[Chromecast] Add metrics for logging platform A/V bitrate estimates.

chromecast/media/cma/pipeline/audio_pipeline_impl.cc

Index: chromecast/media/cma/pipeline/audio_pipeline_impl.cc
diff --git a/chromecast/media/cma/pipeline/audio_pipeline_impl.cc b/chromecast/media/cma/pipeline/audio_pipeline_impl.cc
index ab5478b7e7d0c5f5e85820262bd15b893a3a60a2..7c5ee777bd86b8fd510f457953f2877556dd6022 100644
--- a/chromecast/media/cma/pipeline/audio_pipeline_impl.cc
+++ b/chromecast/media/cma/pipeline/audio_pipeline_impl.cc
@@ -8,6 +8,8 @@
 #include <utility>
 
 #include "base/bind.h"
+#include "base/time/time.h"
+#include "chromecast/base/metrics/cast_metrics_helper.h"
 #include "chromecast/media/cma/base/buffering_defs.h"
 #include "chromecast/media/cma/base/cma_logging.h"
 #include "chromecast/media/cma/base/coded_frame_provider.h"
@@ -20,12 +22,25 @@ namespace media {
 
 namespace {
 const size_t kMaxAudioFrameSize = 32 * 1024;
+
+void LogEstimatedAudioBitrate(int bitrate) {
+  CMALOG(kLogControl) << "Estimated audio bitrate is " << bitrate << " kbps";
+  chromecast::metrics::CastMetricsHelper* metrics_helper =
+      chromecast::metrics::CastMetricsHelper::GetInstance();

[halliwell, 2016/03/10 17:57:54]

nit, no need for 'chromecast::'

[ejason, 2016/03/11 00:24:45]

Done.

+  metrics_helper->RecordSimpleActionWithValue("Cast.Platform.AudioBitrate",
+                                              bitrate);
+}
+
 }
 
 AudioPipelineImpl::AudioPipelineImpl(
     MediaPipelineBackend::AudioDecoder* decoder,
     const AvPipelineClient& client)
-    : AvPipelineImpl(decoder, client), audio_decoder_(decoder) {
+    : AvPipelineImpl(decoder, client),
+      audio_decoder_(decoder),
+      last_sample_time_(base::Time()),
+      elapsed_time_delta_(base::TimeDelta()),
+      audio_bytes_for_bitrate_estimation_(0) {
   DCHECK(audio_decoder_);
 }
 
@@ -84,6 +99,25 @@ void AudioPipelineImpl::UpdateStatistics() {
   delta_stats.audio_bytes_decoded =
       current_stats.audio_bytes_decoded - previous_stats_.audio_bytes_decoded;
 
+  base::Time current_time = base::Time::Now();
+  elapsed_time_delta_ += current_time - last_sample_time_;

[halliwell, 2016/03/10 17:57:54]

If the first time this function is called, we're in Playing state, then
last_sample_time_ is base::Time(), elapsed_time_delta_ will be incorrect and we
could log an incorrect stat?

[ejason, 2016/03/11 00:24:45]

I've updated the new logic to handle the first-time-the-function-is-called case.

+  audio_bytes_for_bitrate_estimation_ += delta_stats.audio_bytes_decoded;
+
+  if (state() != kPlaying) {
+    // Invalidate any data that was collected in a window where we were not in
+    // the playing state.
+    elapsed_time_delta_ = base::TimeDelta::FromSeconds(0);
+    audio_bytes_for_bitrate_estimation_ = 0;

[halliwell, 2016/03/10 17:57:54]

shouldn't we reset these things on state transitions?

What if we get this sequence:
* Gather stats
* Pause
* Play
* Gather stats

then we're taking into account a time period when we weren't playing.

[ejason, 2016/03/11 00:24:45]

The state transitions are handled in media_pipeline_impl_, so I moved this logic
there. That also addresses the point on duplication.

+  } else if (elapsed_time_delta_.InMilliseconds() > 5000) {
+    int estimated_bitrate_in_kbps = 8 * audio_bytes_for_bitrate_estimation_ /
+                                    elapsed_time_delta_.InMilliseconds();
+    if (estimated_bitrate_in_kbps > 0) {
+      LogEstimatedAudioBitrate(estimated_bitrate_in_kbps);
+    }
+    elapsed_time_delta_ = base::TimeDelta::FromSeconds(0);
+    audio_bytes_for_bitrate_estimation_ = 0;
+  }
+  last_sample_time_ = current_time;
   previous_stats_ = current_stats;
 
   client().statistics_cb.Run(delta_stats);