kopia lustrzana https://github.com/markondej/fm_transmitter
73 wiersze
2.6 KiB
C++
73 wiersze
2.6 KiB
C++
/*
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fm_transmitter - use Raspberry Pi as FM transmitter
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Copyright (c) 2019, Marcin Kondej
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All rights reserved.
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See https://github.com/markondej/fm_transmitter
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Redistribution and use in source and binary forms, with or without modification, are
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permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this list
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of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice, this
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list of conditions and the following disclaimer in the documentation and/or other
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materials provided with the distribution.
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3. Neither the name of the copyright holder nor the names of its contributors may be
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used to endorse or promote products derived from this software without specific
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prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
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WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "sample.hpp"
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#include <climits>
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Sample::Sample(uint8_t *data, uint16_t channels, uint16_t bitsPerChannel)
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: value(0.)
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{
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int32_t sum = 0;
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int16_t *channelValues = new int16_t[channels];
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int16_t multiplier = bitsPerChannel >> 3;
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for (uint32_t i = 0; i < channels; i++) {
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if (multiplier > 1) {
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channelValues[i] = (data[(i + 1) * multiplier - 1] << 8) | data[(i + 1) * multiplier - 2];
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} else {
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channelValues[i] = (static_cast<int16_t>(data[i]) - 0x80) << 8;
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}
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sum += channelValues[i];
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}
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value = 2 * sum / channels / static_cast<double>(USHRT_MAX);
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delete[] channelValues;
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}
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double Sample::getMonoValue()
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{
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return value;
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}
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#ifndef NO_PREEMP
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PreEmphasis::PreEmphasis(uint32_t sampleRate)
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: timeConst(sampleRate * 75.0e-6), prevValue(0.)
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{
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}
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double PreEmphasis::filter(double value)
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{
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prevValue = value;
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value = value + (prevValue - value) / (1. - timeConst);
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return value;
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}
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#endif
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