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64 lines
2.6 KiB
C++
64 lines
2.6 KiB
C++
/* Copyright (C) 2015-2022 Sergey V. Mikayev
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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 Lesser General Public License as published by
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* the Free Software Foundation, either version 2.1 of the License, or
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* (at your option) any later version.
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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 Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef SRCTOOLS_RESAMPLER_MODEL_H
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#define SRCTOOLS_RESAMPLER_MODEL_H
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#include "FloatSampleProvider.h"
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namespace SRCTools {
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class ResamplerStage;
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/** Model consists of one or more ResampleStage instances connected in a cascade. */
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namespace ResamplerModel {
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// Seems to be a good choice for 16-bit integer samples.
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static const double DEFAULT_DB_SNR = 106;
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// When using linear interpolation, oversampling factor necessary to achieve the DEFAULT_DB_SNR is about 256.
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// This figure is the upper estimation, and it can be found by analysing the frequency response of the linear interpolator.
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// When less SNR is desired, this value should also decrease in accordance.
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static const unsigned int DEFAULT_WINDOWED_SINC_MAX_DOWNSAMPLE_FACTOR = 256;
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// In the default resampler model, the input to the windowed sinc filter is always at least 2x oversampled during upsampling,
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// so oversampling factor of 128 should be sufficient to achieve the DEFAULT_DB_SNR with linear interpolation.
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static const unsigned int DEFAULT_WINDOWED_SINC_MAX_UPSAMPLE_FACTOR = DEFAULT_WINDOWED_SINC_MAX_DOWNSAMPLE_FACTOR / 2;
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enum Quality {
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// Use when the speed is more important than the audio quality.
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FASTEST,
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// Use FAST quality setting of the IIR stage (50% of passband retained).
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FAST,
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// Use GOOD quality setting of the IIR stage (77% of passband retained).
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GOOD,
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// Use BEST quality setting of the IIR stage (95% of passband retained).
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BEST
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};
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FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, double sourceSampleRate, double targetSampleRate, Quality quality);
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FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, ResamplerStage **stages, unsigned int stageCount);
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FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, ResamplerStage &stage);
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void freeResamplerModel(FloatSampleProvider &model, FloatSampleProvider &source);
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} // namespace ResamplerModel
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} // namespace SRCTools
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#endif // SRCTOOLS_RESAMPLER_MODEL_H
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