Add SincResampler ported from WebKit.

media/base/sinc_resampler_unittest.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+// MSVC++ requires this to be set before any other includes to get M_PI.
+#define _USE_MATH_DEFINES
+
+#include <cmath>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/stringprintf.h"
+#include "media/base/sinc_resampler.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using testing::_;
+
+namespace media {
+
+// Helper class to ensure ChunkedResample() functions properly.
+class MockSource {
+ public:
+  MOCK_METHOD2(ProvideInput, void(float* destination, int frames));
+};
+
+// Test requesting multiples of ChunkSize() frames results in the proper number
+// of callbacks.
+TEST(SincResamplerTest, ChunkedResample) {
+  MockSource mock_source;
+
+  // Choose a high ratio of input to output samples which will result in quick
+  // exhaustion of SincResampler's internal buffers.
+  static const double kSampleRateRatio = 192000.0 / 44100.0;
+  SincResampler resampler(
+      kSampleRateRatio,
+      base::Bind(&MockSource::ProvideInput, base::Unretained(&mock_source)));
+
+  static const int kChunks = 2;
+  int max_chunk_size = resampler.ChunkSize() * kChunks;
+  scoped_array<float> resampled_destination(new float[max_chunk_size]);
+
+  // Verify requesting ChunkSize() frames causes a single callback.
+  EXPECT_CALL(mock_source, ProvideInput(_, _)).Times(1);
+  resampler.Resample(resampled_destination.get(), resampler.ChunkSize());
+
+  // Verify requesting kChunks * ChunkSize() frames causes kChunks callbacks.
+  testing::Mock::VerifyAndClear(&mock_source);
+  EXPECT_CALL(mock_source, ProvideInput(_, _)).Times(kChunks);
+  resampler.Resample(resampled_destination.get(), max_chunk_size);
+}
+
+// Fake audio source for testing the resampler.  Generates a sinusoidal linear
+// chirp (http://en.wikipedia.org/wiki/Chirp) which can be tuned to stress the
+// resampler for the specific sample rate conversion being used.
+class SinusoidalLinearChirpSource {
+ public:
+  SinusoidalLinearChirpSource(int sample_rate, int samples,
+                              double max_frequency)
+      : sample_rate_(sample_rate),
+        total_samples_(samples),
+        max_frequency_(max_frequency),
+        current_index_(0) {
+    // Chirp rate.
+    double duration = static_cast<double>(total_samples_) / sample_rate_;
+    k_ = (max_frequency_ - kMinFrequency) / duration;
+  }
+
+  virtual ~SinusoidalLinearChirpSource() {}
+
+  void ProvideInput(float* destination, int frames) {
+    for (int i = 0; i < frames; ++i, ++current_index_) {
+      // Filter out frequencies higher than Nyquist.
+      if (Frequency(current_index_) > 0.5 * sample_rate_) {
+        destination[i] = 0;
+      } else {
+        // Calculate time in seconds.
+        double t = static_cast<double>(current_index_) / sample_rate_;
+
+        // Sinusoidal linear chirp.
+        destination[i] = sin(2 * M_PI * (kMinFrequency * t + (k_ / 2) * t * t));
+      }
+    }
+  }
+
+  double Frequency(int position) {
+    return kMinFrequency + position * (max_frequency_ - kMinFrequency)
