73 lines
2.5 KiB
C++
73 lines
2.5 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 <algorithm>
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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(double target_segment_duration)
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: target_segment_duration_(target_segment_duration) {}
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BandwidthEstimator::~BandwidthEstimator() = default;
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void BandwidthEstimator::AddBlock(uint64_t size_in_bytes, double duration) {
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if (size_in_bytes == 0 || duration == 0) {
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LOG(WARNING) << "Ignore block with size=" << size_in_bytes
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<< ", duration=" << duration;
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return;
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}
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const int kBitsInByte = 8;
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const uint64_t size_in_bits = size_in_bytes * kBitsInByte;
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total_size_in_bits_ += size_in_bits;
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total_duration_ += duration;
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const uint64_t bitrate = static_cast<uint64_t>(ceil(size_in_bits / duration));
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if (duration < 0.5 * target_segment_duration_) {
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// https://tools.ietf.org/html/rfc8216#section-4.1
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// The peak segment bit rate of a Media Playlist is the largest bit rate of
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// any continuous set of segments whose total duration is between 0.5
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// and 1.5 times the target duration.
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// Only the short segments are excluded here as our media playlist generator
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// sets the target duration in the playlist to the largest segment duration.
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// So although the segment duration could be 1.5 times the user provided
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// segment duration, it will never be larger than the actual target
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// duration.
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//
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// TODO(kqyang): Review if we can just stick to the user provided segment
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// duration as our target duration.
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//
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// We also apply the same exclusion to the bandwidth computation for DASH as
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// the bitrate for the short segment is not a good signal for peak
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// bandwidth.
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// See https://github.com/google/shaka-packager/issues/498 for details.
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VLOG(1) << "Exclude short segment (duration " << duration
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<< ", target_duration " << target_segment_duration_
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<< ") in peak bandwidth computation.";
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return;
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}
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max_bitrate_ = std::max(bitrate, max_bitrate_);
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}
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uint64_t BandwidthEstimator::Estimate() const {
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if (total_duration_ == 0)
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return 0;
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return static_cast<uint64_t>(ceil(total_size_in_bits_ / total_duration_));
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}
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uint64_t BandwidthEstimator::Max() const {
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return max_bitrate_;
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}
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} // namespace shaka
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