Added UMA metrics for MediaSourcePlayer and MediaCodecPlayer

media/base/android/media_statistics.cc

Index: media/base/android/media_statistics.cc
diff --git a/media/base/android/media_statistics.cc b/media/base/android/media_statistics.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d898e07e843270f846f6376c9b38c73b7c760bd4
--- /dev/null
+++ b/media/base/android/media_statistics.cc
@@ -0,0 +1,122 @@
+// Copyright 2015 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 "media/base/android/media_statistics.h"
+
+#include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
+#include "media/base/android/demuxer_stream_player_params.h"
+
+namespace media {
+
+// Minimum playback interval to report.
+const int kMinDurationInSeconds = 2;
+
+// Maximum playback interval to report.
+const int kMaxDurationInSeconds = 3600;
+
+// Number of slots in the histogram for playback interval.
+const int kNumDurationSlots = 50;
+
+// For easier reading.
+const int kOneMillion = 1000000;
+
+void FrameStatistics::IncrementLateFrameCount() {
+  // Do not collect the late frame if this is the first frame after the start.
+  // Right now we do not want to consider the late video frame which is the
+  // first after preroll, preroll may be inacurate in this respect.
+  // The first audio frame cannot be late by definition and by not considering
+  // it we can simplify audio decoder code.
+  if (total == 1)

[Tima Vaisburd, 2015/10/02 00:44:32]

I accidently deleted this check in the prior PS, restored. 

+    return;
+
+  ++late;
+}
+
+MediaStatistics::MediaStatistics() {}
+
+MediaStatistics::~MediaStatistics() {}
+
+void MediaStatistics::Start(base::TimeDelta current_playback_time) {
+  DVLOG(1) << __FUNCTION__;
+
+  if (start_time_ == kNoTimestamp()) {

[Tima Vaisburd, 2015/10/02 00:44:32]

I changed the Start() semantic to follow StopAndReport(): only the first call in
a row takes effect. With this we can keep the Start() calls where they are even
if MediaSourcePlayer reporting starvations very frequently. 

+    Clear();
+    start_time_ = current_playback_time;
+  }
+}
+
+void MediaStatistics::StopAndReport(base::TimeDelta current_playback_time) {
+  DVLOG(1) << __FUNCTION__;
+
+  if (start_time_ == kNoTimestamp())
+    return;  // skip if there was no prior Start().
+
+  base::TimeDelta duration = current_playback_time - start_time_;
+
+  // Reset start time.
+  start_time_ = kNoTimestamp();
+
+  if (duration < base::TimeDelta::FromSeconds(kMinDurationInSeconds))
+    return;  // duration is too short.
+
+  if (duration > base::TimeDelta::FromSeconds(kMaxDurationInSeconds))
+    return;  // duration is too long.
+
+  Report(duration);
+}
+
+void MediaStatistics::Clear() {
+  start_time_ = kNoTimestamp();
+  audio_frame_stats_.Clear();
+  video_frame_stats_.Clear();
+  num_starvations_ = 0;
+}
+
+void MediaStatistics::Report(base::TimeDelta duration) {
+  DVLOG(1) << __FUNCTION__ << " duration:" << duration
+           << " audio frames:"
+           << audio_frame_stats_.late << "/" << audio_frame_stats_.total
+           << " video frames:"
+           << video_frame_stats_.late << "/" << video_frame_stats_.total
+           << " starvations:" << num_starvations_;
+
+  // Playback duration is the time interval between the moment playback starts
+  // and the moment it is interrupted either by stopping or by seeking, changing
+  // to full screen, minimizing the browser etc. The interval is measured by
+  // media time.
+
+  UMA_HISTOGRAM_CUSTOM_TIMES(
+      "Media.MSE.PlaybackDuration", duration,
+      base::TimeDelta::FromSeconds(kMinDurationInSeconds),
+      base::TimeDelta::FromSeconds(kMaxDurationInSeconds), kNumDurationSlots);
+
+  // Number of late frames per one million frames.
+  // We expect the ratios of the late frames to the total number of frames to be
+  // less than 1%, therefore after multiplying by one millon the range should be
+  // [0, 10000].
+
+  if (audio_frame_stats_.total) {
+    UMA_HISTOGRAM_COUNTS(
+        "Media.MSE.LateAudioFrames",
+        kOneMillion * audio_frame_stats_.late / audio_frame_stats_.total);
+  }
+
+  if (video_frame_stats_.total) {
+    UMA_HISTOGRAM_COUNTS(
+        "Media.MSE.LateVideoFrames",
+        kOneMillion * video_frame_stats_.late / video_frame_stats_.total);
+  }
+
+  // Number of starvations per one million frames.
+
+  uint32_t total_frames = audio_frame_stats_.total ? audio_frame_stats_.total
+                                                   : video_frame_stats_.total;
+  if (total_frames) {
+    UMA_HISTOGRAM_COUNTS("Media.MSE.Starvations",
+                         kOneMillion * num_starvations_ / total_frames);
+  }
+}
+
+}  // namespace media