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_) {}
+
+  // Simulate an output bitrate for one update cycle of BitrateAdjuster.
+  void SimulateBitrate(uint32_t bitrate_in_kbit) {
+    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_in_kbit * frame_interval_ms) / 8;
+    for (size_t i = 0; i < update_frame_interval; ++i) {
+      clock_.AdvanceTimeMilliseconds(frame_interval_ms);
+      adjuster_.Update(frame_size_bytes);
+    }
+  }
+
+  void VerifyAdjustment() {
+    // The adjusted bitrate should be between the estimated bitrate and the
+    // target bitrate within clamp.
+    uint32_t target_bitrate = adjuster_.GetTargetBitrate();
+    uint32_t adjusted_bitrate = adjuster_.GetAdjustedBitrate();
+    uint32_t estimated_bitrate = adjuster_.GetEstimatedBitrate();
+    uint32_t adjusted_lower_bound = adjuster_.GetMinAdjustedBitrate();
+    uint32_t adjusted_upper_bound = adjuster_.GetMaxAdjustedBitrate();
+    EXPECT_LE(adjusted_bitrate, adjusted_upper_bound);
+    EXPECT_GE(adjusted_bitrate, adjusted_lower_bound);
+    if (estimated_bitrate > target_bitrate) {
+      EXPECT_LT(adjusted_bitrate, target_bitrate);
+    }
+  }
+
+ protected:
+  SimulatedClock clock_;
+  BitrateAdjuster adjuster_;
+};
+
+TEST_F(BitrateAdjusterTest, VaryingBitrates) {
+  const uint32_t target_bitrate = 640;
+  adjuster_.SetTargetBitrate(target_bitrate);
+
+  // Grossly overshoot for a little while. Adjusted bitrate should decrease.
+  uint32_t actual_bitrate = 2 * target_bitrate;
+  uint32_t last_adjusted_bitrate = 0;
+  uint32_t adjusted_bitrate = 0;
+
+  SimulateBitrate(actual_bitrate);
+  VerifyAdjustment();
+  last_adjusted_bitrate = adjuster_.GetAdjustedBitrate();
+
+  SimulateBitrate(actual_bitrate);
+  VerifyAdjustment();
+  adjusted_bitrate = adjuster_.GetAdjustedBitrate();
+  EXPECT_LT(adjusted_bitrate, last_adjusted_bitrate);
+  last_adjusted_bitrate = adjusted_bitrate;
+  // After two cycles we should've stabilized and hit the lower bound.
+  EXPECT_EQ(adjuster_.GetMinAdjustedBitrate(), adjusted_bitrate);
+
+  // Simulate encoder settling down. Adjusted bitrate should increase.
+  SimulateBitrate(target_bitrate);
+  adjusted_bitrate = adjuster_.GetAdjustedBitrate();
+  VerifyAdjustment();
+  EXPECT_GT(adjusted_bitrate, last_adjusted_bitrate);
+  last_adjusted_bitrate = adjusted_bitrate;
+
+  SimulateBitrate(target_bitrate);
+  adjusted_bitrate = adjuster_.GetAdjustedBitrate();
+  VerifyAdjustment();
+  EXPECT_GT(adjusted_bitrate, last_adjusted_bitrate);
+  last_adjusted_bitrate = adjusted_bitrate;
+  // After two cycles we should've stabilized and hit the upper bound.
+  EXPECT_EQ(adjuster_.GetMaxAdjustedBitrate(), adjusted_bitrate);
+}
+
+}  // namespace webrtc