cvsd.c

linux下录音程序

/*
 *      CVSD (Continuously Variable Slope Delta modulation)
 *      conversion routines
 *
 *      The CVSD format is described in the MIL Std 188 113, which is
 *      available from http://bbs.itsi.disa.mil:5580/T3564
 *
 *	Copyright (C) 1996  
 *      Thomas Sailer ([e-mail]) (HB9JNX/AE4WA)
 *      Swiss Federal Institute of Technology, Electronics Lab
 *
 *	This program is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *
 *	This program is distributed in the hope that it will be useful,
 *	but WITHOUT ANY WARRANTY; without even the implied warranty of
 *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *	GNU General Public License for more details.
 *
 *	You should have received a copy of the GNU General Public License
 *	along with this program; if not, write to the Free Software
 *	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *
 * Change History:
 *
 * June 1, 1998 - Chris Bagwell ([e-mail])
 *   Fixed compile warnings reported by Kjetil Torgrim Homme
 *   <[e-mail]>
 *
 *
 */

/* ---------------------------------------------------------------------- */

#include <limits.h>
#include <math.h>
#include <string.h>
#include <time.h>

#ifndef SEEK_SET
#define SEEK_SET 0		/* nasty nasty */
#endif /* SEEK_SET */

#include "cvsdfilt.h"
#include "st.h"
#include "libst.h"

/* ---------------------------------------------------------------------- */

#ifdef NEED_MEMMOVE
#define memmove(dest,src,len) (bcopy((src),(dest),(len)))
#endif

/* ---------------------------------------------------------------------- */
/*
 * private data structures
 */

struct cvsd_common_state {
	unsigned overload;
	float mla_int;
	float mla_tc0;
	float mla_tc1;
	unsigned phase;
	unsigned phase_inc;
	float v_min, v_max;
};

struct cvsd_decode_state {
	float output_filter[DEC_FILTERLEN];
};

struct cvsd_encode_state {
	float recon_int;
	float input_filter[ENC_FILTERLEN];
};

struct cvsdpriv {
	struct cvsd_common_state com;
	union {
		struct cvsd_decode_state dec;
		struct cvsd_encode_state enc;
	} c;
	struct {
		unsigned shreg;
		unsigned mask;
		unsigned cnt;
	} bit;
	unsigned bytes_written;
	unsigned cvsd_rate;
	char swapbits;
};

/* ---------------------------------------------------------------------- */

float float_conv(fp1, fp2, n)
float *fp1;
float *fp2;
int n;
{
	float res = 0;
	for(; n > 0; n--)
		res += (*fp1++) * (*fp2++);
	return res;
}

/* ---------------------------------------------------------------------- */
/*
 * some remarks about the implementation of the CVSD decoder
 * the principal integrator is integrated into the output filter
 * to achieve this, the coefficients of the output filter are multiplied
 * with (1/(1-1/z)) in the initialisation code.
 * the output filter must have a sharp zero at f=0 (i.e. the sum of the
 * filter parameters must be zero). This prevents an accumulation of
 * DC voltage at the principal integration.
 */
/* ---------------------------------------------------------------------- */

static void cvsdstartcommon(ft)
ft_t ft;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;
	
	/* sanity check */
	if (sizeof(struct cvsdpriv) > PRIVSIZE)
		fail("struct cvsdpriv is too big (%d); change PRIVSIZE in st.h and recompile sox", sizeof(struct cvsdpriv));
	p->cvsd_rate = (ft->info.rate <= 24000) ? 16000 : 32000;
	ft->info.rate = 8000;
	ft->info.channels = 1;
	ft->info.size = WORD; /* make output format default to words */
	ft->info.style = SIGN2;
	p->swapbits = ft->swap;
	ft->swap = 0;
	/*
	 * initialize the decoder
	 */
	p->com.overload = 0x5;
	p->com.mla_int = 0;
	/*
	 * timeconst = (1/e)^(200 / SR) = exp(-200/SR)
	 * SR is the sampling rate
	 */
	p->com.mla_tc0 = exp((-200.0)/((float)(p->cvsd_rate)));
	/*
	 * phase_inc = 32000 / SR
	 */
	p->com.phase_inc = 32000 / p->cvsd_rate;
	/*
	 * initialize bit shift register
	 */
	p->bit.shreg = p->bit.cnt = 0;
	p->bit.mask = p->swapbits ? 0x80 : 1;
	/*
	 * count the bytes written
	 */
	p->bytes_written = 0;
	p->com.v_min = 1;
	p->com.v_max = -1;
	report("cvsd: bit rate %dbit/s, bits from %s\n", p->cvsd_rate,
	       p->swapbits ? "msb to lsb" : "lsb to msb");
}

