1 files changed, 246 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/video_coding/codecs/vp9/svc_config.cc b/third_party/libwebrtc/modules/video_coding/codecs/vp9/svc_config.cc
new file mode 100644
index 0000000000..7af8cab3cb
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+++ b/third_party/libwebrtc/modules/video_coding/codecs/vp9/svc_config.cc
@@ -0,0 +1,246 @@
+/*
+ *  Copyright (c) 2018 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/codecs/vp9/svc_config.h"
+
+#include <algorithm>
+#include <cmath>
+#include <memory>
+#include <vector>
+
+#include "media/base/video_common.h"
+#include "modules/video_coding/codecs/vp9/include/vp9_globals.h"
+#include "modules/video_coding/svc/create_scalability_structure.h"
+#include "modules/video_coding/svc/scalability_mode_util.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+namespace {
+const size_t kMinVp9SvcBitrateKbps = 30;
+
+const size_t kMaxNumLayersForScreenSharing = 3;
+const float kMaxScreenSharingLayerFramerateFps[] = {5.0, 10.0, 30.0};
+const size_t kMinScreenSharingLayerBitrateKbps[] = {30, 200, 500};
+const size_t kTargetScreenSharingLayerBitrateKbps[] = {150, 350, 950};
+const size_t kMaxScreenSharingLayerBitrateKbps[] = {250, 500, 950};
+
+// Gets limited number of layers for given resolution.
+size_t GetLimitedNumSpatialLayers(size_t width, size_t height) {
+  const bool is_landscape = width >= height;
+  const size_t min_width = is_landscape ? kMinVp9SpatialLayerLongSideLength
+                                        : kMinVp9SpatialLayerShortSideLength;
+  const size_t min_height = is_landscape ? kMinVp9SpatialLayerShortSideLength
+                                         : kMinVp9SpatialLayerLongSideLength;
+  const size_t num_layers_fit_horz = static_cast<size_t>(
+      std::floor(1 + std::max(0.0f, std::log2(1.0f * width / min_width))));
+  const size_t num_layers_fit_vert = static_cast<size_t>(
+      std::floor(1 + std::max(0.0f, std::log2(1.0f * height / min_height))));
+  return std::min(num_layers_fit_horz, num_layers_fit_vert);
+}
+}  // namespace
+
+std::vector<SpatialLayer> ConfigureSvcScreenSharing(size_t input_width,
+                                                    size_t input_height,
+                                                    float max_framerate_fps,
+                                                    size_t num_spatial_layers) {
+  num_spatial_layers =
+      std::min(num_spatial_layers, kMaxNumLayersForScreenSharing);
+  std::vector<SpatialLayer> spatial_layers;
+
+  for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
+    SpatialLayer spatial_layer = {0};
+    spatial_layer.width = input_width;
+    spatial_layer.height = input_height;
+    spatial_layer.maxFramerate =
+        std::min(kMaxScreenSharingLayerFramerateFps[sl_idx], max_framerate_fps);
+    spatial_layer.numberOfTemporalLayers = 1;
+    spatial_layer.minBitrate =
+        static_cast<int>(kMinScreenSharingLayerBitrateKbps[sl_idx]);
+    spatial_layer.maxBitrate =
+        static_cast<int>(kMaxScreenSharingLayerBitrateKbps[sl_idx]);
+    spatial_layer.targetBitrate =
+        static_cast<int>(kTargetScreenSharingLayerBitrateKbps[sl_idx]);
+    spatial_layer.active = true;
+    spatial_layers.push_back(spatial_layer);
+  }
+
+  return spatial_layers;
+}
+
+std::vector<SpatialLayer> ConfigureSvcNormalVideo(
+    size_t input_width,
+    size_t input_height,
+    float max_framerate_fps,
+    size_t first_active_layer,
+    size_t num_spatial_layers,
+    size_t num_temporal_layers,
+    absl::optional<ScalableVideoController::StreamLayersConfig> config) {
+  RTC_DCHECK_LT(first_active_layer, num_spatial_layers);
+
+  // Limit number of layers for given resolution.
