Add SincResampler ported from WebKit.

This is a partial port of WebAudio's SincResampler from WebKit formatted and
culled for use by Chrome Media.

We can't directly use the one in WebKit as it's layed under a ton of abstraction
and is tightly coupled with WebKit objects.

Test generates a swept sine wave and calculates the RMS error for common sample
rates (via UMA stats).

MultiChannelResampler and AudioRenderMixer changes to support resampling will
come in later CLs.

The 1000 ft view is that MultiChannelResampler will implement SincResampler::
AudioSourceProvider and AudioRendererMixer will implement a new
MultiChannelResampler::MultiChannelAudioSourceProvider interface.

When resampling is necessary AudioRenderMixer will feed itself into a
MultiChannelResampler instance which will poll data as necessary and feed it
channel by channel into a set of SincResamplers (one for each channel).

We want to resample post-mixing since resampling is a much more expensive
operation.

Original for reference:
http://git.chromium.org/gitweb/?p=external/Webkit.git&a=blob&f=Source/WebCore/platform/audio/SincResampler.cpp

Visual plot of 44100 to 48000 for reference; red line is the resampled signal
and the green line is the reference signal. Ideally only the pure signal (green)
should be seen.  Any bit of the resampled signal showing (red) is where the
resampling algorithm is incorrect: http://i.imgur.com/1vsaI.png

BUG=133637
TEST=New unittests.

Review URL: https://chromiumcodereview.appspot.com/10702050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@146219 0039d316-1c4b-4281-b951-d872f2087c98