+        / total_samples_;
+  }
+
+ private:
+  enum {
+    kMinFrequency = 5
+  };
+
+  double sample_rate_;
+  int total_samples_;
+  double max_frequency_;
+  double k_;
+  int current_index_;
+
+  DISALLOW_COPY_AND_ASSIGN(SinusoidalLinearChirpSource);
+};
+
+typedef std::tr1::tuple<int, int, double, double> SincResamplerTestData;
+class SincResamplerTestCase
+    : public testing::TestWithParam<SincResamplerTestData> {
+ public:
+  SincResamplerTestCase()
+      : input_rate_(std::tr1::get<0>(GetParam())),
+        output_rate_(std::tr1::get<1>(GetParam())),
+        rms_error_(std::tr1::get<2>(GetParam())),
+        low_freq_error_(std::tr1::get<3>(GetParam())) {
+  }
+
+  virtual ~SincResamplerTestCase() {}
+
+ protected:
+  int input_rate_;
+  int output_rate_;
+  double rms_error_;
+  double low_freq_error_;
+};
+
+// Tests resampling using a given input and output sample rate.
+TEST_P(SincResamplerTestCase, Resample) {
+  // Make comparisons using one second of data.
+  static const double kTestDurationSecs = 1;
+  int input_samples = kTestDurationSecs * input_rate_;
+  int output_samples = kTestDurationSecs * output_rate_;
+
+  // Nyquist frequency for the input sampling rate.
+  double input_nyquist_freq = 0.5 * input_rate_;
+
+  // Source for data to be resampled.
+  SinusoidalLinearChirpSource resampler_source(
+      input_rate_, input_samples, input_nyquist_freq);
+
+  SincResampler resampler(
+      input_rate_ / static_cast<double>(output_rate_),
+      base::Bind(&SinusoidalLinearChirpSource::ProvideInput,
+                 base::Unretained(&resampler_source)));
+
+  // TODO(dalecurtis): If we switch to AVX/SSE optimization, we'll need to
+  // allocate these on 32-byte boundaries and ensure they're sized % 32 bytes.
+  scoped_array<float> resampled_destination(new float[output_samples]);
+  scoped_array<float> pure_destination(new float[output_samples]);
+
+  // Generate resampled signal.
+  resampler.Resample(resampled_destination.get(), output_samples);
+
+  // Generate pure signal.
+  SinusoidalLinearChirpSource pure_source(
+      output_rate_, output_samples, input_nyquist_freq);
+  pure_source.ProvideInput(pure_destination.get(), output_samples);
+
+  // Range of the Nyquist frequency (0.5 * min(input rate, output_rate)) which
+  // we refer to as low and high.
+  static const double kLowFrequencyNyquistRange = 0.7;
+  static const double kHighFrequencyNyquistRange = 0.9;
+
+  // Calculate Root-Mean-Square-Error and maximum error for the resampling.
+  double sum_of_squares = 0;
+  double low_freq_max_error = 0;
+  double high_freq_max_error = 0;
+  for (int i = 0; i < output_samples; ++i) {
+    double error = fabs(resampled_destination[i] - pure_destination[i]);
+
+    if (pure_source.Frequency(i) < kLowFrequencyNyquistRange * 0.5
+        * std::min(input_rate_, output_rate_)) {
+      if (error > low_freq_max_error)
+        low_freq_max_error = error;
+    } else if (pure_source.Frequency(i) < kHighFrequencyNyquistRange * 0.5
+               * std::min(input_rate_, output_rate_)) {

