Work on flexible mode and screen sharing.

webrtc/modules/video_coding/codecs/vp9/screenshare_layers.cc

+/* Copyright (c) 2015 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 <algorithm>
+#include "webrtc/modules/video_coding/codecs/vp9/screenshare_layers.h"
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+ScreenshareLayersVP9::ScreenshareLayersVP9(uint8_t num_layers) :
+    num_layers_(num_layers),
+    start_layer_(0),
+    last_timestamp_(0),
+    timestamp_initialized_(false) {
+  RTC_DCHECK_GT(num_layers, 0);
+  RTC_DCHECK_LE(num_layers, kMaxVp9NumberOfSpatialLayers);
+  memset(bits_used_, 0, sizeof(bits_used_));
+  memset(threshold_kbps_, 0, sizeof(threshold_kbps_));
+}
+
+uint8_t ScreenshareLayersVP9::GetStartLayer() const {
+  return start_layer_;
+}
+
+void ScreenshareLayersVP9::ConfigureBitrate(int threshold_kbps,
+                                            uint8_t layer_id) {
+  // The upper layer is always the layer we spill frames
+  // to when the bitrate becomes to high, therefore setting
+  // a max limit is not allowed. The top layer bitrate is
+  // never used either so configuring it makes no difference.
+  RTC_DCHECK_LT(layer_id, num_layers_ - 1);
+  threshold_kbps_[layer_id] = threshold_kbps;
+}
+
+void ScreenshareLayersVP9::LayerFrameEncoded(unsigned int size_bytes,
+                                             uint8_t layer_id) {
+  RTC_DCHECK_LT(layer_id, num_layers_);
+  bits_used_[layer_id] += size_bytes * 8;
+}
+
+VP9EncoderImpl::SuperFrameRefSettings
+ScreenshareLayersVP9::GetSuperFrameSettings(uint32_t timestamp,
+                                            bool is_keyframe) {
+  VP9EncoderImpl::SuperFrameRefSettings settings;
+  if (!timestamp_initialized_) {
+    last_timestamp_ = timestamp;
+    timestamp_initialized_ = true;
+  }
+  float time_diff = (timestamp - last_timestamp_) / 90.f;
+  float total_bits_used = 0;
+  float total_threshold_kbps = 0;
+  start_layer_ = 0;
+
+  // Up to (num_layers - 1) because we only have
+  // (num_layers - 1) thresholds to check.
+  for (int layer_id = 0; layer_id < num_layers_ - 1; ++layer_id) {
+    bits_used_[layer_id] = std::max(
+        0.f, bits_used_[layer_id] - time_diff * threshold_kbps_[layer_id]);
+    total_bits_used += bits_used_[layer_id];
+    total_threshold_kbps += threshold_kbps_[layer_id];
+
+    // If this is a keyframe then there should be no
+    // references to any previous frames.
+    if (!is_keyframe) {
+      settings.layer[layer_id].ref_buf1 = layer_id;
+      if (total_bits_used > total_threshold_kbps * 1000)
+        start_layer_ = layer_id + 1;
+    }
+
+    settings.layer[layer_id].upd_buf = layer_id;
+  }
+  // Since the above loop does not iterate over the last layer
+  // the reference of the last layer has to be set after the loop,
+  // and if this is a keyframe there should be no references to
+  // any previous frames.
+  if (!is_keyframe)
+    settings.layer[num_layers_ - 1].ref_buf1 = num_layers_ - 1;
+
+  settings.layer[num_layers_ - 1].upd_buf = num_layers_ - 1;
+  settings.is_keyframe = is_keyframe;
+  settings.start_layer = start_layer_;
+  settings.stop_layer = num_layers_ - 1;
+  last_timestamp_ = timestamp;
+  return settings;
+}
+
+}  // namespace webrtc