Selectable number of TL screenshare loopback test. Also contains some tweaks to make a single TL perform better.

BUG=

Review URL: https://codereview.webrtc.org/1242043002

Cr-Commit-Position: refs/heads/master@{#9676}

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

@@ -132,13 +132,17 @@ bool ScreenshareLayers::ConfigureBitrates(int bitrate_kbps,
   int target_bitrate_kbps = bitrate_kbps;
 
   if (cfg != nullptr) {
-    // Calculate a codec target bitrate. This may be higher than TL0, gaining
+    if (number_of_temporal_layers_ > 1) {
-    // quality at the expense of frame rate at TL0. Constraints:
+      // Calculate a codec target bitrate. This may be higher than TL0, gaining
-    // - TL0 frame rate should not be less than framerate / kMaxTL0FpsReduction.
+      // quality at the expense of frame rate at TL0. Constraints:
-    // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
+      // - TL0 frame rate no less than framerate / kMaxTL0FpsReduction.
-    target_bitrate_kbps =
+      // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
-        std::min(bitrate_kbps * kMaxTL0FpsReduction,
+      target_bitrate_kbps =
-                 max_bitrate_kbps / kAcceptableTargetOvershoot);
+          std::min(bitrate_kbps * kMaxTL0FpsReduction,
+                   max_bitrate_kbps / kAcceptableTargetOvershoot);
+
+      cfg->rc_target_bitrate = std::max(bitrate_kbps, target_bitrate_kbps);
+    }
 
     // Don't reconfigure qp limits during quality boost frames.
     if (layers_[active_layer_].state != TemporalLayer::State::kQualityBoost) {
@@ -152,8 +156,6 @@ bool ScreenshareLayers::ConfigureBitrates(int bitrate_kbps,
       layers_[0].enhanced_max_qp = min_qp_ + (((max_qp_ - min_qp_) * 80) / 100);
       layers_[1].enhanced_max_qp = min_qp_ + (((max_qp_ - min_qp_) * 85) / 100);
     }
-
-    cfg->rc_target_bitrate = std::max(bitrate_kbps, target_bitrate_kbps);
   }
 
   int avg_frame_size = (target_bitrate_kbps * 1000) / (8 * framerate);
@@ -169,6 +171,7 @@ void ScreenshareLayers::FrameEncoded(unsigned int size,
     layers_[active_layer_].state = TemporalLayer::State::kDropped;
     return;
   }
+
   if (layers_[active_layer_].state == TemporalLayer::State::kDropped) {
     layers_[active_layer_].state = TemporalLayer::State::kQualityBoost;
   }
@@ -241,7 +244,7 @@ bool ScreenshareLayers::TimeToSync(int64_t timestamp) const {
 }
 
 bool ScreenshareLayers::UpdateConfiguration(vpx_codec_enc_cfg_t* cfg) {
-  if (max_qp_ == -1)
+  if (max_qp_ == -1 || number_of_temporal_layers_ <= 1)
     return false;
 
   // If layer is in the quality boost state (following a dropped frame), update

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

@@ -112,15 +112,16 @@ TEST_F(ScreenshareLayerTest, 1Layer) {
   CodecSpecificInfoVP8 vp8_info;
   // One layer screenshare should not use the frame dropper as all frames will
   // belong to the base layer.
+  const int kSingleLayerFlags = 0;
   flags = layers_->EncodeFlags(timestamp);
-  EXPECT_EQ(0, flags);
+  EXPECT_EQ(kSingleLayerFlags, flags);
   layers_->PopulateCodecSpecific(false, &vp8_info, timestamp);
   EXPECT_EQ(static_cast<uint8_t>(kNoTemporalIdx), vp8_info.temporalIdx);
   EXPECT_FALSE(vp8_info.layerSync);
   EXPECT_EQ(kNoTl0PicIdx, vp8_info.tl0PicIdx);
   layers_->FrameEncoded(frame_size_, timestamp, kDefaultQp);
   flags = layers_->EncodeFlags(timestamp);
-  EXPECT_EQ(0, flags);
+  EXPECT_EQ(kSingleLayerFlags, flags);
   timestamp += kTimestampDelta5Fps;
   layers_->PopulateCodecSpecific(false, &vp8_info, timestamp);
   EXPECT_EQ(static_cast<uint8_t>(kNoTemporalIdx), vp8_info.temporalIdx);