[Chris Rogers, 2012/07/11 00:16:49]

Instead of repeating std::min(input_rate_, output_rate_) twice, you might
consider calculating this value once outside the loop.

[DaleCurtis, 2012/07/11 17:17:22]

Done.

+      if (error > high_freq_max_error)
+        high_freq_max_error = error;
+    }
+    // TODO(dalecurtis): Sanity check frequencies > kHighFrequencyNyquistRange.
+
+    sum_of_squares += error * error;
+  }
+
+  double rms_error = sqrt(sum_of_squares / output_samples);
+
+  // Convert each error to dbFS.
+  #define DBFS(x) 20 * log10(x)
+  rms_error = DBFS(rms_error);
+  low_freq_max_error = DBFS(low_freq_max_error);
+  high_freq_max_error = DBFS(high_freq_max_error);
+
+  EXPECT_LE(rms_error, rms_error_);
+  EXPECT_LE(low_freq_max_error, low_freq_error_);
+
+  // All conversions currently have a high frequency error around -6 dbFS.
+  static const double kHighFrequencyMaxError = -6.02435;
+  EXPECT_LE(high_freq_max_error, kHighFrequencyMaxError);
+}
+
+// Almost all conversions have an RMS error of arond -14 dbFS.
+static const double kResamplingRMSError = -14.5802;
+
+// Thresholds chosen arbitrarily based on what each resampling reported during
+// testing.  All thresholds are in dbFS, http://en.wikipedia.org/wiki/DBFS.
+INSTANTIATE_TEST_CASE_P(
+    SincResamplerTest, SincResamplerTestCase, testing::Values(
+        // To 44.1kHz
+        std::tr1::make_tuple(8000, 44100, kResamplingRMSError, -62.7323),
+        std::tr1::make_tuple(11025, 44100, kResamplingRMSError, -72.1958),
+        std::tr1::make_tuple(16000, 44100, kResamplingRMSError, -62.5423),
+        std::tr1::make_tuple(22050, 44100, kResamplingRMSError, -73.5389),
+        std::tr1::make_tuple(32000, 44100, kResamplingRMSError, -63.3289),
+        std::tr1::make_tuple(44100, 44100, kResamplingRMSError, -73.5364),
+        std::tr1::make_tuple(48000, 44100, -15.0114, -64.0425),
+        std::tr1::make_tuple(96000, 44100, -18.4991, -25.5177),
+        std::tr1::make_tuple(192000, 44100, -20.5068, -13.3184),
+
+        // To 48kHz
+        std::tr1::make_tuple(8000, 48000, kResamplingRMSError, -63.4359),
+        std::tr1::make_tuple(11025, 48000, kResamplingRMSError, -62.6140),
+        std::tr1::make_tuple(16000, 48000, kResamplingRMSError, -63.9629),
+        std::tr1::make_tuple(22050, 48000, kResamplingRMSError, -62.4224),
+        std::tr1::make_tuple(32000, 48000, kResamplingRMSError, -64.0417),
+        std::tr1::make_tuple(44100, 48000, kResamplingRMSError, -62.6364),
+        std::tr1::make_tuple(48000, 48000, kResamplingRMSError, -73.5241),
+        std::tr1::make_tuple(96000, 48000, -18.403, -28.4466),
+        std::tr1::make_tuple(192000, 48000, -20.4382, -14.1110),
+
+        // To 96kHz
+        std::tr1::make_tuple(8000, 96000, kResamplingRMSError, -63.1999),
+        std::tr1::make_tuple(11025, 96000, kResamplingRMSError, -62.6140),
+        std::tr1::make_tuple(16000, 96000, kResamplingRMSError, -63.3983),
+        std::tr1::make_tuple(22050, 96000, kResamplingRMSError, -62.4224),
+        std::tr1::make_tuple(32000, 96000, kResamplingRMSError, -63.9571),
+        std::tr1::make_tuple(44100, 96000, kResamplingRMSError, -62.6364),
+        std::tr1::make_tuple(48000, 96000, kResamplingRMSError, -73.5241),
+        std::tr1::make_tuple(96000, 96000, kResamplingRMSError, -73.5266),
+        std::tr1::make_tuple(192000, 96000, kResamplingRMSError, -28.4128),
+
+        // To 192kHz
+        std::tr1::make_tuple(8000, 192000, kResamplingRMSError, -63.1017),
+        std::tr1::make_tuple(11025, 192000, kResamplingRMSError, -62.6140),
+        std::tr1::make_tuple(16000, 192000, kResamplingRMSError, -63.1433),
+        std::tr1::make_tuple(22050, 192000, kResamplingRMSError, -62.4231),
+        std::tr1::make_tuple(32000, 192000, kResamplingRMSError, -63.3822),
+        std::tr1::make_tuple(44100, 192000, kResamplingRMSError, -62.6364),
+        std::tr1::make_tuple(48000, 192000, kResamplingRMSError, -73.4483),
+        std::tr1::make_tuple(96000, 192000, kResamplingRMSError, -73.5266),
+        std::tr1::make_tuple(192000, 192000, kResamplingRMSError, -73.5266)));
+
+}  // namespace media