Bug 1127646 - Report MSE Join Latency and MTBR in telemetry - r=cpearce,bsmedberg

dom/html/HTMLMediaElement.cpp

@@ -1219,6 +1219,9 @@ nsresult HTMLMediaElement::LoadResource()
     mMediaSource = source.forget();
     nsRefPtr<MediaResource> resource =
       MediaSourceDecoder::CreateResource(mMediaSource->GetPrincipal());
+    if (IsAutoplayEnabled()) {
+      mJoinLatency.Start();
+    }
     return FinishDecoderSetup(decoder, resource, nullptr, nullptr);
   }
 
@@ -2585,6 +2588,17 @@ HTMLMediaElement::ReportMSETelemetry()
 
   Telemetry::Accumulate(Telemetry::VIDEO_MSE_UNLOAD_STATE, state);
   LOG(PR_LOG_DEBUG, ("%p VIDEO_MSE_UNLOAD_STATE = %d", this, state));
+
+  Telemetry::Accumulate(Telemetry::VIDEO_MSE_PLAY_TIME_MS, SECONDS_TO_MS(mPlayTime.Total()));
+  LOG(PR_LOG_DEBUG, ("%p VIDEO_MSE_PLAY_TIME_MS = %f", this, mPlayTime.Total()));
+
+  Telemetry::Accumulate(Telemetry::VIDEO_MSE_BUFFERING_COUNT, mRebufferTime.Count());
+  LOG(PR_LOG_DEBUG, ("%p VIDEO_MSE_BUFFERING_COUNT = %d", this, mRebufferTime.Count()));
+
+  double latency = mJoinLatency.Count() ? mJoinLatency.Total() / mJoinLatency.Count() : 0.0;
+  Telemetry::Accumulate(Telemetry::VIDEO_MSE_JOIN_LATENCY_MS, SECONDS_TO_MS(latency));
+  LOG(PR_LOG_DEBUG, ("%p VIDEO_MSE_JOIN_LATENCY = %f (%d ms) count=%d\n",
+                     this, latency, SECONDS_TO_MS(latency), mJoinLatency.Count()));
 }
 
 void HTMLMediaElement::UnbindFromTree(bool aDeep,
@@ -3664,6 +3678,23 @@ nsresult HTMLMediaElement::DispatchAsyncEvent(const nsAString& aName)
 
   nsCOMPtr<nsIRunnable> event = new nsAsyncEventRunner(aName, this);
   NS_DispatchToMainThread(event);
+
+  // Only collect rebuffer and stall rate stats for MSE video.
+  if (!mMediaSource) {
+    return NS_OK;
+  }
+
+  if ((aName.EqualsLiteral("play") || aName.EqualsLiteral("playing"))) {
+    mPlayTime.Start();
+    mRebufferTime.Pause();
+    mJoinLatency.Pause();
+  } else if (aName.EqualsLiteral("waiting")) {
+    mPlayTime.Pause();
+    mRebufferTime.Start();
+  } else if (aName.EqualsLiteral("pause")) {
+    mPlayTime.Pause();
+  }
+
   return NS_OK;
 }
 

dom/html/HTMLMediaElement.h

@@ -1354,6 +1354,51 @@ protected:
 
   ElementInTreeState mElementInTreeState;
 
+public:
+  // Helper class to measure times for MSE telemetry stats
+  class TimeDurationAccumulator {
+  public:
+    TimeDurationAccumulator()
+      : mCount(0)
+    {
+    }
+    void Start() {
+      if (IsStarted()) {
+        return;
+      }
+      mStartTime = TimeStamp::Now();
+    }
+    void Pause() {
+      if (!IsStarted()) {
+        return;
+      }
+      mSum += (TimeStamp::Now() - mStartTime);
+      mCount++;
+      mStartTime = TimeStamp();
+    }
+    bool IsStarted() const {
+      return !mStartTime.IsNull();
+    }
+    double Total() const {
+      return mSum.ToSeconds();
+    }
+    uint32_t Count() const {
+      return mCount;
+    }
+  private:
+    TimeStamp mStartTime;
+    TimeDuration mSum;
+    uint32_t mCount;
+  };
+private:
+  // Total time an MSE video has spent playing
+  TimeDurationAccumulator mPlayTime;
+
+  // Time spent buffering in an MSE video
+  TimeDurationAccumulator mRebufferTime;
+
+  // Time spent between video load and video playback.
+  TimeDurationAccumulator mJoinLatency;
 };
 
 } // namespace dom

dom/media/VideoUtils.h

@@ -148,8 +148,11 @@ static const int64_t USECS_PER_S = 1000000;
 // Number of microseconds per millisecond.
 static const int64_t USECS_PER_MS = 1000;
 
+// Converts milliseconds to seconds.
+#define MS_TO_SECONDS(ms) ((double)(ms) / (PR_MSEC_PER_SEC))
+
 // Converts seconds to milliseconds.
-#define MS_TO_SECONDS(s) ((double)(s) / (PR_MSEC_PER_SEC))
+#define SECONDS_TO_MS(s) ((int)((s) * (PR_MSEC_PER_SEC)))
 
 // Converts from seconds to microseconds. Returns failure if the resulting
 // integer is too big to fit in an int64_t.

toolkit/components/telemetry/Histograms.json

@@ -7399,6 +7399,25 @@
     "n_buckets": 16,
     "description": "The number of entries in persistent DataStorage (HSTS and HPKP data, basically)"
   },
+  "VIDEO_MSE_JOIN_LATENCY_MS" : {
+    "expires_in_version": "45",
+    "description": "Time in MS between MSE video load and playback",
+    "kind": "exponential",
+    "high": "30000",
+    "n_buckets": 50
+  },
+  "VIDEO_MSE_PLAY_TIME_MS" : {
+    "expires_in_version": "45",
+    "description": "Total time spent playing MSE video",
+    "kind": "exponential",
+    "high": "7200000",
+    "n_buckets": 100
+  },
+  "VIDEO_MSE_BUFFERING_COUNT" : {
+    "expires_in_version": "45",
+    "description": "Count of times that MSE video was buffering",
+    "kind": "count"
+  },
   "VIDEO_MSE_UNLOAD_STATE": {
     "expires_in_version": "45",
     "kind": "enumerated",