Add UMA reporting for audio hardware parameters.

media/audio/audio_output_resampler.cc

Index: media/audio/audio_output_resampler.cc
diff --git a/media/audio/audio_output_resampler.cc b/media/audio/audio_output_resampler.cc
index e67e2771649443f2c6c494fef07940c4162ca19a..be4802a6f6d6bd420c6cfd9717a549ed41f2ac21 100644
--- a/media/audio/audio_output_resampler.cc
+++ b/media/audio/audio_output_resampler.cc
@@ -8,11 +8,13 @@
 #include "base/bind_helpers.h"
 #include "base/compiler_specific.h"
 #include "base/message_loop.h"
+#include "base/metrics/histogram.h"
 #include "base/time.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_output_dispatcher_impl.h"
 #include "media/audio/audio_output_proxy.h"
 #include "media/audio/audio_util.h"
+#include "media/audio/sample_rates.h"
 #include "media/base/audio_pull_fifo.h"
 #include "media/base/multi_channel_resampler.h"
 
@@ -77,6 +79,24 @@ AudioOutputResampler::AudioOutputResampler(AudioManager* audio_manager,
   // we've stabilized the issues there.
   dispatcher_ = new AudioOutputDispatcherImpl(
       audio_manager, output_params, close_delay);
+
+  // Fake enum histogram to get exact integral buckets.  Expect to never see
+  // any values over 32 and even that is huge.
+  UMA_HISTOGRAM_ENUMERATION(
+      "Media.HardwareAudioBitsPerChannel", output_params.bits_per_sample(),
+      40);

[scherkus (not reviewing), 2012/09/11 16:53:31]

not worth enumifying a la sample rate?

[DaleCurtis, 2012/09/11 17:35:59]

Copy/pasted from AudioDecoderConfig. You tell me.

+  UMA_HISTOGRAM_ENUMERATION(
+      "Media.HardwareAudioChannelLayout", output_params.channel_layout(),

[scherkus (not reviewing), 2012/09/11 16:53:31]

I thought we only got hardware channel *count* and not layout?


If we do indeed track layout, to preserve accuracy of UMA data over time you'll
have to assign values to ChannelLayout + include documentation to not re-use
values (see PipelineStatus for an example)

[DaleCurtis, 2012/09/11 17:35:59]

This is all a copy paste of what's in AudioDecoderConfig? Why would I need to
add more for ChannelLayout here but not there?

We really don't have either. This code will track the input parameters
currently. If we want to track the actual hardware value I'll need to #if
WINDOWS this as well as muck with audio manager to expose that information in a
platform agnostic manner.

(We don't want to put this in GetPreferredLowLatencyBlahBlahBlah right now since
it's being handled at the output device instead of here).

[DaleCurtis, 2012/09/12 09:50:57]

Done. I'm now pulling the actual hardware channel count for Windows. 

+      CHANNEL_LAYOUT_MAX);
+  AudioSampleRate asr = media::AsAudioSampleRate(output_params.sample_rate());
+  if (asr != kUnexpectedAudioSampleRate) {
+    UMA_HISTOGRAM_ENUMERATION(
+        "Media.HardwareAudioSamplesPerSecond", asr, kUnexpectedAudioSampleRate);
+  } else {
+    UMA_HISTOGRAM_COUNTS(
+        "Media.HardwareAudioSamplesPerSecondUnexpected",
+        output_params.sample_rate());
+  }
 }
 
 AudioOutputResampler::~AudioOutputResampler() {}