Fixing sample-rate dependent band-split filter issues in AEC3

webrtc/modules/audio_processing/aec3/aec3_common.h

Index: webrtc/modules/audio_processing/aec3/aec3_common.h
diff --git a/webrtc/modules/audio_processing/aec3/aec3_common.h b/webrtc/modules/audio_processing/aec3/aec3_common.h
index f03a7e33d29f25370d39f621679b1cccdfa9f0c1..659a9b24a2f596ff8f99bebc8e3d1ca47f6dbd39 100644
--- a/webrtc/modules/audio_processing/aec3/aec3_common.h
+++ b/webrtc/modules/audio_processing/aec3/aec3_common.h
@@ -68,9 +68,15 @@ constexpr size_t kRenderTransferQueueSize = kMaxApiCallsJitterBlocks / 2;
 static_assert(2 * kRenderTransferQueueSize >= kMaxApiCallsJitterBlocks,
               "Requirement to ensure buffer overflow detection");
 
+// TODO(peah): Integrate this with how it is done inside audio_processing_impl.
 constexpr size_t NumBandsForRate(int sample_rate_hz) {
+#ifdef WEBRTC_ARCH_ARM_FAMILY
+  return std::min(2, static_cast<size_t>(

[hlundin-webrtc, 2017/04/07 09:55:06]

I think this would be more readable as 
return static_cast<size_t>(sample_rate_hz == 8000 ? 1 : 2);

[hlundin-webrtc, 2017/04/07 09:56:35]

My bad. How about
return static_cast<size_t>(sample_rate_hz <= 16000 ? 1 : 2);

[peah-webrtc, 2017/04/07 10:00:16]

Awesome! Much better!
Done.

+                         sample_rate_hz == 8000 ? 1 : sample_rate_hz / 16000));
+#else
   return static_cast<size_t>(sample_rate_hz == 8000 ? 1
                                                     : sample_rate_hz / 16000);
+#endif
 }
 constexpr int LowestBandRate(int sample_rate_hz) {
   return sample_rate_hz == 8000 ? sample_rate_hz : 16000;
@@ -87,7 +93,11 @@ Aec3Optimization DetectOptimization();
 static_assert(1 == NumBandsForRate(8000), "Number of bands for 8 kHz");
 static_assert(1 == NumBandsForRate(16000), "Number of bands for 16 kHz");
 static_assert(2 == NumBandsForRate(32000), "Number of bands for 32 kHz");
+#ifdef WEBRTC_ARCH_ARM_FAMILY
+static_assert(2 == NumBandsForRate(48000), "Number of bands for 48 kHz");
+#else
 static_assert(3 == NumBandsForRate(48000), "Number of bands for 48 kHz");
+#endif
 
 static_assert(8000 == LowestBandRate(8000), "Sample rate of band 0 for 8 kHz");
 static_assert(16000 == LowestBandRate(16000),