Break out allocation from BitrateController into a BitrateAllocator.

This also refactors some of the padding and allocation code in ViEEncoder, and
makes ChannelGroup a simple forwarder from BitrateController to
BitrateAllocator.

This CL is part of a bigger picture, see https://review.webrtc.org/35319004/ for
details.

BUG=4323
R=mflodman@webrtc.org, pbos@webrtc.org, sprang@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44399004

Cr-Commit-Position: refs/heads/master@{#8595}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8595 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/bitrate_controller/bitrate_allocator_unittest.cc b/webrtc/modules/bitrate_controller/bitrate_allocator_unittest.cc
new file mode 100644
index 0000000..f89a29d
--- /dev/null
+++ b/webrtc/modules/bitrate_controller/bitrate_allocator_unittest.cc
@@ -0,0 +1,184 @@
+/*
+ *  Copyright (c) 2012 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 <algorithm>
+#include <vector>
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/modules/bitrate_controller/include/bitrate_allocator.h"
+#include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
+
+namespace webrtc {
+
+class TestBitrateObserver : public BitrateObserver {
+ public:
+  TestBitrateObserver()
+      : last_bitrate_(0), last_fraction_loss_(0), last_rtt_(0) {}
+
+  virtual void OnNetworkChanged(uint32_t bitrate,
+                                uint8_t fraction_loss,
+                                int64_t rtt) {
+    last_bitrate_ = bitrate;
+    last_fraction_loss_ = fraction_loss;
+    last_rtt_ = rtt;
+  }
+  uint32_t last_bitrate_;
+  uint8_t last_fraction_loss_;
+  int64_t last_rtt_;
+};
+
+class BitrateAllocatorTest : public ::testing::Test {
+ protected:
+  BitrateAllocatorTest() : allocator_(new BitrateAllocator()) {}
+  ~BitrateAllocatorTest() {}
+
+  rtc::scoped_ptr<BitrateAllocator> allocator_;
+};
+
+TEST_F(BitrateAllocatorTest, UpdatingBitrateObserver) {
+  TestBitrateObserver bitrate_observer;
+  allocator_->AddBitrateObserver(&bitrate_observer, 200000, 100000, 1500000);
+  allocator_->OnNetworkChanged(200000, 0, 0);
+  EXPECT_EQ(200000u, bitrate_observer.last_bitrate_);
+
+  allocator_->AddBitrateObserver(&bitrate_observer, 1500000, 100000, 1500000);
+  allocator_->OnNetworkChanged(1500000, 0, 0);
+  EXPECT_EQ(1500000u, bitrate_observer.last_bitrate_);
+
+  allocator_->AddBitrateObserver(&bitrate_observer, 500000, 100000, 1500000);
+  allocator_->OnNetworkChanged(1500000, 0, 0);
+  EXPECT_EQ(1500000u, bitrate_observer.last_bitrate_);
+}
+
+TEST_F(BitrateAllocatorTest, TwoBitrateObserversOneRtcpObserver) {
+  TestBitrateObserver bitrate_observer_1;
+  TestBitrateObserver bitrate_observer_2;
+  allocator_->AddBitrateObserver(&bitrate_observer_1, 200000, 100000, 300000);
+  allocator_->AddBitrateObserver(&bitrate_observer_2, 200000, 200000, 300000);
+
+  // Test too low start bitrate, hence lower than sum of min. Min bitrates will
+  // be allocated to all observers.
+  allocator_->OnNetworkChanged(200000, 0, 50);
+  EXPECT_EQ(100000u, bitrate_observer_1.last_bitrate_);
+  EXPECT_EQ(0, bitrate_observer_1.last_fraction_loss_);
+  EXPECT_EQ(50, bitrate_observer_1.last_rtt_);
+  EXPECT_EQ(200000u, bitrate_observer_2.last_bitrate_);
+  EXPECT_EQ(0, bitrate_observer_2.last_fraction_loss_);
+  EXPECT_EQ(50, bitrate_observer_2.last_rtt_);
+
+  // Test a bitrate which should be distributed equally.
+  allocator_->OnNetworkChanged(500000, 0, 50);
+  const uint32_t kBitrateToShare = 500000 - 200000 - 100000;
+  EXPECT_EQ(100000u + kBitrateToShare / 2, bitrate_observer_1.last_bitrate_);
+  EXPECT_EQ(200000u + kBitrateToShare / 2, bitrate_observer_2.last_bitrate_);
+
+  // Limited by max bitrates.
+  allocator_->OnNetworkChanged(800000, 0, 50);
+  EXPECT_EQ(300000u, bitrate_observer_1.last_bitrate_);
+  EXPECT_EQ(300000u, bitrate_observer_2.last_bitrate_);
+}
+
+class BitrateAllocatorTestNoEnforceMin : public ::testing::Test {
+ protected:
+  BitrateAllocatorTestNoEnforceMin() : allocator_(new BitrateAllocator()) {
+    allocator_->EnforceMinBitrate(false);
+  }
+  ~BitrateAllocatorTestNoEnforceMin() {}
+
