Index: media/base/sinc_resampler.cc |
diff --git a/media/base/sinc_resampler.cc b/media/base/sinc_resampler.cc |
index 6bce67a3e7e85252240fad089711a2f769be6d14..98d6b7462d6aafaef4e1dc9d79882441f3d48ac4 100644 |
--- a/media/base/sinc_resampler.cc |
+++ b/media/base/sinc_resampler.cc |
@@ -2,31 +2,46 @@ |
// 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_): |
+// Initial input buffer layout, dividing into regions r0_ to r4_: |
// |
// |----------------|-----------------------------------------|----------------| |
// |
-// kBlockSize + kKernelSize / 2 |
+// 1st request: request_size_ |
// <---------------------------------------------------------> |
// r0_ |
// |
+// block_size_ = request_size_ - kKernelSize / 2 |
+// <---------------------------------------> |
+// |
// kKernelSize / 2 kKernelSize / 2 kKernelSize / 2 kKernelSize / 2 |
// <---------------> <---------------> <---------------> <---------------> |
// r1_ r2_ r3_ r4_ |
// |
-// kBlockSize |
-// <---------------------------------------> |
-// r5_ |
+// On the second request, block_size_ increases to request_size_ while r0_, r3_, |
+// and r4_ slide to the right by kKernelSize / 2: |
+// |
+// |----------------|-----------------------------------------|----------------| |
+// |
+// 2nd request: request_size_ |
+// <------------------ ... -----------------> |
+// |
+// block_size_ = request_size_ |
+// <---------------- ... ------------------> |
+// |
+// These new regions remain constant until a Flush() occurs. While complicated, |
+// this allows us to reduce jitter by always requesting the same amount from the |
+// provided callback. |
// |
// The algorithm: |
// |
-// 1) Consume input frames into r0_ (r1_ is zero-initialized). |
+// 1) Consume |request_size_| 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. |
+// 3) Copy r3_ to r1_, r4_ to r2_. |
+// 4) If we're on the second load, set block_size_ equal to request_size_ |
+// and reinitialize r0_, r3_, and r4_ appropriately. |
+// 5) Goto (1). |
// |
// Note: we're glossing over how the sub-sample handling works with |
// |virtual_source_idx_|, etc. |
@@ -64,11 +79,12 @@ static double SincScaleFactor(double io_ratio) { |
return sinc_scale_factor; |
} |
-SincResampler::SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb) |
+SincResampler::SincResampler(double io_sample_rate_ratio, size_t request_size, |
+ const ReadCB& read_cb) |
: io_sample_rate_ratio_(io_sample_rate_ratio), |
- virtual_source_idx_(0), |
- buffer_primed_(false), |
read_cb_(read_cb), |
+ request_size_(request_size), |
+ input_buffer_size_(request_size_ + kKernelSize), |
// Create input buffers with a 16-byte alignment for SSE optimizations. |
kernel_storage_(static_cast<float*>( |
base::AlignedAlloc(sizeof(float) * kKernelStorageSize, 16))), |
@@ -77,36 +93,14 @@ SincResampler::SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb) |
kernel_window_storage_(static_cast<float*>( |
base::AlignedAlloc(sizeof(float) * kKernelStorageSize, 16))), |
input_buffer_(static_cast<float*>( |
- base::AlignedAlloc(sizeof(float) * kBufferSize, 16))), |
+ base::AlignedAlloc(sizeof(float) * input_buffer_size_, 16))), |
#if defined(ARCH_CPU_X86_FAMILY) && !defined(__SSE__) |
convolve_proc_(base::CPU().has_sse() ? Convolve_SSE : Convolve_C), |
#endif |
- // 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) { |
- // Ensure kKernelSize is a multiple of 32 for easy SSE optimizations; causes |
- // r0_ and r5_ (used for input) to always be 16-byte aligned by virtue of |
- // input_buffer_ being 16-byte aligned. |
- DCHECK_EQ(kKernelSize % 32, 0) << "kKernelSize must be a multiple of 32!"; |
- 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); |
+ reinitialize_regions_(false) { |
+ Flush(); |
+ CHECK_GT(block_size_, static_cast<size_t>(kKernelSize)) |
henrika (OOO until Aug 14)
2013/04/27 19:43:40
Thanks :-)
|
+ << "block_size must be greater than kKernelSize!"; |
memset(kernel_storage_.get(), 0, |
sizeof(*kernel_storage_.get()) * kKernelStorageSize); |
@@ -114,13 +108,28 @@ SincResampler::SincResampler(double io_sample_rate_ratio, const ReadCB& read_cb) |
sizeof(*kernel_pre_sinc_storage_.get()) * kKernelStorageSize); |
memset(kernel_window_storage_.get(), 0, |
sizeof(*kernel_window_storage_.get()) * kKernelStorageSize); |