/* ---------------------------------------------------------------------- */

void cvsdstartread(ft) 
ft_t ft;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;
	float *fp1;
	int i;
	
	cvsdstartcommon(ft);
	p->com.mla_tc1 = 0.1 * (1 - p->com.mla_tc0);
	p->com.phase = 0;
	/*
	 * initialize the output filter coeffs (i.e. multiply
	 * the coeffs with (1/(1-1/z)) to achieve integration
	 * this is now done in the filter parameter generation utility
	 */
	/*
	 * zero the filter 
	 */
	for(fp1 = p->c.dec.output_filter, i = DEC_FILTERLEN; i > 0; i--)
		*fp1++ = 0;
}

/* ---------------------------------------------------------------------- */

void cvsdstartwrite(ft) 
ft_t ft;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;
	float *fp1;
	int i;

	cvsdstartcommon(ft);
	p->com.mla_tc1 = 0.1 * (1 - p->com.mla_tc0);
	p->com.phase = 4;
	/*
	 * zero the filter 
	 */
	for(fp1 = p->c.enc.input_filter, i = ENC_FILTERLEN; i > 0; i--)
		*fp1++ = 0;
	p->c.enc.recon_int = 0;
}

/* ---------------------------------------------------------------------- */

void
cvsdstopwrite(ft)
ft_t ft;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;

	if (p->bit.cnt) {
		putc(p->bit.shreg, ft->fp);
		p->bytes_written++;
	}
	report("cvsd: min slope %f, max slope %f\n", 
	       p->com.v_min, p->com.v_max);	
}

/* ---------------------------------------------------------------------- */

void
cvsdstopread(ft)
ft_t ft;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;

	report("cvsd: min value %f, max value %f\n", 
	       p->com.v_min, p->com.v_max);
}

/* ---------------------------------------------------------------------- */

#undef DEBUG

#ifdef DEBUG
static struct {
	FILE *f1;
	FILE *f2;
	int cnt
} dbg = { NULL, NULL, 0 };
#endif

LONG cvsdread(ft, buf, nsamp) 
ft_t ft;
LONG *buf, nsamp;
{
	struct cvsdpriv *p = (struct cvsdpriv *) ft->priv;
	int done = 0;
	float oval;
	
#ifdef DEBUG
	if (!dbg.f1) {
		if (!(dbg.f1 = fopen("dbg1", "w")))
			fail("debugging");
		fprintf(dbg.f1, "\"input\"\n");
	}
	if (!dbg.f2) {
		if (!(dbg.f2 = fopen("dbg2", "w")))
			fail("debugging");
		fprintf(dbg.f2, "\"recon\"\n");
	}
#endif
	while (done < nsamp) {
		if (!p->bit.cnt) {
			p->bit.shreg = getc(ft->fp);
			if (feof(ft->fp))
				return done;
			p->bit.cnt = 8;
			p->bit.mask = p->swapbits ? 0x80 : 1;
		}
		/*
		 * handle one bit
		 */
		p->bit.cnt--;
		p->com.overload = ((p->com.overload << 1) | 
				   (!!(p->bit.shreg & p->bit.mask))) & 7;
		if (p->swapbits)
			p->bit.mask >>= 1;
		else
			p->bit.mask <<= 1;
		p->com.mla_int *= p->com.mla_tc0;
		if ((p->com.overload == 0) || (p->com.overload == 7))
			p->com.mla_int += p->com.mla_tc1;
		memmove(p->c.dec.output_filter+1, p->c.dec.output_filter,
			sizeof(p->c.dec.output_filter)-sizeof(float));
		if (p->com.overload & 1)
			p->c.dec.output_filter[0] = p->com.mla_int;
		else
			p->c.dec.output_filter[0] = -p->com.mla_int;
		/*
		 * check if the next output is due
		 */
		p->com.phase += p->com.phase_inc;
		if (p->com.phase >= 4) {
			oval = float_conv(p->c.dec.output_filter, 
					  (p->cvsd_rate < 24000) ? 
					  dec_filter_16 : dec_filter_32, 
					  DEC_FILTERLEN);
#ifdef DEBUG
			fprintf(dbg.f1, "%f %f\n", (double)dbg.cnt, 
				(double)p->com.mla_int);
			fprintf(dbg.f2, "%f %f\n", (double)dbg.cnt, 
				(double)oval);
			dbg.cnt++;
#endif		
			if (oval > p->com.v_max)
				p->com.v_max = oval;
			if (oval < p->com.v_min)
				p->com.v_min = oval;
			*buf++ = (oval * ((float)LONG_MAX));
			done++;
		}