Selectable number of TL screenshare loopback test

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 49 matching lines @@
 }
 
 int ScreenshareLayers::CurrentLayerId() const {
   // Codec does not use temporal layers for screenshare.
   return 0;
 }
 
 int ScreenshareLayers::EncodeFlags(uint32_t timestamp) {
   if (number_of_temporal_layers_ <= 1) {
     // No flags needed for 1 layer screenshare.
-    return 0;
+    return kTl0Flags;

[stefan-webrtc, 2015/08/04 14:40:28]

What does this change mean? That we constrain the stream to not use all
reference buffers if doing 1 layer screenshare? That seems bad to me.

[sprang_webrtc, 2015/08/04 14:56:06]

Yes. This was a hack I did to get overshoot detection to work, but that should
be solved in libvpx instead. Reverted.

   }
 
   int64_t unwrapped_timestamp = time_wrap_handler_.Unwrap(timestamp);
   int flags = 0;
 
   if (active_layer_ == -1 ||
       layers_[active_layer_].state != TemporalLayer::State::kDropped) {
     if (layers_[0].debt_bytes_ > max_debt_bytes_) {
       // Must drop TL0, encode TL1 instead.
       if (layers_[1].debt_bytes_ > max_debt_bytes_) {
@@ skipping 44 matching lines @@
 bool ScreenshareLayers::ConfigureBitrates(int bitrate_kbps,
                                           int max_bitrate_kbps,
                                           int framerate,
                                           vpx_codec_enc_cfg_t* cfg) {
   layers_[0].target_rate_kbps_ = bitrate_kbps;
   layers_[1].target_rate_kbps_ = max_bitrate_kbps;
 
   int target_bitrate_kbps = bitrate_kbps;
 
   if (cfg != nullptr) {
-    // Calculate a codec target bitrate. This may be higher than TL0, gaining
-    // quality at the expense of frame rate at TL0. Constraints:
-    // - TL0 frame rate should not be less than framerate / kMaxTL0FpsReduction.
-    // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
-    target_bitrate_kbps =
-        std::min(bitrate_kbps * kMaxTL0FpsReduction,
-                 max_bitrate_kbps / kAcceptableTargetOvershoot);
+    if (number_of_temporal_layers_ > 1) {
+      // Calculate a codec target bitrate. This may be higher than TL0, gaining
+      // quality at the expense of frame rate at TL0. Constraints:
+      // - TL0 frame rate no less than framerate / kMaxTL0FpsReduction.
+      // - Target rate * kAcceptableTargetOvershoot should not exceed TL1 rate.
+      target_bitrate_kbps =
+          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) {
       min_qp_ = cfg->rc_min_quantizer;
       max_qp_ = cfg->rc_max_quantizer;
       // After a dropped frame, a frame with max qp will be encoded and the
       // quality will then ramp up from there. To boost the speed of recovery,
       // encode the next frame with lower max qp. TL0 is the most important to
       // improve since the errors in this layer will propagate to TL1.
       // Currently, reduce max qp by 20% for TL0 and 15% for TL1.
       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);
   max_debt_bytes_ = 4 * avg_frame_size;
 
   return true;
 }
 
 void ScreenshareLayers::FrameEncoded(unsigned int size,
                                      uint32_t timestamp,
                                      int qp) {
   if (size == 0) {
     layers_[active_layer_].state = TemporalLayer::State::kDropped;
     return;
   }
+
   if (layers_[active_layer_].state == TemporalLayer::State::kDropped) {
     layers_[active_layer_].state = TemporalLayer::State::kQualityBoost;
   }
 
   if (qp != -1)
     layers_[active_layer_].last_qp = qp;
 
   if (active_layer_ == 0) {
     layers_[0].debt_bytes_ += size;
     layers_[1].debt_bytes_ += size;
@@ skipping 52 matching lines @@
     return false;
   }
   // Issue a sync frame if difference in quality between TL0 and TL1 isn't too
   // large.
   if (layers_[0].last_qp - layers_[1].last_qp < kQpDeltaThresholdForSync)
     return true;
   return false;
 }
 
 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
   // the configuration with the adjusted (lower) qp and set the state back to
   // normal.
   unsigned int adjusted_max_qp;
   if (layers_[active_layer_].state == TemporalLayer::State::kQualityBoost &&
       layers_[active_layer_].enhanced_max_qp != -1) {
     adjusted_max_qp = layers_[active_layer_].enhanced_max_qp;
     layers_[active_layer_].state = TemporalLayer::State::kNormal;
@@ skipping 13 matching lines @@
 void ScreenshareLayers::TemporalLayer::UpdateDebt(int64_t delta_ms) {
   uint32_t debt_reduction_bytes = target_rate_kbps_ * delta_ms / 8;
   if (debt_reduction_bytes >= debt_bytes_) {
     debt_bytes_ = 0;
   } else {
     debt_bytes_ -= debt_reduction_bytes;
   }
 }
 
 }  // namespace webrtc