+  size_t limited_num_spatial_layers =
+      GetLimitedNumSpatialLayers(input_width, input_height);
+  if (limited_num_spatial_layers < num_spatial_layers) {
+    RTC_LOG(LS_WARNING) << "Reducing number of spatial layers from "
+                        << num_spatial_layers << " to "
+                        << limited_num_spatial_layers
+                        << " due to low input resolution.";
+    num_spatial_layers = limited_num_spatial_layers;
+  }
+
+  // First active layer must be configured.
+  num_spatial_layers = std::max(num_spatial_layers, first_active_layer + 1);
+
+  // Ensure top layer is even enough.
+  int required_divisiblity = 1 << (num_spatial_layers - first_active_layer - 1);
+  if (config) {
+    required_divisiblity = 1;
+    for (size_t sl_idx = 0; sl_idx < num_spatial_layers; ++sl_idx) {
+      required_divisiblity = cricket::LeastCommonMultiple(
+          required_divisiblity, config->scaling_factor_den[sl_idx]);
+    }
+  }
+  input_width = input_width - input_width % required_divisiblity;
+  input_height = input_height - input_height % required_divisiblity;
+
+  std::vector<SpatialLayer> spatial_layers;
+  for (size_t sl_idx = first_active_layer; sl_idx < num_spatial_layers;
+       ++sl_idx) {
+    SpatialLayer spatial_layer = {0};
+    spatial_layer.width = input_width >> (num_spatial_layers - sl_idx - 1);
+    spatial_layer.height = input_height >> (num_spatial_layers - sl_idx - 1);
+    spatial_layer.maxFramerate = max_framerate_fps;
+    spatial_layer.numberOfTemporalLayers = num_temporal_layers;
+    spatial_layer.active = true;
+
+    if (config) {
+      spatial_layer.width = input_width * config->scaling_factor_num[sl_idx] /
+                            config->scaling_factor_den[sl_idx];
+      spatial_layer.height = input_height * config->scaling_factor_num[sl_idx] /
+                             config->scaling_factor_den[sl_idx];
+    }
+
+    // minBitrate and maxBitrate formulas were derived from
+    // subjective-quality data to determing bit rates below which video
+    // quality is unacceptable and above which additional bits do not provide
+    // benefit. The formulas express rate in units of kbps.
+
+    // TODO(ssilkin): Add to the comment PSNR/SSIM we get at encoding certain
+    // video to min/max bitrate specified by those formulas.
+    const size_t num_pixels = spatial_layer.width * spatial_layer.height;
+    int min_bitrate =
+        static_cast<int>((600. * std::sqrt(num_pixels) - 95000.) / 1000.);
+    min_bitrate = std::max(min_bitrate, 0);
+    spatial_layer.minBitrate =
+        std::max(static_cast<size_t>(min_bitrate), kMinVp9SvcBitrateKbps);
+    spatial_layer.maxBitrate =
+        static_cast<int>((1.6 * num_pixels + 50 * 1000) / 1000);
+    spatial_layer.targetBitrate =
+        (spatial_layer.minBitrate + spatial_layer.maxBitrate) / 2;
+    spatial_layers.push_back(spatial_layer);
+  }
+
+  // A workaround for situation when single HD layer is left with minBitrate
+  // about 500kbps. This would mean that there will always be at least 500kbps
+  // allocated to video regardless of how low is the actual BWE.
+  // Also, boost maxBitrate for the first layer to account for lost ability to
+  // predict from previous layers.
+  if (first_active_layer > 0) {
+    spatial_layers[0].minBitrate = kMinVp9SvcBitrateKbps;
+    // TODO(ilnik): tune this value or come up with a different formula to
+    // ensure that all singlecast configurations look good and not too much
+    // bitrate is added.
