Extract bitrate allocation of spatial/temporal layers out of codec impl.

webrtc/modules/video_coding/utility/simulcast_rate_allocator.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_rate_allocator.h"
 
 #include <algorithm>
+#include <memory>
+#include <vector>
+#include <utility>
+
+#include "webrtc/base/checks.h"
 
 namespace webrtc {
 
-webrtc::SimulcastRateAllocator::SimulcastRateAllocator(const VideoCodec& codec)
-    : codec_(codec) {}
+SimulcastRateAllocator::SimulcastRateAllocator(
+    const VideoCodec& codec,
+    std::unique_ptr<TemporalLayersFactory> tl_factory)
+    : codec_(codec), tl_factory_(std::move(tl_factory)) {
+  if (tl_factory_.get())
+    tl_factory_->SetListener(this);
+}
 
-std::vector<uint32_t> webrtc::SimulcastRateAllocator::GetAllocation(
-    uint32_t bitrate_kbps) const {
-  // 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 overridden by this.
-  const uint32_t min_bitrate_bps = codec_.numberOfSimulcastStreams == 0
-                                       ? codec_.minBitrate
-                                       : codec_.simulcastStream[0].minBitrate;
-  uint32_t left_to_allocate = std::max(min_bitrate_bps, bitrate_kbps);
-  if (codec_.maxBitrate)
-    left_to_allocate = std::min(left_to_allocate, codec_.maxBitrate);
+void SimulcastRateAllocator::OnTemporalLayersCreated(int simulcast_id,
+                                                     TemporalLayers* layers) {
+  RTC_DCHECK(temporal_layers_.find(simulcast_id) == temporal_layers_.end());
+  temporal_layers_[simulcast_id] = layers;
+}
 
-  if (codec_.numberOfSimulcastStreams < 2) {
+BitrateAllocation SimulcastRateAllocator::GetAllocation(
+    uint32_t total_bitrate_bps,
+    uint32_t framerate) {
+  uint32_t left_to_allocate = total_bitrate_bps;
+  if (codec_.maxBitrate && codec_.maxBitrate * 1000 < left_to_allocate)
+    left_to_allocate = codec_.maxBitrate * 1000;
+
+  BitrateAllocation allocated_bitrates_bps;
+  if (codec_.numberOfSimulcastStreams == 0) {
     // No simulcast, just set the target as this has been capped already.
-    return std::vector<uint32_t>(1, left_to_allocate);
+    allocated_bitrates_bps.SetBitrate(
+        0, 0, std::max(codec_.minBitrate * 1000, left_to_allocate));
+  } else {
+    // 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 overridden by this.
+    left_to_allocate =
+        std::max(codec_.simulcastStream[0].minBitrate * 1000, left_to_allocate);
+
+    // Begin by allocating bitrate to simulcast streams, putting all bitrate in
+    // temporal layer 0. We'll then distribute this stream allocation is done.

[stefan-webrtc, 2016/11/02 10:26:35]

"...distribute this when stream allocation is done"?

[sprang_webrtc, 2016/11/02 13:28:33]

For great justice!

+
+    // Allocate up to the target bitrate for each simulcast layer.
+    size_t layer = 0;
+    for (; layer < codec_.numberOfSimulcastStreams; ++layer) {
+      const SimulcastStream& stream = codec_.simulcastStream[layer];
+      if (left_to_allocate < stream.minBitrate * 1000)
+        break;
+      uint32_t allocation =
+          std::min(left_to_allocate, stream.targetBitrate * 1000);
+      allocated_bitrates_bps.SetBitrate(layer, 0, allocation);
+      left_to_allocate -= allocation;

[stefan-webrtc, 2016/11/02 10:26:35]

DCHECK to make sure left_to_allocate doesn't end up wrapping around?

[sprang_webrtc, 2016/11/02 13:28:33]

Done.

+    }
+
+    // Next, try allocate remaining bitrate, up to max bitrate, in top stream.
+    // TODO(sprang): Allocate up to max bitrate for all layers once we have a
+    //               better idea of possible performance implications.
+    if (left_to_allocate > 0) {
+      size_t active_layer = layer - 1;
+      const SimulcastStream& stream = codec_.simulcastStream[active_layer];
+      uint32_t bitrate_bps =
+          allocated_bitrates_bps.GetSpatialLayerSum(active_layer);
+      uint32_t allocation =
+          std::min(left_to_allocate, stream.maxBitrate * 1000 - bitrate_bps);
+      bitrate_bps += allocation;
+      left_to_allocate -= allocation;

[stefan-webrtc, 2016/11/02 10:26:35]

here too

[sprang_webrtc, 2016/11/02 13:28:33]

We do cap allocation to left_to_allocate two lines above, but ok :)

[stefan-webrtc, 2016/11/03 13:34:58]

I guess I missed that :)

+      allocated_bitrates_bps.SetBitrate(active_layer, 0, bitrate_bps);
+    }
   }
 
-  // Initialize bitrates with zeroes.
-  std::vector<uint32_t> allocated_bitrates_bps(codec_.numberOfSimulcastStreams,
-                                               0);
+  const int num_spatial_streams =
+      std::max(1, static_cast<int>(codec_.numberOfSimulcastStreams));
 
