                                              int bitrate_bps_delta) {
+  int new_bitrate = stream->allocated_rate_bps + bitrate_bps_delta;
+  if (new_bitrate < static_cast<int>(stream->config.minBitrate * 1000))
+    return 0;
+
+  int allocated_bitrate = bitrate_bps_delta;
+  const int max_bitrate = stream->config.maxBitrate * 1000;
+  if (max_bitrate > 0 && new_bitrate > max_bitrate) {
+    RTC_DCHECK_LE(stream->allocated_rate_bps, new_bitrate);
+    allocated_bitrate -= new_bitrate - max_bitrate;
+    new_bitrate = max_bitrate;
+  }
+
+  if (!stream->sending && new_bitrate > 0) {
+    // This stream was previously disabled, request a keyframe.
+    stream->sending = true;
+    stream->keyframe_request = true;
+  }
+  stream->allocated_rate_bps = new_bitrate;
+
+  return allocated_bitrate;
+}
+
+void SimulcastState::RequestKeyFrame(uint8_t idx) {
+  RTC_DCHECK_LT(static_cast<size_t>(idx), streams_.size());
+  streams_[idx].keyframe_request = true;
+}
+
+bool SimulcastState::GetAndResetKeyFrameRequest(uint8_t idx) {
+  RTC_DCHECK_LT(static_cast<size_t>(idx), streams_.size());
+  bool keyframe = streams_[idx].keyframe_request;
+  if (keyframe)
+    streams_[idx].keyframe_request = false;
+  return keyframe;
+}
+
+size_t SimulcastState::NumStreams() const {
+  return streams_.size();
+}
+
+size_t SimulcastState::NumSendingStreams() const {
+  size_t count = 0;
+  for (const Stream& stream : streams_) {
+    if (stream.sending)
+      ++count;
+  }
+  return count;
+}
+
+void SimulcastState::SetSending(uint8_t idx, bool sending) {
+  RTC_DCHECK(idx < streams_.size());
+  if (sending && !streams_[idx].sending)
+    streams_[idx].keyframe_request = true;
+  streams_[idx].sending = sending;
+}
+
+bool SimulcastState::IsSending(uint8_t idx) const {
+  RTC_DCHECK(idx < streams_.size());
+  return streams_[idx].sending;
+}
+
+int SimulcastState::AllocatedRate(uint8_t idx) const {
+  RTC_DCHECK(idx < streams_.size());
+  return streams_[idx].allocated_rate_bps;
+}
+
+SimulcastState::Stream::Stream(uint8_t idx, VideoCodec* codec, int start_bps)
+    : idx(idx),
+      config(codec->simulcastStream[idx]),
+      start_bitrate(
+          std::max(static_cast<int>(config.minBitrate * 1000), start_bps)),
+      parent_codec(codec),
+      sending(start_bps >= start_bitrate),
+      keyframe_request(sending),
+      allocated_rate_bps(start_bitrate) {}
+
+VideoCodec SimulcastState::Stream::AsCodec() const {
+  VideoCodec codec = *parent_codec;
+  codec.codecSpecific.VP8.numberOfTemporalLayers =
+      config.numberOfTemporalLayers;
+  codec.numberOfSimulcastStreams = 0;
+  codec.width = config.width;
+  codec.height = config.height;
+  codec.maxBitrate = config.maxBitrate;
+  codec.minBitrate = config.minBitrate;
+  codec.qpMax = config.qpMax;
+  codec.startBitrate = start_bitrate / 1000;
+  return codec;
+}
+
+}  // namespace webrtc