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/*
* 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
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