limiter.h

著名的 helix realplayer 基于手机 symbian 系统的 播放器全套源代码

/* ***** BEGIN LICENSE BLOCK ***** 
 * Version: RCSL 1.0/RPSL 1.0 
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 * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved. 
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 * Version 1.0 (the "RPSL") available at 
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 * the file under the RealNetworks Community Source License Version 1.0 
 * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl, 
 * in which case the RCSL will apply. You may also obtain the license terms 
 * directly from RealNetworks.  You may not use this file except in 
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 * This file is part of the Helix DNA Technology. RealNetworks is the 
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/* structure definitions and prototypes for audio limiter */

#ifndef _LIMITER_H_
#define _LIMITER_H_

#ifdef __cplusplus
extern "C" {
#endif

typedef struct LIMSTATE {
	/* settings */
	int samprate;
	int channels;
	int headroom;
	double dbgain;
	/* derived */
	unsigned int threshold;
	int reltc;
	int rmsatktc;
	int rmsreltc;
	int outfract;
	int outshift;
	/* state */
	int idx;
	int peak_z;
	int rms_z;
	int acc1;
	int acc2;
	unsigned int randsave;
	int delay[512];
	/* release tables */
	int peaktab[256];
	int rmstab[256];
} LIMSTATE;

LIMSTATE *LimiterInit(int samprate, int channels, int headroom);
void LimiterFree(LIMSTATE *lim);

void LimiterProcess(int *pcmbuf, int nsamples, LIMSTATE *lim);
void LimiterOutput16(int *pcmbuf, short *outbuf, int nsamples, LIMSTATE *lim);

void LimiterSetGain(double dbgain, LIMSTATE *lim);
void LimiterSetRelease(double release, LIMSTATE *lim);

/* delay in sample frames */
int LimiterGetDelay(LIMSTATE *lim);
double LimiterGetAtten(LIMSTATE *lim);

#ifdef __cplusplus
/*extern "C"*/ }
#endif

#endif /* _LIMITER_H_ */