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/*
* Copyright (c) 2021 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 "modules/audio_coding/neteq/reorder_optimizer.h"
#include <algorithm>
#include <limits>
#include <vector>
namespace webrtc {
namespace {
constexpr int kDelayBuckets = 100;
constexpr int kBucketSizeMs = 20;
} // namespace
ReorderOptimizer::ReorderOptimizer(int forget_factor,
int ms_per_loss_percent,
absl::optional<int> start_forget_weight)
: histogram_(kDelayBuckets, forget_factor, start_forget_weight),
ms_per_loss_percent_(ms_per_loss_percent) {}
void ReorderOptimizer::Update(int relative_delay_ms,
bool reordered,
int base_delay_ms) {
const int index = reordered ? relative_delay_ms / kBucketSizeMs : 0;
if (index < histogram_.NumBuckets()) {
// Maximum delay to register is 2000 ms.
histogram_.Add(index);
}
int bucket_index = MinimizeCostFunction(base_delay_ms);
optimal_delay_ms_ = (1 + bucket_index) * kBucketSizeMs;
}
void ReorderOptimizer::Reset() {
histogram_.Reset();
optimal_delay_ms_.reset();
}
int ReorderOptimizer::MinimizeCostFunction(int base_delay_ms) const {
const std::vector<int>& buckets = histogram_.buckets();
// Values are calculated in Q30.
int64_t loss_probability = 1 << 30;
int64_t min_cost = std::numeric_limits<int64_t>::max();
int min_bucket = 0;
for (int i = 0; i < static_cast<int>(buckets.size()); ++i) {
loss_probability -= buckets[i];
int64_t delay_ms =
static_cast<int64_t>(std::max(0, i * kBucketSizeMs - base_delay_ms))
<< 30;
int64_t cost = delay_ms + 100 * ms_per_loss_percent_ * loss_probability;
if (cost < min_cost) {
min_cost = cost;
min_bucket = i;
}
if (loss_probability == 0) {
break;
}
}
return min_bucket;
}
} // namespace webrtc