118 lines
3.0 KiB
C++
118 lines
3.0 KiB
C++
/*
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* Copyright (C) 2003-2014 The Music Player Daemon Project
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* http://www.musicpd.org
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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 as published by
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* the Free Software Foundation; either version 2 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 General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#include "PcmDither.hxx"
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#include "PcmPrng.hxx"
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#include "Traits.hxx"
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template<typename T, T MIN, T MAX, unsigned scale_bits>
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inline T
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PcmDither::Dither(T sample)
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{
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constexpr T round = 1 << (scale_bits - 1);
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constexpr T mask = (1 << scale_bits) - 1;
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sample += error[0] - error[1] + error[2];
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error[2] = error[1];
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error[1] = error[0] / 2;
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/* round */
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T output = sample + round;
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const T rnd = pcm_prng(random);
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output += (rnd & mask) - (random & mask);
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random = rnd;
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/* clip */
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if (output > MAX) {
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output = MAX;
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if (sample > MAX)
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sample = MAX;
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} else if (output < MIN) {
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output = MIN;
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if (sample < MIN)
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sample = MIN;
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}
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output &= ~mask;
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error[0] = sample - output;
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return output >> scale_bits;
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}
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template<typename ST, unsigned SBITS, unsigned DBITS>
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inline ST
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PcmDither::DitherShift(ST sample)
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{
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static_assert(sizeof(ST) * 8 > SBITS, "Source type too small");
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static_assert(SBITS > DBITS, "Non-positive scale_bits");
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static constexpr ST MIN = -(ST(1) << (SBITS - 1));
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static constexpr ST MAX = (ST(1) << (SBITS - 1)) - 1;
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return Dither<ST, MIN, MAX, SBITS - DBITS>(sample);
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}
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template<typename ST, typename DT>
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inline typename DT::value_type
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PcmDither::DitherConvert(typename ST::value_type sample)
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{
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static_assert(ST::BITS > DT::BITS,
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"Sample formats cannot be dithered");
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constexpr unsigned scale_bits = ST::BITS - DT::BITS;
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return Dither<typename ST::sum_type, ST::MIN, ST::MAX,
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scale_bits>(sample);
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}
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template<typename ST, typename DT>
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inline void
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PcmDither::DitherConvert(typename DT::pointer_type dest,
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typename ST::const_pointer_type src,
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typename ST::const_pointer_type src_end)
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{
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while (src < src_end)
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*dest++ = DitherConvert<ST, DT>(*src++);
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}
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inline void
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PcmDither::Dither24To16(int16_t *dest, const int32_t *src,
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const int32_t *src_end)
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{
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typedef SampleTraits<SampleFormat::S24_P32> ST;
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typedef SampleTraits<SampleFormat::S16> DT;
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DitherConvert<ST, DT>(dest, src, src_end);
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}
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inline void
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PcmDither::Dither32To16(int16_t *dest, const int32_t *src,
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const int32_t *src_end)
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{
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typedef SampleTraits<SampleFormat::S32> ST;
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typedef SampleTraits<SampleFormat::S16> DT;
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DitherConvert<ST, DT>(dest, src, src_end);
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}
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