Reduce jitter from uneven SincResampler buffer size requests.

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/gtest_prod_util.h"
 #include "base/memory/aligned_memory.h"
 #include "base/memory/scoped_ptr.h"
 #include "build/build_config.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 // SincResampler is a high-quality single-channel sample-rate converter.
 class MEDIA_EXPORT SincResampler {
  public:
   enum {
     // The kernel size can be adjusted for quality (higher is better) at the
     // expense of performance.  Must be a multiple of 32.
     // 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,
+    // Default request size.  Affects how often and for how much SincResampler
+    // calls back for input.  Must be greater than kKernelSize.
+    kDefaultRequestSize = 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,
-
-    // The maximum number of samples that may be requested from the callback
-    // ahead of the current position in the stream.
-    kMaximumLookAheadSize = kBufferSize
   };
 
   // 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;
+  typedef base::Callback<void(int frames, float* destination)> 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);
+  // acquire audio data for resampling.  |io_sample_rate_ratio| is the ratio
+  // of input / output sample rates.  |request_frames| controls the size in
+  // frames of the buffer requested by each |read_cb| call.  The value must be
+  // greater than kKernelSize.  Specify kDefaultRequestSize if there are no
+  // request size constraints.
+  SincResampler(double io_sample_rate_ratio,
+                size_t request_frames,
+                const ReadCB& read_cb);
   virtual ~SincResampler();
 
   // Resample |frames| of data from |read_cb_| into |destination|.
-  void Resample(float* destination, int frames);
+  void Resample(int frames, float* destination);
 
   // The maximum size in frames that guarantees Resample() will only make a
   // single call to |read_cb_| for more data.
   int ChunkSize() const;
 
   // Flush all buffered data and reset internal indices.  Not thread safe, do
   // not call while Resample() is in progress.
   void Flush();
 
   // Update |io_sample_rate_ratio_|.  SetRatio() will cause a reconstruction of
   // the kernels used for resampling.  Not thread safe, do not call while
   // Resample() is in progress.
   void SetRatio(double io_sample_rate_ratio);
 
   float* get_kernel_for_testing() { return kernel_storage_.get(); }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(SincResamplerTest, Convolve);
   FRIEND_TEST_ALL_PREFIXES(SincResamplerTest, ConvolveBenchmark);
 
   void InitializeKernel();
+  void UpdateRegions(bool second_load);
 
   // Compute convolution of |k1| and |k2| over |input_ptr|, resultant sums are
   // linearly interpolated using |kernel_interpolation_factor|.  On x86, the
   // underlying implementation is chosen at run time based on SSE support.  On
   // ARM, NEON support is chosen at compile time based on compilation flags.
   static float Convolve_C(const float* input_ptr, const float* k1,
                           const float* k2, double kernel_interpolation_factor);
 #if defined(ARCH_CPU_X86_FAMILY)
   static float Convolve_SSE(const float* input_ptr, const float* k1,
                             const float* k2,
                             double kernel_interpolation_factor);
 #elif defined(ARCH_CPU_ARM_FAMILY) && defined(USE_NEON)
   static float Convolve_NEON(const float* input_ptr, const float* k1,
                              const float* k2,
                              double kernel_interpolation_factor);
 #endif
 
   // 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_;
+  const ReadCB read_cb_;
+
+  // The size (in samples) to request from each |read_cb_| execution.
+  const size_t request_frames_;
+
+  // The number of source frames processed per pass.
+  size_t block_size_;
+
+  // The size (in samples) of the internal buffer used by the resampler.
+  const size_t input_buffer_size_;
 
   // 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_ptr<float[], base::ScopedPtrAlignedFree> kernel_storage_;
   scoped_ptr<float[], base::ScopedPtrAlignedFree> kernel_pre_sinc_storage_;
   scoped_ptr<float[], base::ScopedPtrAlignedFree> kernel_window_storage_;
 
   // Data from the source is copied into this buffer for each processing pass.
   scoped_ptr<float[], base::ScopedPtrAlignedFree> input_buffer_;
 
   // Stores the runtime selection of which Convolve function to use.
 #if defined(ARCH_CPU_X86_FAMILY) && !defined(__SSE__)
   typedef float (*ConvolveProc)(const float*, const float*, const float*,
                                 double);
   const ConvolveProc convolve_proc_;
 #endif
 
   // 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* r0_;
   float* const r1_;
   float* const r2_;
-  float* const r3_;
-  float* const r4_;
-  float* const r5_;
+  float* r3_;
+  float* r4_;
 
   DISALLOW_COPY_AND_ASSIGN(SincResampler);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_SINC_RESAMPLER_H_