blob: d4df9ffbfbc560926ecb8dcb17efc6d4d9f91fdd [file] [log] [blame]
// Copyright (c) 2015 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/interleaved_sinc_resampler.h"
#include <algorithm>
#include <cmath>
#include "base/logging.h"
namespace media {
namespace {
// The kernel size can be adjusted for quality (higher is better) at the
// expense of performance. Must be a multiple of 32.
const int kKernelSize = 32;
// The number of destination frames generated per processing pass. Affects
// how often and for how much InterleavedSincResampler calls back for input.
// Must be greater than kKernelSize.
const int 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.
const int kKernelOffsetCount = 32;
const int kKernelStorageSize = kKernelSize * (kKernelOffsetCount + 1);
// The size (in samples) of the internal buffer used by the resampler.
const int kBufferSize = kBlockSize + kKernelSize;
// The maximum numbers of buffer can be queued.
const int kMaximumPendingBuffers = 8;
} // namespace
InterleavedSincResampler::InterleavedSincResampler(double io_sample_rate_ratio,
int channel_count)
: io_sample_rate_ratio_(io_sample_rate_ratio),
virtual_source_idx_(0),
buffer_primed_(false),
channel_count_(channel_count),
frame_size_in_bytes_(sizeof(float) * channel_count_),
// Create buffers with a 16-byte alignment for possible optimizations.
kernel_storage_(static_cast<float*>(
base::AlignedAlloc(sizeof(float) * kKernelStorageSize, 16))),
input_buffer_(static_cast<float*>(
base::AlignedAlloc(frame_size_in_bytes_ * kBufferSize, 16))),
offset_in_frames_(0),
frames_resampled_(0),
frames_queued_(0),
// Setup various region pointers in the buffer (see diagram above).
r0_(input_buffer_.get() + kKernelSize / 2 * channel_count_),
r1_(input_buffer_.get()),
r2_(r0_),
r3_(r0_ + (kBlockSize - kKernelSize / 2) * channel_count_),
r4_(r0_ + kBlockSize * channel_count_),
r5_(r0_ + kKernelSize / 2 * channel_count_) {
// 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 * channel_count_);
// r5_ size correct and at the end of the buffer.
DCHECK_EQ(r5_ + kBlockSize * channel_count_,
r1_ + kBufferSize * channel_count_);
memset(kernel_storage_.get(), 0,
sizeof(*kernel_storage_.get()) * kKernelStorageSize);
memset(input_buffer_.get(), 0, frame_size_in_bytes_ * kBufferSize);
InitializeKernel();
}
void InterleavedSincResampler::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 InterleavedSincResampler::QueueBuffer(
const scoped_refptr<Buffer>& buffer) {
DCHECK(buffer);
DCHECK(CanQueueBuffer());
if (!pending_buffers_.empty() && pending_buffers_.back()->IsEndOfStream()) {
DCHECK(buffer->IsEndOfStream());
return;
}
if (!buffer->IsEndOfStream()) {
frames_queued_ += buffer->GetDataSize() / frame_size_in_bytes_;
}
pending_buffers_.push(buffer);
}
bool InterleavedSincResampler::Resample(float* destination, int frames) {
if (!HasEnoughData(frames)) {
return false;
}
int remaining_frames = frames;
// Step (1) -- Prime the input buffer at the start of the input stream.
if (!buffer_primed_) {
Read(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 * channel_count_;
// Figure out how much to weight each kernel's "convolution".
double kernel_interpolation_factor = virtual_offset_idx - offset_idx;
for (int i = 0; i < channel_count_; ++i) {
*destination++ =
Convolve(input_ptr + i, k1, k2, kernel_interpolation_factor);
}
// Advance the virtual index.
virtual_source_idx_ += io_sample_rate_ratio_;
if (!--remaining_frames) {
frames_resampled_ += frames;
return true;
}
}
// 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_, frame_size_in_bytes_ * (kKernelSize / 2));
memcpy(r2_, r4_, frame_size_in_bytes_ * (kKernelSize / 2));
// Step (4)
// Refresh the buffer with more input.
Read(r5_, kBlockSize);
}
NOTREACHED();
return false;
}
void InterleavedSincResampler::Flush() {
virtual_source_idx_ = 0;
buffer_primed_ = false;
memset(input_buffer_.get(), 0, frame_size_in_bytes_ * kBufferSize);
while (!pending_buffers_.empty()) {
pending_buffers_.pop();
}
offset_in_frames_ = 0;
frames_resampled_ = 0;
frames_queued_ = 0;
}
bool InterleavedSincResampler::CanQueueBuffer() const {
if (pending_buffers_.empty()) {
return true;
}
if (pending_buffers_.back()->IsEndOfStream()) {
return false;
}
return pending_buffers_.size() < kMaximumPendingBuffers;
}
bool InterleavedSincResampler::ReachedEOS() const {
if (pending_buffers_.empty() || !pending_buffers_.back()->IsEndOfStream()) {
return false;
}
return frames_resampled_ * io_sample_rate_ratio_ >= frames_queued_;
}
bool InterleavedSincResampler::HasEnoughData(int frames_to_resample) const {
// Always return true if EOS is seen, as in this case we will just fill 0.
if (!pending_buffers_.empty() && pending_buffers_.back()->IsEndOfStream()) {
return true;
}
// We have to decrease frames_queued_ down as the Read()s are always done in
// blocks of kBlockSize or kBufferSize. We have to ensure that there is buffer
// for an extra Read().
return (frames_resampled_ + frames_to_resample) * io_sample_rate_ratio_ <
frames_queued_ - kBufferSize;
}
void InterleavedSincResampler::Read(float* destination, int frames) {
while (frames > 0 && !pending_buffers_.empty()) {
scoped_refptr<Buffer> buffer = pending_buffers_.front();
if (buffer->IsEndOfStream()) {
// Zero fill the buffer after EOS has reached.
memset(destination, 0, frame_size_in_bytes_ * frames);
return;
}
// Copy the data over.
int frames_in_buffer = buffer->GetDataSize() / frame_size_in_bytes_;
int frames_to_copy = std::min(frames_in_buffer - offset_in_frames_, frames);
const uint8* source = buffer->GetData();
source += frame_size_in_bytes_ * offset_in_frames_;
memcpy(destination, source, frame_size_in_bytes_ * frames_to_copy);
offset_in_frames_ += frames_to_copy;
// Pop the first buffer if all its content has been read.
if (offset_in_frames_ == frames_in_buffer) {
offset_in_frames_ = 0;
pending_buffers_.pop();
}
frames -= frames_to_copy;
destination += frames_to_copy * channel_count_;
}
// Read should always be satisfied as otherwise Resample should return false
// to the caller directly.
DCHECK_EQ(frames, 0);
}
float InterleavedSincResampler::Convolve(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++;
input_ptr += channel_count_;
}
// Linearly interpolate the two "convolutions".
return (1.0 - kernel_interpolation_factor) * sum1 +
kernel_interpolation_factor * sum2;
}
} // namespace media