Bitrate controller for VideoToolbox encoder.

webrtc/modules/video_coding/bitrate_adjuster_unittest.cc

+/*
+ *  Copyright 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 "testing/gtest/include/gtest/gtest.h"
+
+#include "webrtc/modules/video_coding/include/bitrate_adjuster.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+class BitrateAdjusterTest : public ::testing::Test {
+ public:
+  BitrateAdjusterTest()
+      : clock_(0),
+        adjuster_(&clock_, kMinAdjustedBitratePct, kMaxAdjustedBitratePct) {}
+
+  // Simulate an output bitrate for one update cycle of BitrateAdjuster.
+  void SimulateBitrateBps(uint32_t bitrate_bps) {
+    const uint32_t update_interval_ms =
+        BitrateAdjuster::kBitrateUpdateIntervalMs;
+    const uint32_t update_frame_interval =
+        BitrateAdjuster::kBitrateUpdateFrameInterval;
+    // Round up frame interval so we get one cycle passes.
+    const uint32_t frame_interval_ms =
+        (update_interval_ms + update_frame_interval - 1) /
+        update_frame_interval;
+    const size_t frame_size_bytes =
+        (bitrate_bps * frame_interval_ms) / (8 * 1000);
+    for (size_t i = 0; i < update_frame_interval; ++i) {
+      clock_.AdvanceTimeMilliseconds(frame_interval_ms);
+      adjuster_.Update(frame_size_bytes);
+    }
+  }
+
+  uint32_t GetTargetBitrateBpsPct(float pct) {
+    return pct * adjuster_.GetTargetBitrateBps();
+  }
+
+  void VerifyAdjustment() {
+    // The adjusted bitrate should be between the estimated bitrate and the
+    // target bitrate within clamp.
+    uint32_t target_bitrate_bps = adjuster_.GetTargetBitrateBps();
+    uint32_t adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
+    uint32_t estimated_bitrate_bps = adjuster_.GetEstimatedBitrateBps();
+    uint32_t adjusted_lower_bound_bps =
+        GetTargetBitrateBpsPct(kMinAdjustedBitratePct);
+    uint32_t adjusted_upper_bound_bps =
+        GetTargetBitrateBpsPct(kMaxAdjustedBitratePct);
+    EXPECT_LE(adjusted_bitrate_bps, adjusted_upper_bound_bps);
+    EXPECT_GE(adjusted_bitrate_bps, adjusted_lower_bound_bps);
+    if (estimated_bitrate_bps > target_bitrate_bps) {
+      EXPECT_LT(adjusted_bitrate_bps, target_bitrate_bps);
+    }
+  }
+
+ protected:
+  static const float kMinAdjustedBitratePct;
+  static const float kMaxAdjustedBitratePct;
+  SimulatedClock clock_;
+  BitrateAdjuster adjuster_;
+};
+
+const float BitrateAdjusterTest::kMinAdjustedBitratePct = .5f;
+const float BitrateAdjusterTest::kMaxAdjustedBitratePct = .95f;
+
+TEST_F(BitrateAdjusterTest, VaryingBitrates) {
+  const uint32_t target_bitrate_bps = 640000;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+
+  // Grossly overshoot for a little while. Adjusted bitrate should decrease.
+  uint32_t actual_bitrate_bps = 2 * target_bitrate_bps;
+  uint32_t last_adjusted_bitrate_bps = 0;
+  uint32_t adjusted_bitrate_bps = 0;
+
+  SimulateBitrateBps(actual_bitrate_bps);
+  VerifyAdjustment();
+  last_adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
+
+  SimulateBitrateBps(actual_bitrate_bps);
+  VerifyAdjustment();
+  adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
+  EXPECT_LT(adjusted_bitrate_bps, last_adjusted_bitrate_bps);
+  last_adjusted_bitrate_bps = adjusted_bitrate_bps;
+  // After two cycles we should've stabilized and hit the lower bound.
+  EXPECT_EQ(GetTargetBitrateBpsPct(kMinAdjustedBitratePct),
+            adjusted_bitrate_bps);
+
+  // Simulate encoder settling down. Adjusted bitrate should increase.
+  SimulateBitrateBps(target_bitrate_bps);
+  adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
+  VerifyAdjustment();
+  EXPECT_GT(adjusted_bitrate_bps, last_adjusted_bitrate_bps);
+  last_adjusted_bitrate_bps = adjusted_bitrate_bps;
+
+  SimulateBitrateBps(target_bitrate_bps);
+  adjusted_bitrate_bps = adjuster_.GetAdjustedBitrateBps();
+  VerifyAdjustment();
+  EXPECT_GT(adjusted_bitrate_bps, last_adjusted_bitrate_bps);
+  last_adjusted_bitrate_bps = adjusted_bitrate_bps;
+  // After two cycles we should've stabilized and hit the upper bound.
+  EXPECT_EQ(GetTargetBitrateBpsPct(kMaxAdjustedBitratePct),
+            adjusted_bitrate_bps);
+}
+
+// Tests that large changes in target bitrate will result in immediate change
+// in adjusted bitrate.
+TEST_F(BitrateAdjusterTest, LargeTargetDelta) {
+  uint32_t target_bitrate_bps = 640000;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  float delta_pct = BitrateAdjuster::kBitrateTolerancePct * 2;
+
+  target_bitrate_bps = (1 + delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  target_bitrate_bps = (1 - delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+}
+
+// Tests that small changes in target bitrate within tolerance will not affect
+// adjusted bitrate immediately.
+TEST_F(BitrateAdjusterTest, SmallTargetDelta) {
+  const uint32_t initial_target_bitrate_bps = 640000;
+  uint32_t target_bitrate_bps = initial_target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  float delta_pct = BitrateAdjuster::kBitrateTolerancePct / 2;
+
+  target_bitrate_bps = (1 + delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  target_bitrate_bps = (1 - delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+}
+
+TEST_F(BitrateAdjusterTest, SmallTargetDeltaOverflow) {
+  const uint32_t initial_target_bitrate_bps = 640000;
+  uint32_t target_bitrate_bps = initial_target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  float delta_pct = BitrateAdjuster::kBitrateTolerancePct / 2;
+
+  target_bitrate_bps = (1 + delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(initial_target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+
+  // 1.05 * 1.05 is 1.1 which is greater than tolerance for the initial target
+  // bitrate. Since we didn't advance the clock the adjuster never updated.
+  target_bitrate_bps = (1 + delta_pct) * target_bitrate_bps;
+  adjuster_.SetTargetBitrateBps(target_bitrate_bps);
+  EXPECT_EQ(target_bitrate_bps, adjuster_.GetAdjustedBitrateBps());
+}
+
+}  // namespace webrtc