1 /* 2 * Copyright 2003-2021 The Music Player Daemon Project 3 * http://www.musicpd.org 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License along 16 * with this program; if not, write to the Free Software Foundation, Inc., 17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 18 */ 19 20 #ifndef MPD_PCM_DITHER_HXX 21 #define MPD_PCM_DITHER_HXX 22 23 #include <cstdint> 24 25 enum class SampleFormat : uint8_t; 26 27 class PcmDither { 28 int32_t error[3]; 29 int32_t random; 30 31 public: PcmDither()32 constexpr PcmDither() noexcept 33 :error{0, 0, 0}, random(0) {} 34 35 /** 36 * Shift the given sample by #SBITS-#DBITS to the right, and 37 * apply dithering. 38 * 39 * @tparam ST the input sample type 40 * @tparam SBITS the input bit width 41 * @tparam DBITS the output bit width 42 * @param sample the input sample value 43 */ 44 template<typename ST, unsigned SBITS, unsigned DBITS> 45 ST DitherShift(ST sample) noexcept; 46 47 void Dither24To16(int16_t *dest, const int32_t *src, 48 const int32_t *src_end) noexcept; 49 50 void Dither32To16(int16_t *dest, const int32_t *src, 51 const int32_t *src_end) noexcept; 52 53 private: 54 /** 55 * Shift the given sample by #scale_bits to the right, and 56 * apply dithering. 57 * 58 * @param T the input sample type 59 * @param MIN the minimum input sample value 60 * @param MAX the maximum input sample value 61 * @param scale_bits the number of bits to be discarded 62 * @param sample the input sample value 63 */ 64 template<typename T, T MIN, T MAX, unsigned scale_bits> 65 T Dither(T sample) noexcept; 66 67 /** 68 * Convert the given sample from one sample format to another, 69 * discarding bits. 70 * 71 * @param ST the input #SampleTraits class 72 * @param ST the output #SampleTraits class 73 * @param sample the input sample value 74 */ 75 template<typename ST, typename DT> 76 typename DT::value_type DitherConvert(typename ST::value_type sample) noexcept; 77 78 template<typename ST, typename DT> 79 void DitherConvert(typename DT::pointer dest, 80 typename ST::const_pointer src, 81 typename ST::const_pointer src_end) noexcept; 82 }; 83 84 #endif 85