Frame dropper improvements & cleanup

webrtc/modules/video_coding/utility/frame_dropper_unittest.cc

+/*
+ *  Copyright (c) 2016 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/utility/frame_dropper.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/base/logging.h"
+
+namespace webrtc {
+
+namespace {
+
+const float kTargetBitRateKbps = 300;
+const float kIncomingFrameRate = 30;
+const size_t kFrameSizeBytes = 1250;
+
+const size_t kLargeFrameSizeBytes = 25000;
+
+const bool kIncludeKeyFrame = true;
+const bool kDoNotIncludeKeyFrame = false;
+
+}  // namespace
+
+class FrameDropperTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    frame_dropper_.SetRates(kTargetBitRateKbps, kIncomingFrameRate);
+  }
+
+  void OverflowLeakyBucket() {
+    // Overflow bucket in frame dropper.
+    for (int i = 0; i < kIncomingFrameRate; ++i) {
+      frame_dropper_.Fill(kFrameSizeBytes, true);
+    }
+    frame_dropper_.Leak(kIncomingFrameRate);
+  }
+
+  void ValidateNoDropsAtTargetBitrate(int large_frame_size_bytes,
+                                      int large_frame_rate,
+                                      bool is_large_frame_delta) {
+    // Smaller frame size is computed to meet |kTargetBitRateKbps|.
+    int small_frame_size_bytes =
+        kFrameSizeBytes -
+        (large_frame_size_bytes * large_frame_rate) / kIncomingFrameRate;
+
+    for (int i = 1; i <= 5 * large_frame_rate; ++i) {
+      // Large frame. First frame is always a key frame.
+      frame_dropper_.Fill(large_frame_size_bytes,
+                          (i == 1) ? false : is_large_frame_delta);
+      frame_dropper_.Leak(kIncomingFrameRate);
+      EXPECT_FALSE(frame_dropper_.DropFrame());
+
+      // Smaller frames.
+      for (int j = 1; j < kIncomingFrameRate / large_frame_rate; ++j) {
+        frame_dropper_.Fill(small_frame_size_bytes, true);
+        frame_dropper_.Leak(kIncomingFrameRate);
+        EXPECT_FALSE(frame_dropper_.DropFrame());
+      }
+    }
+  }
+
+  void ValidateThroughputMatchesTargetBitrate(int bitrate_kbps,
+                                              bool include_keyframe) {
+    int delta_frame_size;
+    int total_bytes = 0;
+
+    if (include_keyframe) {
+      delta_frame_size = ((1000.0 / 8 * bitrate_kbps) - kLargeFrameSizeBytes) /
+                         (kIncomingFrameRate - 1);
+    } else {
+      delta_frame_size = bitrate_kbps * 1000.0 / (8 * kIncomingFrameRate);
+    }
+    const int kNumIterations = 1000;
+    for (int i = 1; i <= kNumIterations; ++i) {
+      int j = 0;
+      if (include_keyframe) {
+        if (!frame_dropper_.DropFrame()) {
+          frame_dropper_.Fill(kLargeFrameSizeBytes, false);
+          total_bytes += kLargeFrameSizeBytes;
+        }
+        frame_dropper_.Leak(kIncomingFrameRate);
+        j++;
+      }
+      for (; j < kIncomingFrameRate; ++j) {
+        if (!frame_dropper_.DropFrame()) {
+          frame_dropper_.Fill(delta_frame_size, true);
+          total_bytes += delta_frame_size;
+        }
+        frame_dropper_.Leak(kIncomingFrameRate);
+      }
+    }
+    float throughput_kbps = total_bytes * 8.0 / (1000 * kNumIterations);
+    float deviation_from_target =
+        (throughput_kbps - kTargetBitRateKbps) * 100.0 / kTargetBitRateKbps;
+    if (deviation_from_target < 0) {
+      deviation_from_target = -deviation_from_target;
+    }
+
+    // Variation is < 0.1%
+    EXPECT_LE(deviation_from_target, 0.1);
+  }
+
+  FrameDropper frame_dropper_;
+};
+
+TEST_F(FrameDropperTest, NoDropsWhenDisabled) {
+  frame_dropper_.Enable(false);
+  OverflowLeakyBucket();
+  EXPECT_FALSE(frame_dropper_.DropFrame());
+}
+
+TEST_F(FrameDropperTest, DropsByDefaultWhenBucketOverflows) {
+  OverflowLeakyBucket();
+  EXPECT_TRUE(frame_dropper_.DropFrame());
+}
+
+TEST_F(FrameDropperTest, NoDropsWhenFillRateMatchesLeakRate) {
+  for (int i = 0; i < 5 * kIncomingFrameRate; ++i) {
+    frame_dropper_.Fill(kFrameSizeBytes, true);
+    frame_dropper_.Leak(kIncomingFrameRate);
+    EXPECT_FALSE(frame_dropper_.DropFrame());
+  }
+}
+
+TEST_F(FrameDropperTest, LargeKeyFrames) {
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes, 1, false);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 2, 2, false);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 4, 4, false);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 8, 8, false);
+}
+
+TEST_F(FrameDropperTest, LargeDeltaFrames) {
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes, 1, true);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 2, 2, true);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 4, 4, true);
+  frame_dropper_.Reset();
+  ValidateNoDropsAtTargetBitrate(kLargeFrameSizeBytes / 8, 8, true);
+}
+
+TEST_F(FrameDropperTest, TrafficVolumeAboveAvailableBandwidth) {
+  ValidateThroughputMatchesTargetBitrate(700, kIncludeKeyFrame);
+  ValidateThroughputMatchesTargetBitrate(700, kDoNotIncludeKeyFrame);
+  ValidateThroughputMatchesTargetBitrate(600, kIncludeKeyFrame);
+  ValidateThroughputMatchesTargetBitrate(600, kDoNotIncludeKeyFrame);
+  ValidateThroughputMatchesTargetBitrate(500, kIncludeKeyFrame);
+  ValidateThroughputMatchesTargetBitrate(500, kDoNotIncludeKeyFrame);
+}
+
+}  // namespace webrtc