+  rtc::scoped_ptr<BitrateAllocator> allocator_;
+};
+
+// The following three tests verify that the EnforceMinBitrate() method works
+// as intended.
+TEST_F(BitrateAllocatorTestNoEnforceMin, OneBitrateObserver) {
+  TestBitrateObserver bitrate_observer_1;
+  allocator_->AddBitrateObserver(&bitrate_observer_1, 200000, 100000, 400000);
+
+  // High REMB.
+  allocator_->OnNetworkChanged(150000, 0, 0);
+  EXPECT_EQ(150000u, bitrate_observer_1.last_bitrate_);
+
+  // Low REMB.
+  allocator_->OnNetworkChanged(10000, 0, 0);
+  EXPECT_EQ(10000u, bitrate_observer_1.last_bitrate_);
+
+  allocator_->RemoveBitrateObserver(&bitrate_observer_1);
+}
+
+TEST_F(BitrateAllocatorTestNoEnforceMin, ThreeBitrateObservers) {
+  TestBitrateObserver bitrate_observer_1;
+  TestBitrateObserver bitrate_observer_2;
+  TestBitrateObserver bitrate_observer_3;
+  // Set up the observers with min bitrates at 100000, 200000, and 300000.
+  // Note: The start bitrate of bitrate_observer_1 (700000) is used as the
+  // overall start bitrate.
+  allocator_->AddBitrateObserver(&bitrate_observer_1, 700000, 100000, 400000);
+  allocator_->AddBitrateObserver(&bitrate_observer_2, 200000, 200000, 400000);
+  allocator_->AddBitrateObserver(&bitrate_observer_3, 200000, 300000, 400000);
+
+  // High REMB. Make sure the controllers get a fair share of the surplus
+  // (i.e., what is left after each controller gets its min rate).
+  allocator_->OnNetworkChanged(690000, 0, 0);
+  // Verify that each observer gets its min rate (sum of min rates is 600000),
+  // and that the remaining 90000 is divided equally among the three.
+  const uint32_t kBitrateToShare = 690000u - 100000u - 200000u - 300000u;
+  EXPECT_EQ(100000u + kBitrateToShare / 3, bitrate_observer_1.last_bitrate_);
+  EXPECT_EQ(200000u + kBitrateToShare / 3, bitrate_observer_2.last_bitrate_);
+  EXPECT_EQ(300000u + kBitrateToShare / 3, bitrate_observer_3.last_bitrate_);
+
+  // High REMB, but below the sum of min bitrates.
+  allocator_->OnNetworkChanged(500000, 0, 0);
+  // Verify that the first and second observers get their min bitrates, and the
+  // third gets the remainder.
+  EXPECT_EQ(100000u, bitrate_observer_1.last_bitrate_);  // Min bitrate.
+  EXPECT_EQ(200000u, bitrate_observer_2.last_bitrate_);  // Min bitrate.
+  EXPECT_EQ(200000u, bitrate_observer_3.last_bitrate_);  // Remainder.
+
+  // Low REMB.
+  allocator_->OnNetworkChanged(10000, 0, 0);
+  // Verify that the first observer gets all the rate, and the rest get zero.
+  EXPECT_EQ(10000u, bitrate_observer_1.last_bitrate_);
+  EXPECT_EQ(0u, bitrate_observer_2.last_bitrate_);
+  EXPECT_EQ(0u, bitrate_observer_3.last_bitrate_);
+
+  allocator_->RemoveBitrateObserver(&bitrate_observer_1);
+  allocator_->RemoveBitrateObserver(&bitrate_observer_2);
+  allocator_->RemoveBitrateObserver(&bitrate_observer_3);
+}
+
+TEST_F(BitrateAllocatorTestNoEnforceMin, Honors10KbpsLimit) {
+  TestBitrateObserver bitrate_observer;
+  allocator_->AddBitrateObserver(&bitrate_observer, 700000, 30000, 400000);
+
+  int min_bitrate = 0;
+  int max_bitrate = 0;
+  allocator_->GetMinMaxBitrateSumBps(&min_bitrate, &max_bitrate);
+  EXPECT_EQ(10000, min_bitrate);
+}
+
+TEST_F(BitrateAllocatorTest, ThreeBitrateObserversLowRembEnforceMin) {
+  TestBitrateObserver bitrate_observer_1;
+  TestBitrateObserver bitrate_observer_2;
+  TestBitrateObserver bitrate_observer_3;
+  allocator_->AddBitrateObserver(&bitrate_observer_1, 200000, 100000, 300000);
+  allocator_->AddBitrateObserver(&bitrate_observer_2, 200000, 200000, 300000);
+  allocator_->AddBitrateObserver(&bitrate_observer_3, 200000, 300000, 300000);
+
+  // Low REMB. Verify that all observers still get their respective min bitrate.
+  allocator_->OnNetworkChanged(1000, 0, 0);
+  EXPECT_EQ(100000u, bitrate_observer_1.last_bitrate_);  // Min cap.
+  EXPECT_EQ(200000u, bitrate_observer_2.last_bitrate_);  // Min cap.
+  EXPECT_EQ(300000u, bitrate_observer_3.last_bitrate_);  // Min cap.
+
+  allocator_->RemoveBitrateObserver(&bitrate_observer_1);
+  allocator_->RemoveBitrateObserver(&bitrate_observer_2);
+  allocator_->RemoveBitrateObserver(&bitrate_observer_3);
+}
+}  // namespace webrtc