| /* |
| * Copyright (c) 2012 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 "webrtc/modules/audio_coding/neteq/buffer_level_filter.h" |
| |
| #include <algorithm> // Provide access to std::max. |
| |
| namespace webrtc { |
| |
| BufferLevelFilter::BufferLevelFilter() { |
| Reset(); |
| } |
| |
| void BufferLevelFilter::Reset() { |
| filtered_current_level_ = 0; |
| level_factor_ = 253; |
| } |
| |
| void BufferLevelFilter::Update(size_t buffer_size_packets, |
| int time_stretched_samples, |
| size_t packet_len_samples) { |
| // Filter: |
| // |filtered_current_level_| = |level_factor_| * |filtered_current_level_| + |
| // (1 - |level_factor_|) * |buffer_size_packets| |
| // |level_factor_| and |filtered_current_level_| are in Q8. |
| // |buffer_size_packets| is in Q0. |
| filtered_current_level_ = ((level_factor_ * filtered_current_level_) >> 8) + |
| ((256 - level_factor_) * static_cast<int>(buffer_size_packets)); |
| |
| // Account for time-scale operations (accelerate and pre-emptive expand). |
| if (time_stretched_samples && packet_len_samples > 0) { |
| // Time-scaling has been performed since last filter update. Subtract the |
| // value of |time_stretched_samples| from |filtered_current_level_| after |
| // converting |time_stretched_samples| from samples to packets in Q8. |
| // Make sure that the filtered value remains non-negative. |
| filtered_current_level_ = std::max(0, |
| filtered_current_level_ - |
| (time_stretched_samples << 8) / static_cast<int>(packet_len_samples)); |
| } |
| } |
| |
| void BufferLevelFilter::SetTargetBufferLevel(int target_buffer_level) { |
| if (target_buffer_level <= 1) { |
| level_factor_ = 251; |
| } else if (target_buffer_level <= 3) { |
| level_factor_ = 252; |
| } else if (target_buffer_level <= 7) { |
| level_factor_ = 253; |
| } else { |
| level_factor_ = 254; |
| } |
| } |
| |
| int BufferLevelFilter::filtered_current_level() const { |
| return filtered_current_level_; |
| } |
| |
| } // namespace webrtc |