89 lines
3.2 KiB
C++
89 lines
3.2 KiB
C++
/***************************************************************************
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* Copyright (C) 2008 by Sindre Aamås *
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* sinamas@users.sourceforge.net *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License version 2 as *
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* published by the Free Software Foundation. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License version 2 for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* version 2 along with this program; if not, write to the *
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* Free Software Foundation, Inc., *
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
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***************************************************************************/
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#include "rateest.h"
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#include <cstdlib>
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void RateEst::SumQueue::push(std::ptrdiff_t const samples, usec_t const usecs) {
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q_.push_back(std::make_pair(samples, usecs));
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samples_ += samples;
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usecs_ += usecs;
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}
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void RateEst::SumQueue::pop() {
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std::pair<std::ptrdiff_t, usec_t> const &f = q_.front();
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samples_ -= f.first;
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usecs_ -= f.second;
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q_.pop_front();
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}
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static usec_t sampleUsecs(std::ptrdiff_t samples, long rate) {
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return usec_t((samples * 1000000.0f) / (rate ? rate : 1) + 0.5f);
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}
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static long limit(long est, long const reference) {
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if (est > reference + (reference >> 6))
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est = reference + (reference >> 6);
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else if (est < reference - (reference >> 6))
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est = reference - (reference >> 6);
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return est;
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}
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enum { mean_scale = 1 << 5 };
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RateEst::RateEst(long const nominalSampleRate, std::size_t const maxValidFeedPeriodSamples)
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: srate_(nominalSampleRate * est_scale)
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, reference_(srate_)
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, maxPeriod_(sampleUsecs(maxValidFeedPeriodSamples, nominalSampleRate))
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, last_(0)
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, usecs_(12000000 * mean_scale)
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, samples_(nominalSampleRate * 12 * mean_scale)
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{
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}
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void RateEst::feed(std::ptrdiff_t samplesIn, usec_t const now) {
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usec_t usecsIn = now - last_;
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if (last_ && usecsIn < maxPeriod_) {
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sumq_.push(samplesIn, usecsIn);
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while ((usecsIn = sumq_.usecs()) > 100000) {
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samplesIn = sumq_.samples();
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sumq_.pop();
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long const srateIn = long(samplesIn * (1000000.0f * est_scale) / usecsIn);
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if (std::abs(srateIn - reference_) < reference_ >> 1) {
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samples_ += (samplesIn - sumq_.samples()) * mean_scale;
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usecs_ += ( usecsIn - sumq_.usecs() ) * mean_scale;
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long est = long(samples_ * (1000000.0f * est_scale) / usecs_ + 0.5f);
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est = limit((srate_ * 31 + est + 16) >> 5, reference_);
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srate_ = est;
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if (usecs_ > 16000000 * mean_scale) {
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samples_ = (samples_ * 3 + 2) >> 2;
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usecs_ = (usecs_ * 3 + 2) >> 2;
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}
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}
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}
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}
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last_ = now;
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}
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