dbc223eb84
Import existing source tree; original VCS history is no longer available. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
141 lines
3.4 KiB
C
141 lines
3.4 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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#include <stdlib.h>
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#include "a_limiter.h"
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#include "a_types.h"
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int lim_open(limiter_t *lim, int samplerate)
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{
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lim->samplerate = samplerate;
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lim_control(lim, LIM_THRESHOLD, 32768);
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lim_control(lim, LIM_RELEASE, 300000);
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lim->peak = (unsigned)(32768<<8);
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lim->attenuation = 0;
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return 0;
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}
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void lim_close(limiter_t *lim)
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{
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/* Nothing to destruct */
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}
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void lim_control(limiter_t *lim, int param, int value)
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{
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switch(param)
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{
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case LIM_THRESHOLD:
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lim->threshold = (unsigned)(value << 8);
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if(lim->threshold < 256)
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lim->threshold = 256;
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break;
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case LIM_RELEASE:
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if(lim->samplerate < 1)
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lim->samplerate = 44100;
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lim->release = (value << 8) / lim->samplerate;
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break;
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}
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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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unsigned i;
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frames <<= 1;
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for(i = 0; i < frames; i += 2)
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{
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int gain;
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int lp = abs(in[i]) << 8;
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int rp = abs(in[i+1]) << 8;
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unsigned maxp = (unsigned)(lp > rp ? lp : rp);
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if(maxp > lim->peak)
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{
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lim->peak = maxp;
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gain = (32767<<16) / ((lim->peak+255)>>8);
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}
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else
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{
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gain = (32767<<16) / ((lim->peak+255)>>8);
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lim->peak -= lim->release;
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if(lim->peak < lim->threshold)
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lim->peak = lim->threshold;
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}
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#ifdef A_USE_INT64
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out[i] = (Sint64)in[i] * (Sint64)gain >> 16;
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out[i+1] = (Sint64)in[i+1] * (Sint64)gain >> 16;
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#else
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if(gain < 8192)
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{
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out[i] = in[i] * gain >> 16;
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out[i+1] = in[i+1] * gain >> 16;
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}
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else
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{
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out[i] = in[i] * (gain>>4) >> 12;
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out[i+1] = in[i+1] * (gain>>4) >> 12;
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}
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#endif
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}
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lim->attenuation = (lim->peak - lim->threshold) >> 8;
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}
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void limss_process(limiter_t *lim, int *in, int *out, unsigned frames)
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{
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unsigned i;
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frames <<= 1;
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for(i = 0; i < frames; i += 2)
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{
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int gain;
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int lp = abs(in[i]);
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int rp = abs(in[i+1]);
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unsigned maxp = (unsigned)(lp > rp ? lp : rp);
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unsigned p = maxp << 8;
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p += (maxp - abs(lp - rp)) << 7;
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if(p > lim->peak)
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{
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lim->peak = p;
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gain = (32767<<16) / ((lim->peak+255)>>8);
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}
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else
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{
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gain = (32767<<16) / ((lim->peak+255)>>8);
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lim->peak -= lim->release;
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if(lim->peak < lim->threshold)
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lim->peak = lim->threshold;
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}
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#ifdef A_USE_INT64
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out[i] = (Sint64)in[i] * (Sint64)gain >> 16;
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out[i+1] = (Sint64)in[i+1] * (Sint64)gain >> 16;
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#else
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if(gain < 8192)
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{
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out[i] = in[i] * gain >> 16;
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out[i+1] = in[i+1] * gain >> 16;
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}
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else
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{
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out[i] = in[i] * (gain>>4) >> 12;
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out[i+1] = in[i+1] * (gain>>4) >> 12;
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}
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#endif
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}
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lim->attenuation = (lim->peak - lim->threshold) >> 8;
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}
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