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/* Copyright (C) 2015-2017 Sergey V. Mikayev
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef SRCTOOLS_RESAMPLER_MODEL_H
#define SRCTOOLS_RESAMPLER_MODEL_H
#include "FloatSampleProvider.h"
namespace SRCTools {
class ResamplerStage;
/** Model consists of one or more ResampleStage instances connected in a cascade. */
namespace ResamplerModel {
// Seems to be a good choice for 16-bit integer samples.
static const double DEFAULT_DB_SNR = 106;
// When using linear interpolation, oversampling factor necessary to achieve the DEFAULT_DB_SNR is about 256.
// This figure is the upper estimation, and it can be found by analysing the frequency response of the linear interpolator.
// When less SNR is desired, this value should also decrease in accordance.
static const unsigned int DEFAULT_WINDOWED_SINC_MAX_DOWNSAMPLE_FACTOR = 256;
// In the default resampler model, the input to the windowed sinc filter is always at least 2x oversampled during upsampling,
// so oversampling factor of 128 should be sufficient to achieve the DEFAULT_DB_SNR with linear interpolation.
static const unsigned int DEFAULT_WINDOWED_SINC_MAX_UPSAMPLE_FACTOR = DEFAULT_WINDOWED_SINC_MAX_DOWNSAMPLE_FACTOR / 2;
enum Quality {
// Use when the speed is more important than the audio quality.
FASTEST,
// Use FAST quality setting of the IIR stage (50% of passband retained).
FAST,
// Use GOOD quality setting of the IIR stage (77% of passband retained).
GOOD,
// Use BEST quality setting of the IIR stage (95% of passband retained).
BEST
};
FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, double sourceSampleRate, double targetSampleRate, Quality quality);
FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, ResamplerStage **stages, unsigned int stageCount);
FloatSampleProvider &createResamplerModel(FloatSampleProvider &source, ResamplerStage &stage);
void freeResamplerModel(FloatSampleProvider &model, FloatSampleProvider &source);
} // namespace ResamplerModel
} // namespace SRCTools
#endif // SRCTOOLS_RESAMPLER_MODEL_H
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