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