1 /* 2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 // Modified from the Chromium original: 12 // src/media/base/sinc_resampler.cc 13 14 // Initial input buffer layout, dividing into regions r0_ to r4_ (note: r0_, r3_ 15 // and r4_ will move after the first load): 16 // 17 // |----------------|-----------------------------------------|----------------| 18 // 19 // request_frames_ 20 // <---------------------------------------------------------> 21 // r0_ (during first load) 22 // 23 // kKernelSize / 2 kKernelSize / 2 kKernelSize / 2 kKernelSize / 2 24 // <---------------> <---------------> <---------------> <---------------> 25 // r1_ r2_ r3_ r4_ 26 // 27 // block_size_ == r4_ - r2_ 28 // <---------------------------------------> 29 // 30 // request_frames_ 31 // <------------------ ... -----------------> 32 // r0_ (during second load) 33 // 34 // On the second request r0_ slides to the right by kKernelSize / 2 and r3_, r4_ 35 // and block_size_ are reinitialized via step (3) in the algorithm below. 36 // 37 // These new regions remain constant until a Flush() occurs. While complicated, 38 // this allows us to reduce jitter by always requesting the same amount from the 39 // provided callback. 40 // 41 // The algorithm: 42 // 43 // 1) Allocate input_buffer of size: request_frames_ + kKernelSize; this ensures 44 // there's enough room to read request_frames_ from the callback into region 45 // r0_ (which will move between the first and subsequent passes). 46 // 47 // 2) Let r1_, r2_ each represent half the kernel centered around r0_: 48 // 49 // r0_ = input_buffer_ + kKernelSize / 2 50 // r1_ = input_buffer_ 51 // r2_ = r0_ 52 // 53 // r0_ is always request_frames_ in size. r1_, r2_ are kKernelSize / 2 in 54 // size. r1_ must be zero initialized to avoid convolution with garbage (see 55 // step (5) for why). 56 // 57 // 3) Let r3_, r4_ each represent half the kernel right aligned with the end of 58 // r0_ and choose block_size_ as the distance in frames between r4_ and r2_: 59 // 60 // r3_ = r0_ + request_frames_ - kKernelSize 61 // r4_ = r0_ + request_frames_ - kKernelSize / 2 62 // block_size_ = r4_ - r2_ = request_frames_ - kKernelSize / 2 63 // 64 // 4) Consume request_frames_ frames into r0_. 65 // 66 // 5) Position kernel centered at start of r2_ and generate output frames until 67 // the kernel is centered at the start of r4_ or we've finished generating 68 // all the output frames. 69 // 70 // 6) Wrap left over data from the r3_ to r1_ and r4_ to r2_. 71 // 72 // 7) If we're on the second load, in order to avoid overwriting the frames we 73 // just wrapped from r4_ we need to slide r0_ to the right by the size of 74 // r4_, which is kKernelSize / 2: 75 // 76 // r0_ = r0_ + kKernelSize / 2 = input_buffer_ + kKernelSize 77 // 78 // r3_, r4_, and block_size_ then need to be reinitialized, so goto (3). 79 // 80 // 8) Else, if we're not on the second load, goto (4). 81 // 82 // Note: we're glossing over how the sub-sample handling works with 83 // |virtual_source_idx_|, etc. 84 85 // MSVC++ requires this to be set before any other includes to get M_PI. 86 #define _USE_MATH_DEFINES 87 88 #include "webrtc/common_audio/resampler/sinc_resampler.h" 89 #include "webrtc/system_wrappers/interface/compile_assert.h" 90 #include "webrtc/system_wrappers/interface/cpu_features_wrapper.h" 91 #include "webrtc/typedefs.h" 92 93 #include <assert.h> 94 #include <math.h> 95 #include <string.h> 96 97 #include <limits> 98 99 namespace webrtc { 100 101 static double SincScaleFactor(double io_ratio) { 102 // |sinc_scale_factor| is basically the normalized cutoff frequency of the 103 // low-pass filter. 