Add SincResampler ported from WebKit.

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_