media/base/sinc_resampler.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.
+//
+// Input buffer layout, dividing the total buffer into regions (r0_ - r5_):
+//
+// |----------------|-----------------------------------------|----------------|
+//
+//                                   kBlockSize + kKernelSize / 2
+//                   <--------------------------------------------------------->
+//                                              r0_
+//
+//  kKernelSize / 2   kKernelSize / 2         kKernelSize / 2   kKernelSize / 2
+// <---------------> <--------------->       <---------------> <--------------->
+//        r1_               r2_                     r3_               r4_
+//
+//                                                     kBlockSize
+//                                     <--------------------------------------->
+//                                                        r5_
+//
+// The algorithm:
+//
+// 1) Consume input frames into r0_ (r1_ is zero-initialized).
+// 2) Position kernel centered at start of r0_ (r2_) and generate output frames
+//    until kernel is centered at start of r4_ or we've finished generating all
+//    the output frames.
+// 3) Copy r3_ to r1_ and r4_ to r2_.
+// 4) Consume input frames into r5_ (zero-pad if we run out of input).
+// 5) Goto (2) until all of input is consumed.
+//
+// Note: we're glossing over how the sub-sample handling works with
+// |virtual_source_idx_|, etc.
+
+// MSVC++ requires this to be set before any other includes to get M_PI.
+#define _USE_MATH_DEFINES
+
+#include "media/base/sinc_resampler.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+
+namespace media {
+
+enum {
+  // The kernel size can be adjusted for quality (higher is better) at the
+  // expense of performance.  Must be an even number.
+  // TODO(dalecurtis): Test performance to see if we can jack this up to 64+.
+  kKernelSize = 32,
+
+  // The number of destination frames generated per processing pass.  Affects
+  // how often and for how much SincResampler calls back for input.  Must be
+  // greater than kKernelSize.
+  kBlockSize = 512,
+
+  // The kernel offset count is used for interpolation and is the number of
+  // sub-sample kernel shifts.  Can be adjusted for quality (higher is better)
+  // at the expense of allocating more memory.
+  kKernelOffsetCount = 32,
+  kKernelStorageSize = kKernelSize * (kKernelOffsetCount + 1),
+
+  // The size (in samples) of the internal buffer used by the resampler.
+  kBufferSize = kBlockSize + kKernelSize
+};
+
+SincResampler::SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb)
+    : io_sample_rate_ratio_(io_sample_rate_ratio),
+      virtual_source_idx_(0),
+      buffer_primed_(false),
+      read_cb_(read_cb),
+      // TODO(dalecurtis): When we switch to AVX/SSE optimization, we'll need to
+      // allocate with 32-byte alignment and ensure they're sized % 32 bytes.
+      kernel_storage_(new float[kKernelStorageSize]),
+      input_buffer_(new float[kBufferSize]),
+      // Setup various region pointers in the buffer (see diagram above).
+      r0_(input_buffer_.get() + kKernelSize / 2),
+      r1_(input_buffer_.get()),
+      r2_(r0_),
+      r3_(r0_ + kBlockSize - kKernelSize / 2),
+      r4_(r0_ + kBlockSize),
+      r5_(r0_ + kKernelSize / 2) {
+  DCHECK_EQ(kKernelSize % 2, 0) << "kKernelSize must be even!";
+  DCHECK_GT(kBlockSize, kKernelSize)
+      << "kBlockSize must be greater than kKernelSize!";
+  // Basic sanity checks to ensure buffer regions are laid out correctly:
+  // r0_ and r2_ should always be the same position.
+  DCHECK_EQ(r0_, r2_);
+  // r1_ at the beginning of the buffer.
+  DCHECK_EQ(r1_, input_buffer_.get());
+  // r1_ left of r2_, r2_ left of r5_ and r1_, r2_ size correct.
+  DCHECK_EQ(r2_ - r1_, r5_ - r2_);
+  // r3_ left of r4_, r5_ left of r0_ and r3_ size correct.
+  DCHECK_EQ(r4_ - r3_, r5_ - r0_);
+  // r3_, r4_ size correct and r4_ at the end of the buffer.
+  DCHECK_EQ(r4_ + (r4_ - r3_), r1_ + kBufferSize);
+  // r5_ size correct and at the end of the buffer.
+  DCHECK_EQ(r5_ + kBlockSize, r1_ + kBufferSize);
+
+  memset(kernel_storage_.get(), 0,
+         sizeof(*kernel_storage_.get()) * kKernelStorageSize);
+  memset(input_buffer_.get(), 0, sizeof(*input_buffer_.get()) * kBufferSize);
+
+  InitializeKernel();
+}
+
+SincResampler::~SincResampler() {}
+
+void SincResampler::InitializeKernel() {
+  // Blackman window parameters.
+  static const double kAlpha = 0.16;
+  static const double kA0 = 0.5 * (1.0 - kAlpha);
+  static const double kA1 = 0.5;
+  static const double kA2 = 0.5 * kAlpha;
+
+  // |sinc_scale_factor| is basically the normalized cutoff frequency of the
+  // low-pass filter.
+  double sinc_scale_factor =
+      io_sample_rate_ratio_ > 1.0 ? 1.0 / io_sample_rate_ratio_ : 1.0;
+
+  // The sinc function is an idealized brick-wall filter, but since we're
+  // windowing it the transition from pass to stop does not happen right away.
+  // So we should adjust the low pass filter cutoff slightly downward to avoid
+  // some aliasing at the very high-end.
+  // TODO(crogers): this value is empirical and to be more exact should vary
+  // depending on kKernelSize.
+  sinc_scale_factor *= 0.9;
+
+  // Generates a set of windowed sinc() kernels.
+  // We generate a range of sub-sample offsets from 0.0 to 1.0.
+  for (int offset_idx = 0; offset_idx <= kKernelOffsetCount; ++offset_idx) {
+    double subsample_offset =
+        static_cast<double>(offset_idx) / kKernelOffsetCount;
+
+    for (int i = 0; i < kKernelSize; ++i) {
+      // Compute the sinc with offset.
+      double s =
+          sinc_scale_factor * M_PI * (i - kKernelSize / 2 - subsample_offset);
+      double sinc = (!s ? 1.0 : sin(s) / s) * sinc_scale_factor;
+
+      // Compute Blackman window, matching the offset of the sinc().
+      double x = (i - subsample_offset) / kKernelSize;
+      double window = kA0 - kA1 * cos(2.0 * M_PI * x) + kA2
+          * cos(4.0 * M_PI * x);
+
+      // Window the sinc() function and store at the correct offset.
+      kernel_storage_[i + offset_idx * kKernelSize] = sinc * window;
+    }
+  }
+}
+
+void SincResampler::Resample(float* destination, int frames) {
+  int remaining_frames = frames;
+
+  // Step (1) -- Prime the input buffer at the start of the input stream.
+  if (!buffer_primed_) {
+    read_cb_.Run(r0_, kBlockSize + kKernelSize / 2);
+    buffer_primed_ = true;
+  }
+
+  // Step (2) -- Resample!
+  while (remaining_frames) {
+    while (virtual_source_idx_ < kBlockSize) {
+      // |virtual_source_idx_| lies in between two kernel offsets so figure out
+      // what they are.
+      int source_idx = static_cast<int>(virtual_source_idx_);
+      double subsample_remainder = virtual_source_idx_ - source_idx;
+
+      double virtual_offset_idx = subsample_remainder * kKernelOffsetCount;
+      int offset_idx = static_cast<int>(virtual_offset_idx);
+
+      float* k1 = kernel_storage_.get() + offset_idx * kKernelSize;
+      float* k2 = k1 + kKernelSize;
+
+      // Initialize input pointer based on quantized |virtual_source_idx_|.
+      float* input_ptr = r1_ + source_idx;
+
+      // We'll compute "convolutions" for the two kernels which straddle
+      // |virtual_source_idx_|.
+      float sum1 = 0;
+      float sum2 = 0;
+
+      // Figure out how much to weight each kernel's "convolution".
+      double kernel_interpolation_factor = virtual_offset_idx - offset_idx;
+
+      // Generate a single output sample.
+      int n = kKernelSize;
+      float input;
+      // TODO(dalecurtis): For initial commit, I've ripped out all the SSE
+      // optimizations, these definitely need to go back in before release.
+      while (n--) {
+        input = *input_ptr++;
+        sum1 += input * *k1++;
+        sum2 += input * *k2++;
+      }
+
+      // Linearly interpolate the two "convolutions".
+      double result = (1.0 - kernel_interpolation_factor) * sum1
+          + kernel_interpolation_factor * sum2;
+
+      *destination++ = result;
+
+      // Advance the virtual index.
+      virtual_source_idx_ += io_sample_rate_ratio_;
+
+      if (!--remaining_frames)
+        return;
+    }
+
+    // Wrap back around to the start.
+    virtual_source_idx_ -= kBlockSize;
+
+    // Step (3) Copy r3_ to r1_ and r4_ to r2_.
+    // This wraps the last input frames back to the start of the buffer.
+    memcpy(r1_, r3_, sizeof(*input_buffer_.get()) * (kKernelSize / 2));
+    memcpy(r2_, r4_, sizeof(*input_buffer_.get()) * (kKernelSize / 2));
+
+    // Step (4)
+    // Refresh the buffer with more input.
+    read_cb_.Run(r5_, kBlockSize);
+  }
+}
+
+int SincResampler::ChunkSize() {
+  return kBlockSize / io_sample_rate_ratio_;
+}
+
+}  // namespace media

