Reduce cost of PushSincResampler::Resample().

Ideally, PushSincResampler would have very little overhead on
SincResampler. This gets closer to that ideal.

Replace std::min/max and floor with inline functions. Add a benchmark
test to verify the improvement.

On a MacBook Retina, this results in PushSincResampler::Resample()
accounting for ~1% of CPU usage on voe_cmd_test vs the earlier ~2%
(with ISAC16 and 48 kHz audio devices).

Using the new benchmark, this results in a performance improvement of:
16 -> 44.1 : 1.7x
16 -> 48   : 1.9x
32 -> 44.1 : 1.6x
32 -> 48   : 1.7x
44.1 -> 16 : 1.5x
44.1 -> 32 : 1.7x
44.1 -> 48 : 1.7x
48 -> 16   : 1.5x
48 -> 32   : 1.5x
48 -> 44.1 : 1.8x

R=turaj@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2157005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4695 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/common_audio/audio_util_unittest.cc

@@ -20,6 +20,20 @@ void ExpectArraysEq(const int16_t* ref, const int16_t* test, int length) {
   }
 }
 
+TEST(AudioUtilTest, Clamp) {
+  EXPECT_EQ(1000.f, ClampInt16(1000.f));
+  EXPECT_EQ(32767.f, ClampInt16(32767.5f));
+  EXPECT_EQ(-32768.f, ClampInt16(-32768.5f));
+}
+
+TEST(AudioUtilTest, Round) {
+  EXPECT_EQ(0, RoundToInt16(0.f));
+  EXPECT_EQ(0, RoundToInt16(0.4f));
+  EXPECT_EQ(1, RoundToInt16(0.5f));
+  EXPECT_EQ(0, RoundToInt16(-0.4f));
+  EXPECT_EQ(-1, RoundToInt16(-0.5f));
+}
+
 TEST(AudioUtilTest, InterleavingStereo) {
   const int16_t kInterleaved[] = {2, 3, 4, 9, 8, 27, 16, 81};
   const int kSamplesPerChannel = 4;

webrtc/common_audio/include/audio_util.h

@@ -15,6 +15,20 @@
 
 namespace webrtc {
 
+// Clamp the floating |value| to the range representable by an int16_t.
+static inline float ClampInt16(float value) {
+  const float kMaxInt16 = 32767.f;
+  const float kMinInt16 = -32768.f;
+  return value < kMinInt16 ? kMinInt16 :
+      (value > kMaxInt16 ? kMaxInt16 : value);
+}
+
+// Return a rounded int16_t of the floating |value|. Doesn't handle overflow;
+// use ClampInt16 if necessary.
+static inline int16_t RoundToInt16(float value) {
+  return static_cast<int16_t>(value < 0.f ? value - 0.5f : value + 0.5f);
+}
+
 // Deinterleave audio from |interleaved| to the channel buffers pointed to
 // by |deinterleaved|. There must be sufficient space allocated in the
 // |deinterleaved| buffers (|num_channel| buffers with |samples_per_channel|

webrtc/common_audio/resampler/push_sinc_resampler.cc

@@ -8,13 +8,11 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#include "webrtc/common_audio/include/audio_util.h"
 #include "webrtc/common_audio/resampler/push_sinc_resampler.h"
 
-#include <math.h>
 #include <string.h>
 
-#include <algorithm>
-
 namespace webrtc {
 
 PushSincResampler::PushSincResampler(int source_frames,
@@ -61,10 +59,8 @@ int PushSincResampler::Resample(const int16_t* source,
     resampler_->Resample(resampler_->ChunkSize(), float_buffer_.get());
 
   resampler_->Resample(destination_frames_, float_buffer_.get());
-  for (int i = 0; i < destination_frames_; ++i) {
-    float clipped = std::max(std::min(float_buffer_[i], 32767.0f), -32768.0f);
-    destination[i] = static_cast<int16_t>(floor(clipped + 0.5));
-  }
+  for (int i = 0; i < destination_frames_; ++i)
+    destination[i] = RoundToInt16(ClampInt16(float_buffer_[i]));
   source_ptr_ = NULL;
   return destination_frames_;
 }

webrtc/common_audio/resampler/push_sinc_resampler_unittest.cc

@@ -15,6 +15,7 @@
 #include "webrtc/common_audio/resampler/push_sinc_resampler.h"
 #include "webrtc/common_audio/resampler/sinusoidal_linear_chirp_source.h"
 #include "webrtc/system_wrappers/interface/scoped_ptr.h"
+#include "webrtc/system_wrappers/interface/tick_util.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
@@ -39,6 +40,59 @@ class PushSincResamplerTest
   double low_freq_error_;
 };
 
+class ZeroSource : public SincResamplerCallback {
+ public:
+  void Run(int frames, float* destination) {
+    memset(destination, 0, sizeof(float) * frames);
+  }
+};
+
+// Disabled because it takes too long to run routinely. Use for performance
+// benchmarking when needed.
+TEST_P(PushSincResamplerTest, DISABLED_ResampleBenchmark) {
+  const int input_samples = input_rate_ / 100;
+  const int output_samples = output_rate_ / 100;
+  const int kResampleIterations = 200000;
+
+  // Source for data to be resampled.
+  ZeroSource resampler_source;
+
+  scoped_array<float> resampled_destination(new float[output_samples]);
+  scoped_array<float> source(new float[input_samples]);
+  scoped_array<int16_t> source_int(new int16_t[input_samples]);
+  scoped_array<int16_t> destination_int(new int16_t[output_samples]);
+
+  resampler_source.Run(input_samples, source.get());
+  for (int i = 0; i < input_samples; ++i) {
+    source_int[i] = static_cast<int16_t>(floor(32767 * source[i] + 0.5));
+  }
+
+  printf("Benchmarking %d iterations of %d Hz -> %d Hz:\n",
+         kResampleIterations, input_rate_, output_rate_);
+  const double io_ratio = input_rate_ / static_cast<double>(output_rate_);
+  SincResampler sinc_resampler(io_ratio, SincResampler::kDefaultRequestSize,
+                               &resampler_source);
+  TickTime start = TickTime::Now();
+  for (int i = 0; i < kResampleIterations; ++i) {
+    sinc_resampler.Resample(output_samples, resampled_destination.get());
+  }
+  double total_time_sinc_us = (TickTime::Now() - start).Microseconds();
+  printf("SincResampler took %.2f us per frame.\n",
+         total_time_sinc_us / kResampleIterations);
+
+  PushSincResampler resampler(input_samples, output_samples);
+  start = TickTime::Now();
+  for (int i = 0; i < kResampleIterations; ++i) {
+    EXPECT_EQ(output_samples,
+              resampler.Resample(source_int.get(), input_samples,
+                                 destination_int.get(), output_samples));
+  }
+  double total_time_us = (TickTime::Now() - start).Microseconds();
+  printf("PushSincResampler took %.2f us per frame; which is a %.1f%% overhead "
+         "on SincResampler.\n\n", total_time_us / kResampleIterations,
+         (total_time_us - total_time_sinc_us) / total_time_sinc_us * 100);
+}
+
 // Tests resampling using a given input and output sample rate.
 TEST_P(PushSincResamplerTest, Resample) {
   // Make comparisons using one second of data.