373 lines
14 KiB
C++
373 lines
14 KiB
C++
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/*
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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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// Modified from the Chromium original:
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// src/media/base/sinc_resampler.cc
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// Initial input buffer layout, dividing into regions r0_ to r4_ (note: r0_, r3_
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// and r4_ will move after the first load):
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//
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// |----------------|-----------------------------------------|----------------|
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//
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// request_frames_
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// <--------------------------------------------------------->
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// r0_ (during first load)
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//
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// kKernelSize / 2 kKernelSize / 2 kKernelSize / 2 kKernelSize / 2
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// <---------------> <---------------> <---------------> <--------------->
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// r1_ r2_ r3_ r4_
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//
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// block_size_ == r4_ - r2_
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// <--------------------------------------->
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//
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// request_frames_
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// <------------------ ... ----------------->
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// r0_ (during second load)
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//
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// On the second request r0_ slides to the right by kKernelSize / 2 and r3_, r4_
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// and block_size_ are reinitialized via step (3) in the algorithm below.
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//
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// These new regions remain constant until a Flush() occurs. While complicated,
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// this allows us to reduce jitter by always requesting the same amount from the
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// provided callback.
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//
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// The algorithm:
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//
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// 1) Allocate input_buffer of size: request_frames_ + kKernelSize; this ensures
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// there's enough room to read request_frames_ from the callback into region
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// r0_ (which will move between the first and subsequent passes).
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//
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// 2) Let r1_, r2_ each represent half the kernel centered around r0_:
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//
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// r0_ = input_buffer_ + kKernelSize / 2
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// r1_ = input_buffer_
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// r2_ = r0_
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//
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// r0_ is always request_frames_ in size. r1_, r2_ are kKernelSize / 2 in
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// size. r1_ must be zero initialized to avoid convolution with garbage (see
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// step (5) for why).
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//
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// 3) Let r3_, r4_ each represent half the kernel right aligned with the end of
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// r0_ and choose block_size_ as the distance in frames between r4_ and r2_:
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//
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// r3_ = r0_ + request_frames_ - kKernelSize
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// r4_ = r0_ + request_frames_ - kKernelSize / 2
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// block_size_ = r4_ - r2_ = request_frames_ - kKernelSize / 2
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//
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// 4) Consume request_frames_ frames into r0_.
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//
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// 5) Position kernel centered at start of r2_ and generate output frames until
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// the kernel is centered at the start of r4_ or we've finished generating
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// all the output frames.
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//
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// 6) Wrap left over data from the r3_ to r1_ and r4_ to r2_.
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//
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// 7) If we're on the second load, in order to avoid overwriting the frames we
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// just wrapped from r4_ we need to slide r0_ to the right by the size of
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// r4_, which is kKernelSize / 2:
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//
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// r0_ = r0_ + kKernelSize / 2 = input_buffer_ + kKernelSize
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//
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// r3_, r4_, and block_size_ then need to be reinitialized, so goto (3).
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//
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// 8) Else, if we're not on the second load, goto (4).
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//
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// Note: we're glossing over how the sub-sample handling works with
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// |virtual_source_idx_|, etc.
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// MSVC++ requires this to be set before any other includes to get M_PI.
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#define _USE_MATH_DEFINES
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#include "webrtc/common_audio/resampler/sinc_resampler.h"
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#include <assert.h>
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#include <math.h>
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#include <string.h>
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#include <limits>
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#include "webrtc/system_wrappers/include/cpu_features_wrapper.h"
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#include "webrtc/typedefs.h"
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namespace webrtc {
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namespace {
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double SincScaleFactor(double io_ratio) {
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// |sinc_scale_factor| is basically the normalized cutoff frequency of the
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// low-pass filter.
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double sinc_scale_factor = io_ratio > 1.0 ? 1.0 / io_ratio : 1.0;
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// The sinc function is an idealized brick-wall filter, but since we're
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// windowing it the transition from pass to stop does not happen right away.
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// So we should adjust the low pass filter cutoff slightly downward to avoid
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// some aliasing at the very high-end.
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// TODO(crogers): this value is empirical and to be more exact should vary
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// depending on kKernelSize.
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sinc_scale_factor *= 0.9;
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return sinc_scale_factor;
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}
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} // namespace
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// If we know the minimum architecture at compile time, avoid CPU detection.
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#if defined(WEBRTC_ARCH_X86_FAMILY)
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#if defined(__SSE2__)
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#define CONVOLVE_FUNC Convolve_SSE
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void SincResampler::InitializeCPUSpecificFeatures() {}
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#else
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// x86 CPU detection required. Function will be set by
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// InitializeCPUSpecificFeatures().
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// TODO(dalecurtis): Once Chrome moves to an SSE baseline this can be removed.
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#define CONVOLVE_FUNC convolve_proc_
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void SincResampler::InitializeCPUSpecificFeatures() {
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convolve_proc_ = WebRtc_GetCPUInfo(kSSE2) ? Convolve_SSE : Convolve_C;
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}
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#endif
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#elif defined(WEBRTC_HAS_NEON)
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#define CONVOLVE_FUNC Convolve_NEON
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void SincResampler::InitializeCPUSpecificFeatures() {}
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#else
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// Unknown architecture.
