74 lines
3.5 KiB
C++
74 lines
3.5 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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#ifndef RESAMPLER_H
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#define RESAMPLER_H
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#include <cstddef>
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/** Interface to a Resampler. */
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class Resampler {
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long inRate_;
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long outRate_;
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protected:
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void setRate(const long inRate, const long outRate) { inRate_ = inRate; outRate_ = outRate; }
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Resampler() : inRate_(0), outRate_(0) {}
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public:
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/** Returns the sampling rate of the input that this resampler expects. */
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long inRate() const { return inRate_; }
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/** Returns the approximate sampling rate of the output. */
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long outRate() const { return outRate_; }
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/** Can be used to adjust the input and output sampling rates slightly with minimal disturbance in the output.
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* Should only be used for slight changes or the quality could detoriate.
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* It can for instance be useful to tweak the output rate slightly to synchronize production speed to playback
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* speed when synchronizing video frame rate to refresh rate while playing back audio from the same source.
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* This can reduce skipped or duplicated video frames (or avoid audio underruns if no frame skipping is done).
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*
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* @param inRate New input sampling rate.
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* @param outRate Desired new output sampling rate.
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*/
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virtual void adjustRate(long inRate, long outRate) = 0;
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/** Returns the exact ratio that this resampler is configured to use,
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* such that the actual output sampling rate is (input rate) * mul / div.
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* outRate() / inRate() is not necessarily equal to mul / div.
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* Many resampler are intended for real-time purposes where it does not matter
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* much whether the output sampling rate is 100% exact. Playback hardware is also slightly off.
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*/
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virtual void exactRatio(unsigned long &mul, unsigned long &div) const = 0;
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/** Returns an upper bound on how many samples are produced for 'inlen' input samples.
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* Can be used to calculate buffer sizes.
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*/
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virtual std::size_t maxOut(std::size_t inlen) const = 0;
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/** Resamples the samples in 'in' and puts the resulting samples in 'out'.
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*
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* @param inlen The number of samples in 'in' to be resampled/consumed.
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* @return The number of samples produced in 'out'.
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*/
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virtual std::size_t resample(short *out, const short *in, std::size_t inlen) = 0;
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virtual ~Resampler() {}
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};
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#endif
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