Cast: Provide more meaningful stats.

media/cast/logging/receiver_time_offset_estimator_impl.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <algorithm>
+#include <utility>
+
+#include "base/logging.h"
+#include "media/cast/logging/receiver_time_offset_estimator_impl.h"
+
+namespace media {
+namespace cast {
+
+// This should be large enough so that we can collect all 3 events before
+// the entry gets removed from the map.
+const size_t kMaxEventTimesMapSize = 100;
+
+ReceiverTimeOffsetEstimatorImpl::ReceiverTimeOffsetEstimatorImpl()
+    : bounded_(false) {}
+
+ReceiverTimeOffsetEstimatorImpl::~ReceiverTimeOffsetEstimatorImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void ReceiverTimeOffsetEstimatorImpl::OnReceiveFrameEvent(
+    const FrameEvent& frame_event) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  CastLoggingEvent event = frame_event.type;
+  if (event != kVideoFrameEncoded && event != kVideoAckSent &&
+      event != kVideoAckReceived)
+    return;
+
+  EventTimesMap::iterator it = event_times_map_.find(frame_event.rtp_timestamp);
+  if (it == event_times_map_.end()) {
+    EventTimes event_times;
+    it = event_times_map_.insert(std::make_pair(frame_event.rtp_timestamp,
+                                                event_times)).first;
+  }
+  switch (event) {
+    case kVideoFrameEncoded:
+      // Encode is supposed to happen only once. If we see duplicate event,
+      // throw away the entry.
+      if (it->second.event_a_time.is_null()) {
+        it->second.event_a_time = frame_event.timestamp;
+      } else {
+        event_times_map_.erase(it);
+        return;
+      }
+      break;
+    case kVideoAckSent:
+      if (it->second.event_b_time.is_null()) {
+        it->second.event_b_time = frame_event.timestamp;
+      } else if (it->second.event_b_time != frame_event.timestamp) {
+        // Duplicate ack sent events are normal due to RTCP redundancy,
+        // but they must have the same event timestamp.
+        event_times_map_.erase(it);
+        return;
+      }
+      break;
+    case kVideoAckReceived:
+      // If there are duplicate ack received events, pick the one with the
+      // smallest event timestamp so we can get a better bound.
+      if (it->second.event_c_time.is_null()) {
+        it->second.event_c_time = frame_event.timestamp;
+      } else {
+        it->second.event_c_time =
+            std::min(frame_event.timestamp, it->second.event_c_time);
+      }
+      break;
+    default:
+      NOTREACHED();
+  }
+
+  if (!it->second.event_a_time.is_null() &&
+      !it->second.event_b_time.is_null() &&
+      !it->second.event_c_time.is_null()) {
+    UpdateOffsetBounds(it->second);
+    event_times_map_.erase(it);
+  }
+
+  // Keep the map size at most |kMaxEventTimesMapSize|.
+  if (event_times_map_.size() > kMaxEventTimesMapSize)
+    event_times_map_.erase(event_times_map_.begin());
+}
+
+bool ReceiverTimeOffsetEstimatorImpl::GetReceiverOffsetBounds(
+    base::TimeDelta* lower_bound,
+    base::TimeDelta* upper_bound) {
+  if (!bounded_)
+    return false;
+
+  *lower_bound = offset_lower_bound_;
+  *upper_bound = offset_upper_bound_;
+  return true;
+}
+
+void ReceiverTimeOffsetEstimatorImpl::OnReceivePacketEvent(
+    const PacketEvent& packet_event) {
+  // Not interested in packet events.
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void ReceiverTimeOffsetEstimatorImpl::UpdateOffsetBounds(
+    const EventTimes& event) {
+  base::TimeDelta lower_bound = event.event_b_time - event.event_c_time;
+  base::TimeDelta upper_bound = event.event_b_time - event.event_a_time;
+
+  if (bounded_) {
+    lower_bound = std::max(lower_bound, offset_lower_bound_);
+    upper_bound = std::min(upper_bound, offset_upper_bound_);
+  }
+
+  if (lower_bound > upper_bound) {
+    VLOG(2) << "Got bogus offset bound values [" << lower_bound.InMilliseconds()
+            << ", " << upper_bound.InMilliseconds() << "].";
+    return;
+  }
+
+  offset_lower_bound_ = lower_bound;
+  offset_upper_bound_ = upper_bound;
+  bounded_ = true;
+}
+
+}  // namespace cast
+}  // namespace media