webrtc/video/screenshare_loopback.cc

@@ -73,6 +73,11 @@ size_t MaxBitrate() {
   return static_cast<size_t>(FLAGS_tl1_bitrate);
 }
 
+DEFINE_int32(num_temporal_layers, 2, "Number of temporal layers to use.");
+int NumTemporalLayers() {
+  return static_cast<int>(FLAGS_num_temporal_layers);
+}
+
 DEFINE_int32(min_transmit_bitrate, 400, "Min transmit bitrate incl. padding.");
 int MinTransmitBitrate() {
   return FLAGS_min_transmit_bitrate;
@@ -128,15 +133,20 @@ DEFINE_string(
 class ScreenshareLoopback : public test::Loopback {
  public:
   explicit ScreenshareLoopback(const Config& config) : Loopback(config) {
+    CHECK_GE(config.num_temporal_layers, 1u);
+    CHECK_LE(config.num_temporal_layers, 2u);
+
     vp8_settings_ = VideoEncoder::GetDefaultVp8Settings();
     vp8_settings_.denoisingOn = false;
     vp8_settings_.frameDroppingOn = false;
-    vp8_settings_.numberOfTemporalLayers = 2;
+    vp8_settings_.numberOfTemporalLayers =
+        static_cast<unsigned char>(config.num_temporal_layers);
 
     vp9_settings_ = VideoEncoder::GetDefaultVp9Settings();
     vp9_settings_.denoisingOn = false;
     vp9_settings_.frameDroppingOn = false;
-    vp9_settings_.numberOfTemporalLayers = 2;
+    vp9_settings_.numberOfTemporalLayers =
+        static_cast<unsigned char>(config.num_temporal_layers);
   }
   virtual ~ScreenshareLoopback() {}
 
@@ -146,10 +156,13 @@ class ScreenshareLoopback : public test::Loopback {
     VideoStream* stream = &encoder_config.streams[0];
     encoder_config.content_type = VideoEncoderConfig::ContentType::kScreen;
     encoder_config.min_transmit_bitrate_bps = flags::MinTransmitBitrate();
+    int num_temporal_layers;
     if (config_.codec == "VP8") {
       encoder_config.encoder_specific_settings = &vp8_settings_;
+      num_temporal_layers = vp8_settings_.numberOfTemporalLayers;
     } else if (config_.codec == "VP9") {
       encoder_config.encoder_specific_settings = &vp9_settings_;
+      num_temporal_layers = vp9_settings_.numberOfTemporalLayers;
     } else {
       RTC_NOTREACHED() << "Codec not supported!";
       abort();
@@ -157,7 +170,10 @@ class ScreenshareLoopback : public test::Loopback {
     stream->temporal_layer_thresholds_bps.clear();
     stream->target_bitrate_bps =
         static_cast<int>(config_.start_bitrate_kbps) * 1000;
-    stream->temporal_layer_thresholds_bps.push_back(stream->target_bitrate_bps);
+    if (num_temporal_layers == 2) {
+      stream->temporal_layer_thresholds_bps.push_back(
+          stream->target_bitrate_bps);
+    }
     return encoder_config;
   }
 
@@ -202,7 +218,7 @@ void Loopback() {
                                 flags::MaxBitrate(),
                                 flags::MinTransmitBitrate(),
                                 flags::Codec(),
-                                0,  // Default number of temporal layers.
+                                flags::NumTemporalLayers(),
                                 flags::LossPercent(),
                                 flags::LinkCapacity(),
                                 flags::QueueSize(),