104 double sinc_scale_factor = io_ratio > 1.0 ? 1.0 / io_ratio : 1.0; 105 106 // The sinc function is an idealized brick-wall filter, but since we're 107 // windowing it the transition from pass to stop does not happen right away. 108 // So we should adjust the low pass filter cutoff slightly downward to avoid 109 // some aliasing at the very high-end. 110 // TODO(crogers): this value is empirical and to be more exact should vary 111 // depending on kKernelSize. 112 sinc_scale_factor *= 0.9; 113 114 return sinc_scale_factor; 115 } 116 117 // If we know the minimum architecture at compile time, avoid CPU detection. 118 #if defined(WEBRTC_ARCH_X86_FAMILY) 119 #if defined(__SSE2__) 120 #define CONVOLVE_FUNC Convolve_SSE 121 void SincResampler::InitializeCPUSpecificFeatures() {} 122 #else 123 // x86 CPU detection required. Function will be set by 124 // InitializeCPUSpecificFeatures(). 125 // TODO(dalecurtis): Once Chrome moves to an SSE baseline this can be removed. 126 #define CONVOLVE_FUNC convolve_proc_ 127 128 void SincResampler::InitializeCPUSpecificFeatures() { 129 convolve_proc_ = WebRtc_GetCPUInfo(kSSE2) ? Convolve_SSE : Convolve_C; 130 } 131 #endif 132 #elif defined(WEBRTC_ARCH_ARM_V7) 133 #if defined(WEBRTC_ARCH_ARM_NEON) 134 #define CONVOLVE_FUNC Convolve_NEON 135 void SincResampler::InitializeCPUSpecificFeatures() {} 136 #else 137 // ARM CPU detection required. Function will be set by 138 // InitializeCPUSpecificFeatures(). 139 #define CONVOLVE_FUNC convolve_proc_ 140 141 void SincResampler::InitializeCPUSpecificFeatures() { 142 convolve_proc_ = WebRtc_GetCPUFeaturesARM() & kCPUFeatureNEON ? 143 Convolve_NEON : Convolve_C; 144 } 145 #endif 146 #else 147 // Unknown architecture. 148 #define CONVOLVE_FUNC Convolve_C 149 void SincResampler::InitializeCPUSpecificFeatures() {} 150 #endif 151 152 SincResampler::SincResampler(double io_sample_rate_ratio, 153 int request_frames, 154 SincResamplerCallback* read_cb) 155 : io_sample_rate_ratio_(io_sample_rate_ratio), 156 read_cb_(read_cb), 157 request_frames_(request_frames), 158 input_buffer_size_(request_frames_ + kKernelSize), 159 // Create input buffers with a 16-byte alignment for SSE optimizations. 160 kernel_storage_(static_cast<float*>( 161 AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))), 162 kernel_pre_sinc_storage_(static_cast<float*>( 163 AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))), 164 kernel_window_storage_(static_cast<float*>( 165 AlignedMalloc(sizeof(float) * kKernelStorageSize, 16))), 166 input_buffer_(static_cast<float*>( 167 AlignedMalloc(sizeof(float) * input_buffer_size_, 16))), 168 #if defined(WEBRTC_CPU_DETECTION) 169 convolve_proc_(NULL), 170 #endif 171 r1_(input_buffer_.get()), 172 r2_(input_buffer_.get() + kKernelSize / 2) { 173 #if defined(WEBRTC_CPU_DETECTION) 174 InitializeCPUSpecificFeatures(); 175 assert(convolve_proc_); 176 #endif 177 assert(request_frames_ > 0); 178 Flush(); 179 assert(block_size_ > kKernelSize); 180 181 memset(kernel_storage_.get(), 0, 182 sizeof(*kernel_storage_.get()) * kKernelStorageSize); 183 memset(kernel_pre_sinc_storage_.get(), 0, 184 sizeof(*kernel_pre_sinc_storage_.get()) * kKernelStorageSize); 185 memset(kernel_window_storage_.get(), 0, 186 sizeof(*kernel_window_storage_.get()) * kKernelStorageSize); 187 188 InitializeKernel(); 189 } 190 191 SincResampler::~SincResampler() {} 192 193 void SincResampler::UpdateRegions(bool second_load) { 194 // Setup various region pointers in the buffer (see diagram above). If we're 195 // on the second load we need to slide r0_ to the right by kKernelSize / 2. 