| /* |
| * Copyright 2024 The WebRTC project authors. All rights reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #include "video/corruption_detection/halton_sequence.h" |
| |
| #include <algorithm> |
| #include <vector> |
| |
| #include "rtc_base/checks.h" |
| |
| namespace webrtc { |
| namespace { |
| |
| static constexpr int kMaxDimensions = 5; |
| const int kBases[kMaxDimensions] = {2, 3, 5, 7, 11}; |
| |
| double GetVanDerCorputSequenceElement(int sequence_idx, int base) { |
| if (sequence_idx < 0 || base < 2) { |
| sequence_idx = 0; |
| base = 2; |
| } |
| double element = 0.0; |
| double positional_value = 1.0; |
| int left = sequence_idx; |
| while (left > 0) { |
| positional_value /= base; |
| element += positional_value * (left % base); |
| left /= base; |
| } |
| return element; |
| } |
| |
| } // namespace |
| |
| HaltonSequence::HaltonSequence(int num_dimensions) |
| : num_dimensions_(num_dimensions), current_idx_(0) { |
| RTC_CHECK_GE(num_dimensions_, 1) |
| << "num_dimensions must be >= 1. Will be set to 1."; |
| RTC_CHECK_LE(num_dimensions_, kMaxDimensions) |
| << "num_dimensions must be <= " << kMaxDimensions << ". Will be set to " |
| << kMaxDimensions << "."; |
| num_dimensions_ = std::clamp(num_dimensions_, 1, kMaxDimensions); |
| } |
| |
| std::vector<double> HaltonSequence::GetNext() { |
| std::vector<double> point = {}; |
| point.reserve(num_dimensions_); |
| for (int i = 0; i < num_dimensions_; ++i) { |
| point.push_back(GetVanDerCorputSequenceElement(current_idx_, kBases[i])); |
| } |
| ++current_idx_; |
| return point; |
| } |
| |
| void HaltonSequence::Reset() { |
| HaltonSequence::current_idx_ = 0; |
| } |
| |
| } // namespace webrtc |