AEC: Add UMA logging of buffer re-alignment

webrtc/modules/audio_processing/aec/aec_core.cc

Index: webrtc/modules/audio_processing/aec/aec_core.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_core.cc b/webrtc/modules/audio_processing/aec/aec_core.cc
index 2cb6dd2ce7664cfc302b388644ccd77fca44c43a..4c109d7d9ce50cfe1455c5ad7b317c6c14bac8a3 100644
--- a/webrtc/modules/audio_processing/aec/aec_core.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core.cc
@@ -33,9 +33,37 @@ extern "C" {
 #include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
 #include "webrtc/modules/audio_processing/utility/delay_estimator_wrapper.h"
 #include "webrtc/system_wrappers/include/cpu_features_wrapper.h"
+#include "webrtc/system_wrappers/include/metrics.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
+namespace {
+enum class DelaySource {
+  kSystemDelay,    // The delay values come from the OS.
+  kDelayAgnostic,  // The delay values come from the DA-AEC.
+};
+
+constexpr int kMinDelayLogValue = -200;
+constexpr int kMaxDelayLogValue = 200;
+constexpr int kNumDelayLogBuckets = 100;
+
+void MaybeLogDelayAdjustment(int moved_ms, DelaySource source) {
+  if (moved_ms == 0)

[peah-webrtc, 2016/05/18 10:54:19]

I'd rather put this check when calling the method. It is more explicit I think,
and cheaper.  But I'm fully fine with how it is here as well.

+    return;
+  switch (source) {
+    case DelaySource::kSystemDelay:
+      RTC_HISTOGRAM_COUNTS("WebRTC.Audio.AecDelayAdjustmentMsSystemValue",
+                           moved_ms, kMinDelayLogValue, kMaxDelayLogValue,
+                           kNumDelayLogBuckets);
+      return;
+    case DelaySource::kDelayAgnostic:
+      RTC_HISTOGRAM_COUNTS("WebRTC.Audio.AecDelayAdjustmentMsAgnosticValue",
+                           moved_ms, kMinDelayLogValue, kMaxDelayLogValue,
+                           kNumDelayLogBuckets);
+      return;
+  }
+}
+}  // namespace
 
 // Buffer size (samples)
 static const size_t kBufSizePartitions = 250;  // 1 second of audio in 16 kHz.
@@ -1785,11 +1813,15 @@ void WebRtcAec_ProcessFrames(AecCore* aec,
       // rounding, like -16.
       int move_elements = (aec->knownDelay - knownDelay - 32) / PART_LEN;
       int moved_elements = WebRtc_MoveReadPtr(aec->far_time_buf, move_elements);
+      MaybeLogDelayAdjustment(moved_elements * (aec->sampFreq == 8000 ? 8 : 4),

[peah-webrtc, 2016/05/18 10:54:19]

I'd rather put the if-statement contained inside the method around the emthod
call, i.e., 
if (moved_elements > 0) {
MaybeLogDelayAdjustment();
}

but I leave it up to you to decide that.

+                              DelaySource::kSystemDelay);
       aec->knownDelay -= moved_elements * PART_LEN;
     } else {
       // 2 b) Apply signal based delay correction.
       int move_elements = SignalBasedDelayCorrection(aec);
       int moved_elements = WebRtc_MoveReadPtr(aec->far_time_buf, move_elements);
+      MaybeLogDelayAdjustment(moved_elements * (aec->sampFreq == 8000 ? 8 : 4),
+                              DelaySource::kDelayAgnostic);
       int far_near_buffer_diff =
           WebRtc_available_read(aec->far_time_buf) -
           WebRtc_available_read(aec->nearFrBuf) / PART_LEN;