196 r0_ = input_buffer_.get() + (second_load ? kKernelSize : kKernelSize / 2); 197 r3_ = r0_ + request_frames_ - kKernelSize; 198 r4_ = r0_ + request_frames_ - kKernelSize / 2; 199 block_size_ = r4_ - r2_; 200 201 // r1_ at the beginning of the buffer. 202 assert(r1_ == input_buffer_.get()); 203 // r1_ left of r2_, r4_ left of r3_ and size correct. 204 assert(r2_ - r1_ == r4_ - r3_); 205 // r2_ left of r3. 206 assert(r2_ < r3_); 207 } 208 209 void SincResampler::InitializeKernel() { 210 // Blackman window parameters. 211 static const double kAlpha = 0.16; 212 static const double kA0 = 0.5 * (1.0 - kAlpha); 213 static const double kA1 = 0.5; 214 static const double kA2 = 0.5 * kAlpha; 215 216 // Generates a set of windowed sinc() kernels. 217 // We generate a range of sub-sample offsets from 0.0 to 1.0. 218 const double sinc_scale_factor = SincScaleFactor(io_sample_rate_ratio_); 219 for (int offset_idx = 0; offset_idx <= kKernelOffsetCount; ++offset_idx) { 220 const float subsample_offset = 221 static_cast<float>(offset_idx) / kKernelOffsetCount; 222 223 for (int i = 0; i < kKernelSize; ++i) { 224 const int idx = i + offset_idx * kKernelSize; 225 const float pre_sinc = 226 static_cast<float>(M_PI * (i - kKernelSize / 2 - subsample_offset)); 227 kernel_pre_sinc_storage_[idx] = pre_sinc; 228 229 // Compute Blackman window, matching the offset of the sinc(). 230 const float x = (i - subsample_offset) / kKernelSize; 231 const float window = static_cast<float>(kA0 - kA1 * cos(2.0 * M_PI * x) + 232 kA2 * cos(4.0 * M_PI * x)); 233 kernel_window_storage_[idx] = window; 234 235 // Compute the sinc with offset, then window the sinc() function and store 236 // at the correct offset. 237 kernel_storage_[idx] = static_cast<float>(window * 238 ((pre_sinc == 0) ? 239 sinc_scale_factor : 240 (sin(sinc_scale_factor * pre_sinc) / pre_sinc))); 241 } 242 } 243 } 244 245 void SincResampler::SetRatio(double io_sample_rate_ratio) { 246 if (fabs(io_sample_rate_ratio_ - io_sample_rate_ratio) < 247 std::numeric_limits<double>::epsilon()) { 248 return; 249 } 250 251 io_sample_rate_ratio_ = io_sample_rate_ratio; 252 253 // Optimize reinitialization by reusing values which are independent of 254 // |sinc_scale_factor|. Provides a 3x speedup. 255 const double sinc_scale_factor = SincScaleFactor(io_sample_rate_ratio_); 256 for (int offset_idx = 0; offset_idx <= kKernelOffsetCount; ++offset_idx) { 257 for (int i = 0; i < kKernelSize; ++i) { 258 const int idx = i + offset_idx * kKernelSize; 259 const float window = kernel_window_storage_[idx]; 260 const float pre_sinc = kernel_pre_sinc_storage_[idx]; 261 262 kernel_storage_[idx] = static_cast<float>(window * 263 ((pre_sinc == 0) ? 264 sinc_scale_factor : 265 (sin(sinc_scale_factor * pre_sinc) / pre_sinc))); 266 } 267 } 268 } 269 270 void SincResampler::Resample(int frames, float* destination) { 271 int remaining_frames = frames; 272 273 // Step (1) -- Prime the input buffer at the start of the input stream. 274 if (!buffer_primed_ && remaining_frames) { 275 read_cb_->Run(request_frames_, r0_); 276 buffer_primed_ = true; 277 } 278 279 // Step (2) -- Resample! const what we can outside of the loop for speed. It 280 // actually has an impact on ARM performance. See inner loop comment below. 