Improve the behavior when the BWE times out and when we have too little data to determine the incom…

webrtc/base/rate_statistics_unittest.cc

Index: webrtc/base/rate_statistics_unittest.cc
diff --git a/webrtc/base/rate_statistics_unittest.cc b/webrtc/base/rate_statistics_unittest.cc
index 0270253d5e2f919a99f7c627a467c5d86aaad94d..dba6a989ca2d39285a5f7fd5a7dd38ce9859fb92 100644
--- a/webrtc/base/rate_statistics_unittest.cc
+++ b/webrtc/base/rate_statistics_unittest.cc
@@ -8,6 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include <algorithm>
+
 #include "testing/gtest/include/gtest/gtest.h"
 #include "webrtc/base/rate_statistics.h"
 
@@ -26,8 +28,9 @@ TEST_F(RateStatisticsTest, TestStrictMode) {
   // Should be initialized to 0.
   EXPECT_EQ(0u, stats_.Rate(now_ms));
   stats_.Update(1500, now_ms);
-  // Expecting 24 kbps given a 500 ms window with one 1500 bytes packet.
-  EXPECT_EQ(24000u, stats_.Rate(now_ms));
+  // Expecting 1200 kbps since the window is initially kept small and grows as
+  // we have more data.
+  EXPECT_EQ(12000000u, stats_.Rate(now_ms));
   stats_.Reset();
   // Expecting 0 after init.
   EXPECT_EQ(0u, stats_.Rate(now_ms));
@@ -38,7 +41,7 @@ TEST_F(RateStatisticsTest, TestStrictMode) {
     // Approximately 1200 kbps expected. Not exact since when packets
     // are removed we will jump 10 ms to the next packet.
     if (now_ms > 0 && now_ms % 500 == 0) {
-      EXPECT_NEAR(1200000u, stats_.Rate(now_ms), 24000u);
+      EXPECT_NEAR(1200000u, stats_.Rate(now_ms), 22000u);
     }
     now_ms += 1;
   }
@@ -54,25 +57,26 @@ TEST_F(RateStatisticsTest, IncreasingThenDecreasingBitrate) {
   // Expecting 0 after init.
   uint32_t bitrate = stats_.Rate(now_ms);
   EXPECT_EQ(0u, bitrate);
+  uint32_t kExpectedBitrate = 8000000;

[perkj_webrtc, 2016/04/22 05:24:58]

nit: const uint32_t

   // 1000 bytes per millisecond until plateau is reached.
+  int prev_error = kExpectedBitrate;
   while (++now_ms < 10000) {
     stats_.Update(1000, now_ms);
-    uint32_t new_bitrate = stats_.Rate(now_ms);
-    if (new_bitrate != bitrate) {
-      // New bitrate must be higher than previous one.
-      EXPECT_GT(new_bitrate, bitrate);
-    } else {
-      // Plateau reached, 8000 kbps expected.
-      EXPECT_NEAR(8000000u, bitrate, 80000u);
-      break;
-    }
-    bitrate = new_bitrate;
+    bitrate = stats_.Rate(now_ms);
+    int error = kExpectedBitrate - bitrate;
+    error = std::abs(error);
+    // Expect the estimation error to decrease as the window is extended.
+    EXPECT_LE(error, prev_error + 1);
+    prev_error = error;
   }
+  // Window filled, expect to be close to 8000000.
+  EXPECT_EQ(8000000u, bitrate);
+
   // 1000 bytes per millisecond until 10-second mark, 8000 kbps expected.
   while (++now_ms < 10000) {
     stats_.Update(1000, now_ms);
     bitrate = stats_.Rate(now_ms);
-    EXPECT_NEAR(8000000u, bitrate, 80000u);
+    EXPECT_EQ(8000000u, bitrate);
   }
   // Zero bytes per millisecond until 0 is reached.
   while (++now_ms < 20000) {
@@ -94,4 +98,33 @@ TEST_F(RateStatisticsTest, IncreasingThenDecreasingBitrate) {
     EXPECT_EQ(0u, stats_.Rate(now_ms));
   }
 }
+
+TEST_F(RateStatisticsTest, ResetAfterSilence) {
+  int64_t now_ms = 0;
+  stats_.Reset();
+  // Expecting 0 after init.
+  uint32_t bitrate = stats_.Rate(now_ms);
+  EXPECT_EQ(0u, bitrate);
+  uint32_t kExpectedBitrate = 8000000;

[perkj_webrtc, 2016/04/22 05:24:58]

dito

+  // 1000 bytes per millisecond until the window has been filled.
+  int prev_error = kExpectedBitrate;
+  while (++now_ms < 10000) {
+    stats_.Update(1000, now_ms);
+    bitrate = stats_.Rate(now_ms);
+    int error = kExpectedBitrate - bitrate;
+    error = std::abs(error);
+    // Expect the estimation error to decrease as the window is extended.
+    EXPECT_LE(error, prev_error + 1);
+    prev_error = error;
+  }
+  // Window filled, expect to be close to 8000000.
+  EXPECT_EQ(8000000u, bitrate);
+
+  now_ms += 501;

[sprang_webrtc, 2016/04/22 10:36:58]

Can we add a named constant for the 500ms window? Looks like there are other
values that could be inferred rather than explicitly stated as well?

+  EXPECT_EQ(0u, stats_.Rate(now_ms));
+  stats_.Update(1000, now_ms);
+  // We expect one sample of 1000 bytes, and that the bitrate is measured over
+  // 2 milliseconds, i.e., 8 * 1000 / 0.002 =
+  EXPECT_EQ(8000000u, stats_.Rate(now_ms));
+}
 }  // namespace