1 /* 2 * Copyright (c) 2012 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 #include "webrtc/modules/audio_coding/neteq/buffer_level_filter.h" 12 13 #include <algorithm> // Provide access to std::max. 14 15 namespace webrtc { 16 17 BufferLevelFilter::BufferLevelFilter() { 18 Reset(); 19 } 20 21 void BufferLevelFilter::Reset() { 22 filtered_current_level_ = 0; 23 level_factor_ = 253; 24 } 25 26 void BufferLevelFilter::Update(size_t buffer_size_packets, 27 int time_stretched_samples, 28 size_t packet_len_samples) { 29 // Filter: 30 // |filtered_current_level_| = |level_factor_| * |filtered_current_level_| + 31 // (1 - |level_factor_|) * |buffer_size_packets| 32 // |level_factor_| and |filtered_current_level_| are in Q8. 33 // |buffer_size_packets| is in Q0. 34 filtered_current_level_ = ((level_factor_ * filtered_current_level_) >> 8) + 35 ((256 - level_factor_) * static_cast<int>(buffer_size_packets)); 36 37 // Account for time-scale operations (accelerate and pre-emptive expand). 38 if (time_stretched_samples && packet_len_samples > 0) { 39 // Time-scaling has been performed since last filter update. Subtract the 40 // value of |time_stretched_samples| from |filtered_current_level_| after 41 // converting |time_stretched_samples| from samples to packets in Q8. 42 // Make sure that the filtered value remains non-negative. 43 filtered_current_level_ = std::max(0, 44 filtered_current_level_ - 45 (time_stretched_samples << 8) / static_cast<int>(packet_len_samples)); 46 } 47 } 48 49 void BufferLevelFilter::SetTargetBufferLevel(int target_buffer_level) { 50 if (target_buffer_level <= 1) { 51 level_factor_ = 251; 52 } else if (target_buffer_level <= 3) { 53 level_factor_ = 252; 54 } else if (target_buffer_level <= 7) { 55 level_factor_ = 253; 56 } else { 57 level_factor_ = 254; 58 } 59 } 60 61 int BufferLevelFilter::filtered_current_level() const { 62 return filtered_current_level_; 63 } 64 65 } // namespace webrtc 66
