dbc223eb84
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71 lines
2.2 KiB
C
71 lines
2.2 KiB
C
/*(LGPL)
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---------------------------------------------------------------------------
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a_limiter.h - Simple limiter
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---------------------------------------------------------------------------
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* Copyright (C) 2001. 2002, David Olofson
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or (at
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* 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, 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
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _A_LIMITER_H_
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#define _A_LIMITER_H_
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typedef struct limiter_t
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{
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int samplerate;
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unsigned threshold; /* Reaction threshold */
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int release; /* Release "speed" */
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unsigned peak; /* Filtered peak value */
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unsigned attenuation; /* Current output attenuation */
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} limiter_t;
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enum lim_params_t
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{
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LIM_THRESHOLD = 0, /* 16 bit sample units */
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LIM_RELEASE /* Units per second */
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};
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int lim_open(limiter_t *lim, int samplerate);
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void lim_close(limiter_t *lim);
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void lim_control(limiter_t *lim, int param, int value);
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/*
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* Limiter stereo process function.
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* Supports in-place processing.
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*/
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void lims_process(limiter_t *lim, int *in, int *out, unsigned frames);
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/*
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* Smart Stereo version.
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*
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* This algorithm takes both channels in account in a way
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* that reduces the effect of the center appearing to have
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* more power after compression of signals with unbalanced
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* stereo images.
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*
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* A dead center signal can only get 3 dB louder than the
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* same signal in one channel only, as opposed to the
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* normal 6 dB of a limiter that only looks at max(L, R).
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*
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* Meanwhile, with "normal" material (ie most power
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* relatively centered), this limiter gets an extra 3 dB
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* compared to a limiter that checks (L+R).
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*/
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void limss_process(limiter_t *lim, int *in, int *out, unsigned frames);
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#endif /*_A_LIMITER_H_*/
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