Add experimental simulcast screen content mode

webrtc/modules/video_coding/codecs/vp8/screenshare_layers.cc

 /* Copyright (c) 2013 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/codecs/vp8/screenshare_layers.h"
@@ skipping 12 matching lines @@
 namespace webrtc {
 
 static const int kOneSecond90Khz = 90000;
 static const int kMinTimeBetweenSyncs = kOneSecond90Khz * 5;
 static const int kMaxTimeBetweenSyncs = kOneSecond90Khz * 10;
 static const int kQpDeltaThresholdForSync = 8;
 
 const double ScreenshareLayers::kMaxTL0FpsReduction = 2.5;
 const double ScreenshareLayers::kAcceptableTargetOvershoot = 2.0;
 
+constexpr int ScreenshareLayers::kMaxNumTemporalLayers;
+
 // Since this is TL0 we only allow updating and predicting from the LAST
 // reference frame.
 const int ScreenshareLayers::kTl0Flags =
     VP8_EFLAG_NO_UPD_GF | VP8_EFLAG_NO_UPD_ARF | VP8_EFLAG_NO_REF_GF |
     VP8_EFLAG_NO_REF_ARF;
 
 // Allow predicting from both TL0 and TL1.
 const int ScreenshareLayers::kTl1Flags =
     VP8_EFLAG_NO_REF_ARF | VP8_EFLAG_NO_UPD_ARF | VP8_EFLAG_NO_UPD_LAST;
 
 // Allow predicting from only TL0 to allow participants to switch to the high
 // bitrate stream. This means predicting only from the LAST reference frame, but
 // only updating GF to not corrupt TL0.
 const int ScreenshareLayers::kTl1SyncFlags =
     VP8_EFLAG_NO_REF_ARF | VP8_EFLAG_NO_REF_GF | VP8_EFLAG_NO_UPD_ARF |
     VP8_EFLAG_NO_UPD_LAST;
 
 // Always emit a frame with certain interval, even if bitrate targets have
 // been exceeded.
 const int ScreenshareLayers::kMaxFrameIntervalMs = 2000;
 
 webrtc::TemporalLayers* ScreenshareTemporalLayersFactory::Create(
     int simulcast_id,
     int num_temporal_layers,
     uint8_t initial_tl0_pic_idx) const {
-  webrtc::TemporalLayers* tl = new webrtc::ScreenshareLayers(
-      num_temporal_layers, rand(), webrtc::Clock::GetRealTimeClock());
+  webrtc::TemporalLayers* tl;
+  if (simulcast_id == 0) {
+    tl = new webrtc::ScreenshareLayers(num_temporal_layers, rand(),
+                                       webrtc::Clock::GetRealTimeClock());
+  } else {
+    RealTimeTemporalLayersFactory rt_tl_factory;
+    tl = rt_tl_factory.Create(simulcast_id, num_temporal_layers, rand());
+  }
   if (listener_)
     listener_->OnTemporalLayersCreated(simulcast_id, tl);
   return tl;
 }
 
 ScreenshareLayers::ScreenshareLayers(int num_temporal_layers,
                                      uint8_t initial_tl0_pic_idx,
                                      Clock* clock)
     : clock_(clock),
-      number_of_temporal_layers_(num_temporal_layers),
+      number_of_temporal_layers_(
+          std::min(kMaxNumTemporalLayers, num_temporal_layers)),
       last_base_layer_sync_(false),
       tl0_pic_idx_(initial_tl0_pic_idx),
       active_layer_(-1),
       last_timestamp_(-1),
       last_sync_timestamp_(-1),
       last_emitted_tl0_timestamp_(-1),
       min_qp_(-1),
       max_qp_(-1),
       max_debt_bytes_(0),
       encode_framerate_(1000.0f, 1000.0f),  // 1 second window, second scale.
       bitrate_updated_(false) {
-  RTC_CHECK_GT(num_temporal_layers, 0);
-  RTC_CHECK_LE(num_temporal_layers, 2);
+  RTC_CHECK_GT(number_of_temporal_layers_, 0);
+  RTC_CHECK_LE(number_of_temporal_layers_, kMaxNumTemporalLayers);
 }
 
 ScreenshareLayers::~ScreenshareLayers() {
   UpdateHistograms();
 }
 
 int ScreenshareLayers::CurrentLayerId() const {
   // Codec does not use temporal layers for screenshare.
   return 0;
 }
@@ skipping 314 matching lines @@
       RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.Screenshare.Layer1.Qp",
                                  stats_.tl1_qp_sum_ / stats_.num_tl1_frames_);
       RTC_HISTOGRAM_COUNTS_10000(
           "WebRTC.Video.Screenshare.Layer1.TargetBitrate",
           stats_.tl1_target_bitrate_sum_ / stats_.num_tl1_frames_);
     }
   }
 }
 
 }  // namespace webrtc