blob: d104a1c7df1980f8dc1708c9c7389f666138132c [file] [log] [blame]
// 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.
#include "media/base/sinc_resampler.h"
#include <cmath>
#include "base/cpu.h"
#include "base/logging.h"
#include "build/build_config.h"
#if defined(ARCH_CPU_X86_FAMILY) && defined(__SSE__)
#include <xmmintrin.h>
#endif
#if defined(ARCH_CPU_ARM_FAMILY) && defined(USE_NEON)
#include <arm_neon.h>
#endif
namespace media {
namespace {
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,
// 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
};
} // namespace
const int SincResampler::kMaximumLookAheadSize = kBufferSize;
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),
// Create input buffers with a 16-byte alignment for SSE optimizations.
kernel_storage_(static_cast<float*>(
base::AlignedAlloc(sizeof(float) * kKernelStorageSize, 16))),
input_buffer_(static_cast<float*>(
base::AlignedAlloc(sizeof(float) * kBufferSize, 16))),
// 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);
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_.get()[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);
// 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;
// Initialize input pointer based on quantized |virtual_source_idx_|.
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;
*destination++ = Convolve(
input_ptr, k1, k2, kernel_interpolation_factor);
// 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_;
}
void SincResampler::Flush() {
virtual_source_idx_ = 0;
buffer_primed_ = false;
memset(input_buffer_.get(), 0, sizeof(*input_buffer_.get()) * kBufferSize);
}
float SincResampler::Convolve(const float* input_ptr, const float* k1,
const float* k2,
double kernel_interpolation_factor) {
// Rely on function level static initialization to keep ConvolveProc selection
// thread safe.
typedef float (*ConvolveProc)(const float* src, const float* k1,
const float* k2,
double kernel_interpolation_factor);
#if defined(ARCH_CPU_X86_FAMILY) && defined(__SSE__)
static const ConvolveProc kConvolveProc =
base::CPU().has_sse() ? Convolve_SSE : Convolve_C;
#elif defined(ARCH_CPU_ARM_FAMILY) && defined(USE_NEON)
static const ConvolveProc kConvolveProc = Convolve_NEON;
#else
static const ConvolveProc kConvolveProc = Convolve_C;
#endif
return kConvolveProc(input_ptr, k1, k2, kernel_interpolation_factor);
}
float SincResampler::Convolve_C(const float* input_ptr, const float* k1,
const float* k2,
double kernel_interpolation_factor) {
float sum1 = 0;
float sum2 = 0;
// Generate a single output sample. Unrolling this loop hurt performance in
// local testing.
int n = kKernelSize;
while (n--) {
sum1 += *input_ptr * *k1++;
sum2 += *input_ptr++ * *k2++;
}
// Linearly interpolate the two "convolutions".
return (1.0 - kernel_interpolation_factor) * sum1
+ kernel_interpolation_factor * sum2;
}
#if defined(ARCH_CPU_X86_FAMILY) && defined(__SSE__)
float SincResampler::Convolve_SSE(const float* input_ptr, const float* k1,
const float* k2,
double kernel_interpolation_factor) {
// Ensure |k1|, |k2| are 16-byte aligned for SSE usage. Should always be true
// so long as kKernelSize is a multiple of 16.
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(k1) & 0x0F);
DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(k2) & 0x0F);
__m128 m_input;
__m128 m_sums1 = _mm_setzero_ps();
__m128 m_sums2 = _mm_setzero_ps();
// Based on |input_ptr| alignment, we need to use loadu or load. Unrolling
// these loops hurt performance in local testing.
if (reinterpret_cast<uintptr_t>(input_ptr) & 0x0F) {
for (int i = 0; i < kKernelSize; i += 4) {
m_input = _mm_loadu_ps(input_ptr + i);
m_sums1 = _mm_add_ps(m_sums1, _mm_mul_ps(m_input, _mm_load_ps(k1 + i)));
m_sums2 = _mm_add_ps(m_sums2, _mm_mul_ps(m_input, _mm_load_ps(k2 + i)));
}
} else {
for (int i = 0; i < kKernelSize; i += 4) {
m_input = _mm_load_ps(input_ptr + i);
m_sums1 = _mm_add_ps(m_sums1, _mm_mul_ps(m_input, _mm_load_ps(k1 + i)));
m_sums2 = _mm_add_ps(m_sums2, _mm_mul_ps(m_input, _mm_load_ps(k2 + i)));
}
}
// Linearly interpolate the two "convolutions".
m_sums1 = _mm_mul_ps(m_sums1, _mm_set_ps1(1.0 - kernel_interpolation_factor));
m_sums2 = _mm_mul_ps(m_sums2, _mm_set_ps1(kernel_interpolation_factor));
m_sums1 = _mm_add_ps(m_sums1, m_sums2);
// Sum components together.
float result;
m_sums2 = _mm_add_ps(_mm_movehl_ps(m_sums1, m_sums1), m_sums1);
_mm_store_ss(&result, _mm_add_ss(m_sums2, _mm_shuffle_ps(
m_sums2, m_sums2, 1)));
return result;
}
#endif
#if defined(ARCH_CPU_ARM_FAMILY) && defined(USE_NEON)
float SincResampler::Convolve_NEON(const float* input_ptr, const float* k1,
const float* k2,
double kernel_interpolation_factor) {
float32x4_t m_input;
float32x4_t m_sums1 = vmovq_n_f32(0);
float32x4_t m_sums2 = vmovq_n_f32(0);
const float* upper = input_ptr + kKernelSize;
for (; input_ptr < upper; ) {
m_input = vld1q_f32(input_ptr);
input_ptr += 4;
m_sums1 = vmlaq_f32(m_sums1, m_input, vld1q_f32(k1));
k1 += 4;
m_sums2 = vmlaq_f32(m_sums2, m_input, vld1q_f32(k2));
k2 += 4;
}
// Linearly interpolate the two "convolutions".
m_sums1 = vmlaq_f32(
vmulq_f32(m_sums1, vmovq_n_f32(1.0 - kernel_interpolation_factor)),
m_sums2, vmovq_n_f32(kernel_interpolation_factor));
// Sum components together.
float32x2_t m_half = vadd_f32(vget_high_f32(m_sums1), vget_low_f32(m_sums1));
return vget_lane_f32(vpadd_f32(m_half, m_half), 0);
}
#endif
} // namespace media