Improve probing by ignoring small packets which otherwise break the mechanism. These small packets are common for H.264 where the first packet of an IDR contains the parameter sets. BUG=4806 Review URL: https://codereview.webrtc.org/1221943002 Cr-Commit-Position: refs/heads/master@{#9639}

diff --git a/webrtc/modules/pacing/bitrate_prober.cc b/webrtc/modules/pacing/bitrate_prober.cc
index 1ed6298..bedb892 100644
--- a/webrtc/modules/pacing/bitrate_prober.cc
+++ b/webrtc/modules/pacing/bitrate_prober.cc

@@ -29,6 +29,8 @@
 }
 }  // namespace
 
+const size_t BitrateProber::kMinProbePacketSize = 200;
+
 BitrateProber::BitrateProber()
     : probing_state_(kDisabled),
       packet_size_last_send_(0),
@@ -88,7 +90,8 @@
   // We will send the first probe packet immediately if no packet has been
   // sent before.
   int time_until_probe_ms = 0;
-  if (packet_size_last_send_ > 0 && probing_state_ == kProbing) {
+  if (packet_size_last_send_ > kMinProbePacketSize &&
+      probing_state_ == kProbing) {
     int next_delta_ms = ComputeDeltaFromBitrate(packet_size_last_send_,
                                                 probe_bitrates_.front());
     time_until_probe_ms = next_delta_ms - elapsed_time_ms;

diff --git a/webrtc/modules/pacing/bitrate_prober.h b/webrtc/modules/pacing/bitrate_prober.h
index b3f52af..c26b0d6 100644
--- a/webrtc/modules/pacing/bitrate_prober.h
+++ b/webrtc/modules/pacing/bitrate_prober.h

@@ -22,6 +22,8 @@
 // on being protected by the caller.
 class BitrateProber {
  public:
+  static const size_t kMinProbePacketSize;
+
   BitrateProber();
 
   void SetEnabled(bool enable);

diff --git a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
index e83ac81..c5faf16 100644
--- a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
+++ b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc

@@ -16,6 +16,7 @@
 #include "webrtc/base/scoped_ptr.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
+#include "webrtc/modules/pacing/bitrate_prober.h"
 #include "webrtc/system_wrappers/interface/clock.h"
 #include "webrtc/system_wrappers/interface/critical_section_wrapper.h"
 #include "webrtc/system_wrappers/interface/logging.h"
@@ -268,7 +269,10 @@
   uint32_t ts_delta = 0;
   int64_t t_delta = 0;
   int size_delta = 0;
-  // For now only try to detect probes while we don't have a valid estimate.
+  // For now only try to detect probes while we don't have a valid estimate, and
+  // make sure the packet was paced. We currently assume that only packets
+  // larger than 200 bytes are paced by the sender.
+  was_paced = was_paced && payload_size > BitrateProber::kMinProbePacketSize;
   if (was_paced &&
       (!remote_rate_.ValidEstimate() ||
        now_ms - first_packet_time_ms_ < kInitialProbingIntervalMs)) {

diff --git a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time_unittest.cc b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time_unittest.cc
index 6f8d6cb..c2137d8 100644
--- a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time_unittest.cc
+++ b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time_unittest.cc

@@ -38,7 +38,7 @@
 }
 
 TEST_F(RemoteBitrateEstimatorAbsSendTimeTest, RateIncreaseRtpTimestamps) {
-  RateIncreaseRtpTimestampsTestHelper(1089);
+  RateIncreaseRtpTimestampsTestHelper(1240);
 }
 
 TEST_F(RemoteBitrateEstimatorAbsSendTimeTest, CapacityDropOneStream) {
@@ -259,4 +259,36 @@
   EXPECT_TRUE(bitrate_observer_->updated());
   EXPECT_NEAR(bitrate_observer_->latest_bitrate(), 4000000u, 10000);
 }
+
+TEST_F(RemoteBitrateEstimatorAbsSendTimeTest, ProbingIgnoresSmallPackets) {
+  const int kProbeLength = 5;
+  int64_t now_ms = clock_.TimeInMilliseconds();
+  // Probing with 200 bytes every 10 ms, should be ignored by the probe
+  // detection.
+  for (int i = 0; i < kProbeLength; ++i) {
+    clock_.AdvanceTimeMilliseconds(10);
+    now_ms = clock_.TimeInMilliseconds();
+    IncomingPacket(0, 200, now_ms, 90 * now_ms, AbsSendTime(now_ms, 1000),
+                   true);
+  }
+
+  EXPECT_EQ(0, bitrate_estimator_->Process());
+  EXPECT_FALSE(bitrate_observer_->updated());
+
+  // Followed by a probe with 1000 bytes packets, should be detected as a
+  // probe.
+  for (int i = 0; i < kProbeLength; ++i) {
+    clock_.AdvanceTimeMilliseconds(10);
+    now_ms = clock_.TimeInMilliseconds();
+    IncomingPacket(0, 1000, now_ms, 90 * now_ms, AbsSendTime(now_ms, 1000),
+                   true);
+  }
+
+  // Wait long enough so that we can call Process again.
+  clock_.AdvanceTimeMilliseconds(1000);
+
+  EXPECT_EQ(0, bitrate_estimator_->Process());
+  EXPECT_TRUE(bitrate_observer_->updated());
+  EXPECT_NEAR(bitrate_observer_->latest_bitrate(), 800000u, 10000);
+}
 }  // namespace webrtc