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#define CONVOLVE_FUNC Convolve_C
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void SincResampler::InitializeCPUSpecificFeatures() {}
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#endif
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SincResampler::SincResampler(double io_sample_rate_ratio,
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size_t request_frames,
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SincResamplerCallback* read_cb)
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: io_sample_rate_ratio_(io_sample_rate_ratio),
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read_cb_(read_cb),
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request_frames_(request_frames),
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input_buffer_size_(request_frames_ + kKernelSize),
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// Create input buffers with a 16-byte alignment for SSE optimizations.
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kernel_storage_(static_cast<float*>(
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AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))),
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kernel_pre_sinc_storage_(static_cast<float*>(
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AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))),
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kernel_window_storage_(static_cast<float*>(
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AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))),
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input_buffer_(static_cast<float*>(
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AlignedMalloc(sizeof(float) * input_buffer_size_, 16))),
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#if defined(WEBRTC_CPU_DETECTION)
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convolve_proc_(NULL),
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#endif
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r1_(input_buffer_.get()),
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r2_(input_buffer_.get() + kKernelSize / 2) {
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#if defined(WEBRTC_CPU_DETECTION)
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InitializeCPUSpecificFeatures();
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assert(convolve_proc_);
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#endif
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assert(request_frames_ > 0);
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Flush();
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assert(block_size_ > kKernelSize);
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memset(kernel_storage_.get(), 0,
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sizeof(*kernel_storage_.get()) * kKernelStorageSize);
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memset(kernel_pre_sinc_storage_.get(), 0,
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sizeof(*kernel_pre_sinc_storage_.get()) * kKernelStorageSize);
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memset(kernel_window_storage_.get(), 0,
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sizeof(*kernel_window_storage_.get()) * kKernelStorageSize);
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InitializeKernel();
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}
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SincResampler::~SincResampler() {}
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void SincResampler::UpdateRegions(bool second_load) {
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// Setup various region pointers in the buffer (see diagram above). If we're
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// on the second load we need to slide r0_ to the right by kKernelSize / 2.
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r0_ = input_buffer_.get() + (second_load ? kKernelSize : kKernelSize / 2);
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r3_ = r0_ + request_frames_ - kKernelSize;
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r4_ = r0_ + request_frames_ - kKernelSize / 2;
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block_size_ = r4_ - r2_;
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// r1_ at the beginning of the buffer.
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assert(r1_ == input_buffer_.get());
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// r1_ left of r2_, r4_ left of r3_ and size correct.
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assert(r2_ - r1_ == r4_ - r3_);
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// r2_ left of r3.
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assert(r2_ < r3_);
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}
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void SincResampler::InitializeKernel() {
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// Blackman window parameters.
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static const double kAlpha = 0.16;
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static const double kA0 = 0.5 * (1.0 - kAlpha);
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static const double kA1 = 0.5;
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static const double kA2 = 0.5 * kAlpha;
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// Generates a set of windowed sinc() kernels.
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// We generate a range of sub-sample offsets from 0.0 to 1.0.
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const double sinc_scale_factor = SincScaleFactor(io_sample_rate_ratio_);
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for (size_t offset_idx = 0; offset_idx <= kKernelOffsetCount; ++offset_idx) {
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const float subsample_offset =
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static_cast<float>(offset_idx) / kKernelOffsetCount;
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for (size_t i = 0; i < kKernelSize; ++i) {
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const size_t idx = i + offset_idx * kKernelSize;
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const float pre_sinc = static_cast<float>(M_PI *
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(static_cast<int>(i) - static_cast<int>(kKernelSize / 2) -
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subsample_offset));
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kernel_pre_sinc_storage_[idx] = pre_sinc;
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// Compute Blackman window, matching the offset of the sinc().
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const float x = (i - subsample_offset) / kKernelSize;
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const float window = static_cast<float>(kA0 - kA1 * cos(2.0 * M_PI * x) +
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kA2 * cos(4.0 * M_PI * x));
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kernel_window_storage_[idx] = window;
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// Compute the sinc with offset, then window the sinc() function and store
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// at the correct offset.
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kernel_storage_[idx] = static_cast<float>(window *
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((pre_sinc == 0) ?
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sinc_scale_factor :
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(sin(sinc_scale_factor * pre_sinc) / pre_sinc)));
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}
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}
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}
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void SincResampler::SetRatio(double io_sample_rate_ratio) {
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if (fabs(io_sample_rate_ratio_ - io_sample_rate_ratio) <
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std::numeric_limits<double>::epsilon()) {
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return;
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}
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io_sample_rate_ratio_ = io_sample_rate_ratio;
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// Optimize reinitialization by reusing values which are independent of
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// |sinc_scale_factor|. Provides a 3x speedup.
