jcs.org
fork of PCE focusing on macplus, supporting DaynaPort SCSI network emulation
sound: Add a volume adjustment filter function
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src/drivers/sound/filter.c
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src/drivers/sound/filter.c
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/*****************************************************************************
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* File name: src/drivers/sound/filter.c *
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* Created: 2010-08-27 by Hampa Hug <hampa@hampa.ch> *
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* Copyright: (C) 2010 Hampa Hug <hampa@hampa.ch> *
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* Copyright: (C) 2010-2025 Hampa Hug <hampa@hampa.ch> *
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*****************************************************************************/
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/*****************************************************************************
···
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* *
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* This program is distributed in the hope that it will be useful, but *
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* WITHOUT ANY WARRANTY, without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General *
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* Public License for more details. *
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*****************************************************************************/
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···
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#define SND_IIR_MUL 8192
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void snd_volume (uint16_t *dst, const uint16_t *src, unsigned long cnt, unsigned volume, int sign)
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{
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unsigned long i;
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long val, vol;
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unsigned sig;
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sig = sign ? 0x8000 : 0x0000;
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vol = (long) volume;
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for (i = 0; i < cnt; i++) {
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val = (long) (src[i] ^ sig) - 32768;
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val = (vol * val + 127) / 256 + 32768;
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if (val < 0) {
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val = 0;
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}
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else if (val > 65535) {
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val = 65535;
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}
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dst[i] = (unsigned) val ^ sig;
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}
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}
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void snd_iir2_init (sound_iir2_t *iir)
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{
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src/drivers/sound/filter.h
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src/drivers/sound/filter.h
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/*****************************************************************************
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* File name: src/drivers/sound/sound.h *
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* Created: 2010-08-27 by Hampa Hug <hampa@hampa.ch> *
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* Copyright: (C) 2010 Hampa Hug <hampa@hampa.ch> *
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* Copyright: (C) 2010-2025 Hampa Hug <hampa@hampa.ch> *
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*****************************************************************************/
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/*****************************************************************************
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* *
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* This program is distributed in the hope that it will be useful, but *
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* WITHOUT ANY WARRANTY, without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General *
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* Public License for more details. *
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*****************************************************************************/
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···
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long y[3];
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} sound_iir2_t;
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/*!***************************************************************************
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* @short Adjust the volume
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* @param dst The destination buffer
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* @param src The source buffer
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* @param cnt The sample count
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* @param volume The volume adjustment is (volume / 256)
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* @param sign The sample signedness in both src and dst
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*****************************************************************************/
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void snd_volume (uint16_t *dst, const uint16_t *src, unsigned long cnt, unsigned volume, int sign);
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/*!***************************************************************************
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* @short Initialize an IIR2 filter