media/base/sinc_resampler.h

+// 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.
+
+#ifndef MEDIA_BASE_SINC_RESAMPLER_H_
+#define MEDIA_BASE_SINC_RESAMPLER_H_
+
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// SincResampler is a high-quality single-channel sample-rate converter.
+class MEDIA_EXPORT SincResampler {
+ public:
+  // Callback type for providing more data into the resampler.  Expects |frames|
+  // of data to be rendered into |destination|; zero padded if not enough frames
+  // are available to satisfy the request.
+  typedef base::Callback<void(float* destination, int frames)> ReadCB;
+
+  // Constructs a SincResampler with the specified |read_cb|, which is used to
+  // acquire audio data for resampling.  |io_sample_rate_ratio| is the ratio of
+  // input / output sample rates.
+  SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb);
+  virtual ~SincResampler();
+
+  // Resample |frames| of data from |read_cb_| into |destination|.
+  void Resample(float* destination, int frames);
+
+  // The maximum size in frames that guarantees Resample() will only make a
+  // single call to |read_cb_| for more data.
+  int ChunkSize();
+
+ private:
+  void InitializeKernel();
+
+  // The ratio of input / output sample rates.
+  double io_sample_rate_ratio_;
+
+  // An index on the source input buffer with sub-sample precision.  It must be
+  // double precision to avoid drift.
+  double virtual_source_idx_;
+
+  // The buffer is primed once at the very beginning of processing.
+  bool buffer_primed_;
+
+  // Source of data for resampling.
+  ReadCB read_cb_;
+
+  // Contains kKernelOffsetCount kernels back-to-back, each of size kKernelSize.
+  // The kernel offsets are sub-sample shifts of a windowed sinc shifted from
+  // 0.0 to 1.0 sample.
+  scoped_array<float> kernel_storage_;
+
+  // Data from the source is copied into this buffer for each processing pass.
+  scoped_array<float> input_buffer_;
+
+  // Pointers to the various regions inside |input_buffer_|.  See the diagram at
+  // the top of the .cc file for more information.
+  float* const r0_;
+  float* const r1_;
+  float* const r2_;
+  float* const r3_;
+  float* const r4_;
+  float* const r5_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_SINC_RESAMPLER_H_

media/media.gyp

@@ -189,6 +189,8 @@
         'base/ranges.h',
         'base/seekable_buffer.cc',
         'base/seekable_buffer.h',
+        'base/sinc_resampler.cc',
+        'base/sinc_resampler.h',
         'base/state_matrix.cc',
         'base/state_matrix.h',
         'base/stream_parser.cc',
@@ -686,6 +688,7 @@
         'base/ranges_unittest.cc',
         'base/run_all_unittests.cc',
         'base/seekable_buffer_unittest.cc',
+        'base/sinc_resampler_unittest.cc',
         'base/state_matrix_unittest.cc',
         'base/test_data_util.cc',
         'base/test_data_util.h',