75 lines
1.9 KiB
C++
75 lines
1.9 KiB
C++
// Copyright 2014 Google Inc. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#include "packager/mpd/base/bandwidth_estimator.h"
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#include <cmath>
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#include "packager/base/logging.h"
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namespace shaka {
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BandwidthEstimator::BandwidthEstimator(size_t num_blocks)
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: sliding_queue_(num_blocks) {}
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BandwidthEstimator::~BandwidthEstimator() {}
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void BandwidthEstimator::AddBlock(uint64_t size, double duration) {
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DCHECK_GT(duration, 0.0);
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DCHECK_GT(size, 0u);
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const int kBitsInByte = 8;
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const double bits_per_second_reciprocal = duration / (kBitsInByte * size);
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sliding_queue_.Add(bits_per_second_reciprocal);
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}
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uint64_t BandwidthEstimator::Estimate() const {
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return sliding_queue_.size() == 0
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? 0
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: static_cast<uint64_t>(
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ceil(sliding_queue_.size() / sliding_queue_.sum()));
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}
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uint64_t BandwidthEstimator::Max() const {
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// The first element has minimum "bits per second reciprocal", thus the
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// reverse is maximum "bits per second".
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return sliding_queue_.size() == 0
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? 0
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: static_cast<uint64_t>(ceil(1 / sliding_queue_.min()));
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}
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BandwidthEstimator::SlidingQueue::SlidingQueue(size_t window_size)
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: window_size_(window_size) {}
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void BandwidthEstimator::SlidingQueue::Add(double value) {
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// Remove elements if needed to form a monotonic non-decreasing sequence.
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while (!min_.empty() && min_.back() > value)
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min_.pop_back();
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min_.push_back(value);
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if (window_size_ == kUseAllBlocks) {
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size_++;
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sum_ += value;
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min_.resize(1); // Keep only the minimum one.
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return;
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}
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window_.push_back(value);
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sum_ += value;
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if (window_.size() <= window_size_) {
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size_++;
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return;
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}
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if (min_.front() == window_.front())
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min_.pop_front();
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sum_ -= window_.front();
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window_.pop_front();
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}
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} // namespace shaka
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