+    spatial_layers[0].maxBitrate *= 1.1;
+  }
+
+  return spatial_layers;
+}
+
+// Uses scalability mode to configure spatial layers.
+std::vector<SpatialLayer> GetVp9SvcConfig(VideoCodec& codec) {
+  RTC_DCHECK_EQ(codec.codecType, kVideoCodecVP9);
+
+  absl::optional<ScalabilityMode> scalability_mode = codec.GetScalabilityMode();
+  RTC_DCHECK(scalability_mode.has_value());
+
+  bool requested_single_spatial_layer =
+      ScalabilityModeToNumSpatialLayers(*scalability_mode) == 1;
+
+  // Limit number of spatial layers for given resolution.
+  int limited_num_spatial_layers =
+      GetLimitedNumSpatialLayers(codec.width, codec.height);
+  if (limited_num_spatial_layers <
+      ScalabilityModeToNumSpatialLayers(*scalability_mode)) {
+    ScalabilityMode limited_scalability_mode =
+        LimitNumSpatialLayers(*scalability_mode, limited_num_spatial_layers);
+    RTC_LOG(LS_WARNING)
+        << "Reducing number of spatial layers due to low input resolution: "
+        << ScalabilityModeToString(*scalability_mode) << " to "
+        << ScalabilityModeToString(limited_scalability_mode);
+    scalability_mode = limited_scalability_mode;
+    codec.SetScalabilityMode(limited_scalability_mode);
+  }
+
+  absl::optional<ScalableVideoController::StreamLayersConfig> info =
+      ScalabilityStructureConfig(*scalability_mode);
+  if (!info.has_value()) {
+    RTC_LOG(LS_WARNING) << "Failed to create structure "
+                        << ScalabilityModeToString(*scalability_mode);
+    return {};
+  }
+
+  // TODO(bugs.webrtc.org/11607): Add support for screensharing.
+  std::vector<SpatialLayer> spatial_layers =
+      GetSvcConfig(codec.width, codec.height, codec.maxFramerate,
+                   /*first_active_layer=*/0, info->num_spatial_layers,
+                   info->num_temporal_layers, /*is_screen_sharing=*/false,
+                   codec.GetScalabilityMode() ? info : absl::nullopt);
+  RTC_DCHECK(!spatial_layers.empty());
+
+  spatial_layers[0].minBitrate = kMinVp9SvcBitrateKbps;
+
+  // Use codec bitrate limits if spatial layering is not requested.
+  if (requested_single_spatial_layer) {
+    SpatialLayer& spatial_layer = spatial_layers[0];
+    spatial_layer.minBitrate = codec.minBitrate;
+    spatial_layer.maxBitrate = codec.maxBitrate;
+    spatial_layer.targetBitrate = codec.maxBitrate;
+  }
+
+  return spatial_layers;
+}
+
+std::vector<SpatialLayer> GetSvcConfig(
+    size_t input_width,
+    size_t input_height,
+    float max_framerate_fps,
+    size_t first_active_layer,
+    size_t num_spatial_layers,
+    size_t num_temporal_layers,
+    bool is_screen_sharing,
+    absl::optional<ScalableVideoController::StreamLayersConfig> config) {
+  RTC_DCHECK_GT(input_width, 0);
+  RTC_DCHECK_GT(input_height, 0);
+  RTC_DCHECK_GT(num_spatial_layers, 0);
+  RTC_DCHECK_GT(num_temporal_layers, 0);
+
+  if (is_screen_sharing) {
+    return ConfigureSvcScreenSharing(input_width, input_height,
+                                     max_framerate_fps, num_spatial_layers);
+  } else {
+    return ConfigureSvcNormalVideo(input_width, input_height, max_framerate_fps,
+                                   first_active_layer, num_spatial_layers,
+                                   num_temporal_layers, config);
+  }
+}
+
+}  // namespace webrtc