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const double sinc_scale_factor = SincScaleFactor(io_sample_rate_ratio_);
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for (size_t offset_idx = 0; offset_idx <= kKernelOffsetCount; ++offset_idx) {
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for (size_t i = 0; i < kKernelSize; ++i) {
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const size_t idx = i + offset_idx * kKernelSize;
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const float window = kernel_window_storage_[idx];
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const float pre_sinc = kernel_pre_sinc_storage_[idx];
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kernel_storage_[idx] = static_cast<float>(window *
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((pre_sinc == 0) ?
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sinc_scale_factor :
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(sin(sinc_scale_factor * pre_sinc) / pre_sinc)));
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}
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}
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}
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void SincResampler::Resample(size_t frames, float* destination) {
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size_t remaining_frames = frames;
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// Step (1) -- Prime the input buffer at the start of the input stream.
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if (!buffer_primed_ && remaining_frames) {
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read_cb_->Run(request_frames_, r0_);
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buffer_primed_ = true;
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}
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// Step (2) -- Resample! const what we can outside of the loop for speed. It
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// actually has an impact on ARM performance. See inner loop comment below.
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const double current_io_ratio = io_sample_rate_ratio_;
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const float* const kernel_ptr = kernel_storage_.get();
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while (remaining_frames) {
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// |i| may be negative if the last Resample() call ended on an iteration
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// that put |virtual_source_idx_| over the limit.
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//
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// Note: The loop construct here can severely impact performance on ARM
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// or when built with clang. See https://codereview.chromium.org/18566009/
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for (int i = static_cast<int>(
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ceil((block_size_ - virtual_source_idx_) / current_io_ratio));
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i > 0; --i) {
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assert(virtual_source_idx_ < block_size_);
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// |virtual_source_idx_| lies in between two kernel offsets so figure out
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// what they are.
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const int source_idx = static_cast<int>(virtual_source_idx_);
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const double subsample_remainder = virtual_source_idx_ - source_idx;
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const double virtual_offset_idx =
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subsample_remainder * kKernelOffsetCount;
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const int offset_idx = static_cast<int>(virtual_offset_idx);
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// We'll compute "convolutions" for the two kernels which straddle
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// |virtual_source_idx_|.
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const float* const k1 = kernel_ptr + offset_idx * kKernelSize;
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const float* const k2 = k1 + kKernelSize;
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// Ensure |k1|, |k2| are 16-byte aligned for SIMD usage. Should always be
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// true so long as kKernelSize is a multiple of 16.
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assert(0u == (reinterpret_cast<uintptr_t>(k1) & 0x0F));
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assert(0u == (reinterpret_cast<uintptr_t>(k2) & 0x0F));
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// Initialize input pointer based on quantized |virtual_source_idx_|.
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const float* const input_ptr = r1_ + source_idx;
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// Figure out how much to weight each kernel's "convolution".
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const double kernel_interpolation_factor =
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virtual_offset_idx - offset_idx;
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*destination++ = CONVOLVE_FUNC(
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input_ptr, k1, k2, kernel_interpolation_factor);
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// Advance the virtual index.
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virtual_source_idx_ += current_io_ratio;
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if (!--remaining_frames)
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return;
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}
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// Wrap back around to the start.
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virtual_source_idx_ -= block_size_;
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// Step (3) -- Copy r3_, r4_ to r1_, r2_.
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// This wraps the last input frames back to the start of the buffer.
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memcpy(r1_, r3_, sizeof(*input_buffer_.get()) * kKernelSize);
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// Step (4) -- Reinitialize regions if necessary.
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if (r0_ == r2_)
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UpdateRegions(true);
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// Step (5) -- Refresh the buffer with more input.
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read_cb_->Run(request_frames_, r0_);
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}
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}
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#undef CONVOLVE_FUNC
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size_t SincResampler::ChunkSize() const {
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return static_cast<size_t>(block_size_ / io_sample_rate_ratio_);
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}
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void SincResampler::Flush() {
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virtual_source_idx_ = 0;
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buffer_primed_ = false;
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memset(input_buffer_.get(), 0,
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sizeof(*input_buffer_.get()) * input_buffer_size_);
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UpdateRegions(false);
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}
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float SincResampler::Convolve_C(const float* input_ptr, const float* k1,
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const float* k2,
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||
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|
double kernel_interpolation_factor) {
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float sum1 = 0;
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||
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|
float sum2 = 0;
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||
|
|
|
||
|
|
// Generate a single output sample. Unrolling this loop hurt performance in
|
||
|
|
// local testing.
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||
|
|
size_t n = kKernelSize;
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||
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|
while (n--) {
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||
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|
sum1 += *input_ptr * *k1++;
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||
|
|
sum2 += *input_ptr++ * *k2++;
|
||
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|
}
|
||
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|
|
||
|
|
// Linearly interpolate the two "convolutions".
|
||
|
|
return static_cast<float>((1.0 - kernel_interpolation_factor) * sum1 +
|
||
|
|
kernel_interpolation_factor * sum2);
|
||
|
|
}
|
||
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||
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|
} // namespace webrtc
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