Reduce jitter from uneven SincResampler buffer size requests.

Ensures all buffer requests are for the same size.  Reduces jitter
by allowing clients with specific buffer size requirements to avoid
overreading.

BUG=none
TEST=media_unittests.
R=crogers@google.com, henrika@chromium.org, sergeyu@chromium.org

Review URL: https://codereview.chromium.org/14189035

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@199032 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 27 insertions, 21 deletions

diff --git a/media/base/sinc_resampler.h b/media/base/sinc_resampler.h
index 3ccb85c..84695b1 100644
--- a/media/base/sinc_resampler.h
+++ b/media/base/sinc_resampler.h
@@ -23,38 +23,35 @@ class MEDIA_EXPORT SincResampler {
     // 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.
@@ -76,6 +73,7 @@ class MEDIA_EXPORT SincResampler {
   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
@@ -104,7 +102,16 @@ class MEDIA_EXPORT SincResampler {
   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
@@ -125,12 +132,11 @@ class MEDIA_EXPORT SincResampler {
 
   // 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);
 };