1 files changed, 115 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/video_coding/timing/frame_delay_variation_kalman_filter_unittest.cc b/third_party/libwebrtc/modules/video_coding/timing/frame_delay_variation_kalman_filter_unittest.cc
new file mode 100644
index 0000000000..6103f3a1bc
--- /dev/null
+++ b/third_party/libwebrtc/modules/video_coding/timing/frame_delay_variation_kalman_filter_unittest.cc
@@ -0,0 +1,115 @@
+/*
+ *  Copyright (c) 2022 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/timing/frame_delay_variation_kalman_filter.h"
+
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+// This test verifies that the initial filter state (link bandwidth, link
+// propagation delay) is such that a frame of size zero would take no time to
+// propagate.
+TEST(FrameDelayVariationKalmanFilterTest,
+     InitializedFilterWithZeroSizeFrameTakesNoTimeToPropagate) {
+  FrameDelayVariationKalmanFilter filter;
+
+  // A zero-sized frame...
+  double frame_size_variation_bytes = 0.0;
+
+  // ...should take no time to propagate due to it's size...
+  EXPECT_EQ(filter.GetFrameDelayVariationEstimateSizeBased(
+                frame_size_variation_bytes),
+            0.0);
+
+  // ...and no time due to the initial link propagation delay being zero.
+  EXPECT_EQ(
+      filter.GetFrameDelayVariationEstimateTotal(frame_size_variation_bytes),
+      0.0);
+}
+
+// TODO(brandtr): Look into if there is a factor 1000 missing here? It seems
+// unreasonable to have an initial link bandwidth of 512 _mega_bits per second?
+TEST(FrameDelayVariationKalmanFilterTest,
+     InitializedFilterWithSmallSizeFrameTakesFixedTimeToPropagate) {
+  FrameDelayVariationKalmanFilter filter;
+
+  // A 1000-byte frame...
+  double frame_size_variation_bytes = 1000.0;
+  // ...should take around `1000.0 / (512e3 / 8.0) = 0.015625 ms` to transmit.
+  double expected_frame_delay_variation_estimate_ms = 1000.0 / (512e3 / 8.0);
+
+  EXPECT_EQ(filter.GetFrameDelayVariationEstimateSizeBased(
+                frame_size_variation_bytes),
+            expected_frame_delay_variation_estimate_ms);
+  EXPECT_EQ(
+      filter.GetFrameDelayVariationEstimateTotal(frame_size_variation_bytes),
+      expected_frame_delay_variation_estimate_ms);
+}
+
+TEST(FrameDelayVariationKalmanFilterTest,
+     NegativeNoiseVarianceDoesNotUpdateFilter) {
+  FrameDelayVariationKalmanFilter filter;
+
+  // Negative variance...
+  double var_noise = -0.1;
+  filter.PredictAndUpdate(/*frame_delay_variation_ms=*/3,
+                          /*frame_size_variation_bytes=*/200.0,
+                          /*max_frame_size_bytes=*/2000, var_noise);
+
+  // ...does _not_ update the filter.
+  EXPECT_EQ(filter.GetFrameDelayVariationEstimateTotal(
+                /*frame_size_variation_bytes=*/0.0),
+            0.0);
+
+  // Positive variance...
+  var_noise = 0.1;
+  filter.PredictAndUpdate(/*frame_delay_variation_ms=*/3,
+                          /*frame_size_variation_bytes=*/200.0,
+                          /*max_frame_size_bytes=*/2000, var_noise);
+
+  // ...does update the filter.
+  EXPECT_GT(filter.GetFrameDelayVariationEstimateTotal(
+                /*frame_size_variation_bytes=*/0.0),
+            0.0);
+}
+
+TEST(FrameDelayVariationKalmanFilterTest,
+     VerifyConvergenceWithAlternatingDeviations) {
+  FrameDelayVariationKalmanFilter filter;
+
+  // One frame every 33 ms.
+  int framerate_fps = 30;
+  // Let's assume approximately 10% delay variation.
+  double frame_delay_variation_ms = 3;
+  // With a bitrate of 512 kbps, each frame will be around 2000 bytes.
+  double max_frame_size_bytes = 2000;
+  // And again, let's assume 10% size deviation.
+  double frame_size_variation_bytes = 200;
+  double var_noise = 0.1;
+  int test_duration_s = 60;
+
+  for (int i = 0; i < test_duration_s * framerate_fps; ++i) {
+    // For simplicity, assume alternating variations.
+    double sign = (i % 2 == 0) ? 1.0 : -1.0;
+    filter.PredictAndUpdate(sign * frame_delay_variation_ms,
+                            sign * frame_size_variation_bytes,
+                            max_frame_size_bytes, var_noise);
+  }
+
+  // Verify that the filter has converged within a margin of 0.1 ms.
+  EXPECT_NEAR(
+      filter.GetFrameDelayVariationEstimateTotal(frame_size_variation_bytes),
+      frame_delay_variation_ms, 0.1);
+}
+
+}  // namespace
+}  // namespace webrtc