-  // First try to allocate up to the target bitrate for each substream.
-  size_t layer = 0;
-  for (; layer < codec_.numberOfSimulcastStreams; ++layer) {
-    const SimulcastStream& stream = codec_.simulcastStream[layer];
-    if (left_to_allocate < stream.minBitrate)
-      break;
-    uint32_t allocation = std::min(left_to_allocate, stream.targetBitrate);
-    allocated_bitrates_bps[layer] = allocation;
-    left_to_allocate -= allocation;
-  }
+  // Finally, distribute the bitrate for the simulcast streams across the
+  // available temporal layers.
+  for (int simulcast_id = 0; simulcast_id < num_spatial_streams;
+       ++simulcast_id) {
+    auto tl_it = temporal_layers_.find(simulcast_id);
+    if (tl_it == temporal_layers_.end())
+      continue;  // TODO(sprang): If > 1 SS, assume default TL alloc?

[stefan-webrtc, 2016/11/02 10:26:35]

Does this change current behavior? Seems reasonable that you can create
simulcast without temporal layers.

[sprang_webrtc, 2016/11/02 13:28:33]

This should not change the behavior, I think. 
The question I was ponder was, if no temporal layers have been configured
(rather than explicitly setting a single-layer temporal layers factory), should
we assume single layer or the default temporal layer strategy we use with
simulcast today?

[stefan-webrtc, 2016/11/03 13:34:58]

I would have expected no temporal layers...

 
-  // Next, try allocate remaining bitrate, up to max bitrate, in top layer.
-  // TODO(sprang): Allocate up to max bitrate for all layers once we have a
-  //               better idea of possible performance implications.
-  if (left_to_allocate > 0) {
-    size_t active_layer = layer - 1;
-    const SimulcastStream& stream = codec_.simulcastStream[active_layer];
-    uint32_t allocation =
-        std::min(left_to_allocate,
-                 stream.maxBitrate - allocated_bitrates_bps[active_layer]);
-    left_to_allocate -= allocation;
-    allocated_bitrates_bps[active_layer] += allocation;
+    uint32_t target_bitrate_kbps =
+        allocated_bitrates_bps.GetBitrate(simulcast_id, 0) / 1000;
+    RTC_DCHECK_EQ(
+        target_bitrate_kbps,
+        allocated_bitrates_bps.GetSpatialLayerSum(simulcast_id) / 1000);
+    uint32_t max_bitrate_kbps;
+    if (codec_.numberOfSimulcastStreams == 0) {
+      max_bitrate_kbps = codec_.maxBitrate;
+
+      // TODO(holmer): This is a temporary hack for screensharing, where we
+      // interpret the startBitrate as the encoder target bitrate. This is
+      // to allow for a different max bitrate, so if the codec can't meet
+      // the target we still allow it to overshoot up to the max before dropping
+      // frames. This hack should be improved.

[stefan-webrtc, 2016/11/02 10:26:35]

:/

[sprang_webrtc, 2016/11/02 13:28:33]

I know :(
Should be easier to get rid of after this refactoring cl though. For now I want
to make sure this is actually a 2k+ line nop....

+      if (codec_.mode == kScreensharing && codec_.targetBitrate > 0 &&
+          (codec_.codecSpecific.VP8.numberOfTemporalLayers == 2 ||
+           codec_.simulcastStream[0].numberOfTemporalLayers == 2)) {
+        int tl0_bitrate = std::min(codec_.targetBitrate, target_bitrate_kbps);
+        max_bitrate_kbps = std::min(codec_.maxBitrate, target_bitrate_kbps);
+        target_bitrate_kbps = tl0_bitrate;
+      }
+    } else {
+      max_bitrate_kbps = codec_.simulcastStream[simulcast_id].maxBitrate;
+    }
+
+    std::vector<uint32_t> tl_allocation = tl_it->second->OnRatesUpdated(
+        target_bitrate_kbps, max_bitrate_kbps, framerate);
+
+    for (size_t tl_index = 0; tl_index < tl_allocation.size(); ++tl_index) {
+      allocated_bitrates_bps.SetBitrate(simulcast_id, tl_index,
+                                        tl_allocation[tl_index] * 1000);
+    }
   }
 
   return allocated_bitrates_bps;
 }
 
-uint32_t SimulcastRateAllocator::GetPreferedBitrate() const {
-  std::vector<uint32_t> rates = GetAllocation(codec_.maxBitrate);
-  uint32_t preferred_bitrate = 0;
-  for (const uint32_t& rate : rates) {
-    preferred_bitrate += rate;
-  }
-  return preferred_bitrate;
+uint32_t SimulcastRateAllocator::GetPreferedBitrate(int frame_rate) {
+  BitrateAllocation allocation =
+      GetAllocation(codec_.maxBitrate * 1000, frame_rate);
+  return allocation.get_sum_kbps();
 }
 
 const VideoCodec& webrtc::SimulcastRateAllocator::GetCodec() const {
   return codec_;
 }
 
 }  // namespace webrtc