- memset(input_buffer_.get(), 0, sizeof(*input_buffer_.get()) * kBufferSize); |
InitializeKernel(); |
} |
SincResampler::~SincResampler() {} |
+void SincResampler::UpdateRegions() { |
+ // Setup various region pointers in the buffer (see diagram above). |
+ r1_ = input_buffer_.get(); |
+ r2_ = input_buffer_.get() + kKernelSize / 2; |
+ r0_ = reinitialize_regions_ ? input_buffer_.get() + kKernelSize : r2_; |
+ r3_ = r2_ + block_size_ - kKernelSize / 2; |
+ r4_ = r2_ + block_size_; |
+ |
+ // r1_ at the beginning of the buffer. |
+ CHECK_EQ(r1_, input_buffer_.get()); |
+ // r1_ left of r2_, r4_ left of r3_ and size correct. |
+ CHECK_EQ(r2_ - r1_, r4_ - r3_); |
+ // r2_ left of r3. |
+ CHECK_LT(r2_, r3_); |
+} |
+ |
void SincResampler::InitializeKernel() { |
// Blackman window parameters. |
static const double kAlpha = 0.16; |
@@ -206,25 +215,27 @@ void SincResampler::Resample(float* destination, int frames) { |
// Step (1) -- Prime the input buffer at the start of the input stream. |
if (!buffer_primed_) { |
- read_cb_.Run(r0_, kBlockSize + kKernelSize / 2); |
+ read_cb_.Run(r0_, request_size_); |
buffer_primed_ = true; |
+ reinitialize_regions_ = true; |
} |
// Step (2) -- Resample! |
while (remaining_frames) { |
- while (virtual_source_idx_ < kBlockSize) { |
+ while (virtual_source_idx_ < block_size_) { |
// |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; |
+ const int source_idx = virtual_source_idx_; |
+ const double subsample_remainder = virtual_source_idx_ - source_idx; |
- double virtual_offset_idx = subsample_remainder * kKernelOffsetCount; |
- int offset_idx = static_cast<int>(virtual_offset_idx); |
+ const double virtual_offset_idx = |
+ subsample_remainder * kKernelOffsetCount; |
+ const int offset_idx = virtual_offset_idx; |
// We'll compute "convolutions" for the two kernels which straddle |
// |virtual_source_idx_|. |
- float* k1 = kernel_storage_.get() + offset_idx * kKernelSize; |
- float* k2 = k1 + kKernelSize; |
+ const float* k1 = kernel_storage_.get() + offset_idx * kKernelSize; |
+ const float* k2 = k1 + kKernelSize; |
// Ensure |k1|, |k2| are 16-byte aligned for SIMD usage. Should always be |
// true so long as kKernelSize is a multiple of 16. |
@@ -232,10 +243,11 @@ void SincResampler::Resample(float* destination, int frames) { |
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(k2) & 0x0F); |
// Initialize input pointer based on quantized |virtual_source_idx_|. |
- float* input_ptr = r1_ + source_idx; |
+ const float* input_ptr = r1_ + source_idx; |
// Figure out how much to weight each kernel's "convolution". |
- double kernel_interpolation_factor = virtual_offset_idx - offset_idx; |
+ const double kernel_interpolation_factor = |
+ virtual_offset_idx - offset_idx; |
*destination++ = CONVOLVE_FUNC( |
input_ptr, k1, k2, kernel_interpolation_factor); |
@@ -247,29 +259,39 @@ void SincResampler::Resample(float* destination, int frames) { |
} |
// Wrap back around to the start. |
- virtual_source_idx_ -= kBlockSize; |
+ virtual_source_idx_ -= block_size_; |
- // Step (3) Copy r3_ to r1_ and r4_ to r2_. |
+ // Step (3) -- Copy r3_, r4_ to r1_, 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)); |
+ memcpy(r1_, r3_, sizeof(*input_buffer_.get()) * kKernelSize); |
- // Step (4) |
- // Refresh the buffer with more input. |
- read_cb_.Run(r5_, kBlockSize); |
+ // Step (4) -- Reinitialize regions if necessary. |
+ if (reinitialize_regions_) { |
+ block_size_ = request_size_; |
+ UpdateRegions(); |
+ reinitialize_regions_ = false; |
+ } |
+ |
+ // Step (5) -- Refresh the buffer with more input. |
+ read_cb_.Run(r0_, request_size_); |
} |
} |
#undef CONVOLVE_FUNC |
int SincResampler::ChunkSize() const { |
- return kBlockSize / io_sample_rate_ratio_; |
+ return block_size_ / io_sample_rate_ratio_; |
} |
void SincResampler::Flush() { |
virtual_source_idx_ = 0; |
buffer_primed_ = false; |
- memset(input_buffer_.get(), 0, sizeof(*input_buffer_.get()) * kBufferSize); |
+ memset(input_buffer_.get(), 0, |
+ sizeof(*input_buffer_.get()) * input_buffer_size_); |
+ |
+ block_size_ = request_size_ - kKernelSize / 2; |
+ reinitialize_regions_ = false; |
+ UpdateRegions(); |
} |
float SincResampler::Convolve_C(const float* input_ptr, const float* k1, |