281 const double current_io_ratio = io_sample_rate_ratio_; 282 const float* const kernel_ptr = kernel_storage_.get(); 283 while (remaining_frames) { 284 // |i| may be negative if the last Resample() call ended on an iteration 285 // that put |virtual_source_idx_| over the limit. 286 // 287 // Note: The loop construct here can severely impact performance on ARM 288 // or when built with clang. See https://codereview.chromium.org/18566009/ 289 for (int i = static_cast<int>( 290 ceil((block_size_ - virtual_source_idx_) / current_io_ratio)); 291 i > 0; --i) { 292 assert(virtual_source_idx_ < block_size_); 293 294 // |virtual_source_idx_| lies in between two kernel offsets so figure out 295 // what they are. 296 const int source_idx = static_cast<int>(virtual_source_idx_); 297 const double subsample_remainder = virtual_source_idx_ - source_idx; 298 299 const double virtual_offset_idx = 300 subsample_remainder * kKernelOffsetCount; 301 const int offset_idx = static_cast<int>(virtual_offset_idx); 302 303 // We'll compute "convolutions" for the two kernels which straddle 304 // |virtual_source_idx_|. 305 const float* const k1 = kernel_ptr + offset_idx * kKernelSize; 306 const float* const k2 = k1 + kKernelSize; 307 308 // Ensure |k1|, |k2| are 16-byte aligned for SIMD usage. Should always be 309 // true so long as kKernelSize is a multiple of 16. 310 assert(0u == (reinterpret_cast<uintptr_t>(k1) & 0x0F)); 311 assert(0u == (reinterpret_cast<uintptr_t>(k2) & 0x0F)); 312 313 // Initialize input pointer based on quantized |virtual_source_idx_|. 314 const float* const input_ptr = r1_ + source_idx; 315 316 // Figure out how much to weight each kernel's "convolution". 317 const double kernel_interpolation_factor = 318 virtual_offset_idx - offset_idx; 319 *destination++ = CONVOLVE_FUNC( 320 input_ptr, k1, k2, kernel_interpolation_factor); 321 322 // Advance the virtual index. 323 virtual_source_idx_ += current_io_ratio; 324 325 if (!--remaining_frames) 326 return; 327 } 328 329 // Wrap back around to the start. 330 virtual_source_idx_ -= block_size_; 331 332 // Step (3) -- Copy r3_, r4_ to r1_, r2_. 333 // This wraps the last input frames back to the start of the buffer. 334 memcpy(r1_, r3_, sizeof(*input_buffer_.get()) * kKernelSize); 335 336 // Step (4) -- Reinitialize regions if necessary. 337 if (r0_ == r2_) 338 UpdateRegions(true); 339 340 // Step (5) -- Refresh the buffer with more input. 341 read_cb_->Run(request_frames_, r0_); 342 } 343 } 344 345 #undef CONVOLVE_FUNC 346 347 int SincResampler::ChunkSize() const { 348 return static_cast<int>(block_size_ / io_sample_rate_ratio_); 349 } 350 351 void SincResampler::Flush() { 352 virtual_source_idx_ = 0; 353 buffer_primed_ = false; 354 memset(input_buffer_.get(), 0, 355 sizeof(*input_buffer_.get()) * input_buffer_size_); 356 UpdateRegions(false); 357 } 358 359 float SincResampler::Convolve_C(const float* input_ptr, const float* k1, 360 const float* k2, 361 double kernel_interpolation_factor) { 362 float sum1 = 0; 363 float sum2 = 0; 364 365 // Generate a single output sample. Unrolling this loop hurt performance in 366 // local testing. 367 int n = kKernelSize; 368 while (n--) { 369 sum1 += *input_ptr * *k1++; 370 sum2 += *input_ptr++ * *k2++; 371 } 372 373 // Linearly interpolate the two "convolutions". 374 return static_cast<float>((1.0 - kernel_interpolation_factor) * sum1 + 375 kernel_interpolation_factor * sum2); 376 } 377 378 } // namespace webrtc 379
