Convert IntelligibilityEnhancer to multi-threaded mode

webrtc/modules/audio_processing/noise_suppression_impl.cc

Index: webrtc/modules/audio_processing/noise_suppression_impl.cc
diff --git a/webrtc/modules/audio_processing/noise_suppression_impl.cc b/webrtc/modules/audio_processing/noise_suppression_impl.cc
index 7f19005924de76373ebe8547337e341ad0656767..aa979b6e73f82e02286fe30c351e0de1aff20e3d 100644
--- a/webrtc/modules/audio_processing/noise_suppression_impl.cc
+++ b/webrtc/modules/audio_processing/noise_suppression_impl.cc
@@ -200,4 +200,15 @@ std::vector<float> NoiseSuppressionImpl::NoiseEstimate() {
   return noise_estimate;
 }
 
+size_t NoiseSuppressionImpl::num_noise_bins() const {
+  rtc::CritScope cs(crit_);
+  size_t num_freq = 0u;

[hlundin-webrtc, 2016/03/08 10:28:48]

Exactly one of WEBRTC_NS_FLOAT and _FIXED must be defined, right? If so,
simplify this function:

{
  rtc::CritScope cs(crit_);
  #if defined(WEBRTC_NS_FLOAT)
  return WebRtcNs_num_freq();
  #elif defined(WEBRTC_NS_FIXED)
  return WebRtcNsx_num_freq();
  #else
  static_assert(false, "You are doing it wrong.")
  #endif
}

(If you don't want to verify that exactly one of the defines are set, skip the
static assert and make the #elif a simple #else.)

[kwiberg-webrtc, 2016/03/08 10:40:22]

This still doesn't fail if both are defined.

Also, it's customary to use #error and not static_assert(false) in situations
like this, both for historical reasons and because it's less complicated and
works in more places.

[aluebs-webrtc, 2016/03/08 10:53:00]

In general I think the functions with only one return statement are less bug
prone, but I can understand the argument for simplicity, so I accepted your
suggestion. I am not adding the verification, because, as kwiberg pointed out,
it doesn't fail if both are defined and because the whole file assumes one of
them to be defined (and that is how they are defined in audio_processing.gypi).
But if you think I should add this additional verification, I am happy to do so.

[hlundin-webrtc, 2016/03/08 13:35:19]

This is good. Don't add any verification. This is not the place for it. (And I
think you will get implicit verification that at least one is defined the way
you wrote it now.)

+#if defined(WEBRTC_NS_FLOAT)
+  num_freq = WebRtcNs_num_freq();
+#elif defined(WEBRTC_NS_FIXED)
+  num_freq = WebRtcNsx_num_freq();
+#endif
+  return num_freq;
+}
+
 }  // namespace webrtc