cvsd.rar_better_cvsd_cvsd code_cvsd codec

/* * 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 (sailer@ife.ee.ethz.ch) (HB9JNX/AE4WA) * Swiss Federal Institute of Technology, Electronics Lab * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * * Change History: * * June 1, 1998 - Chris Bagwell (cbagwell@sprynet.com) * Fixed compile warnings reported by Kjetil Torgrim Homme * <kjetilho@ifi.uio.no> * * */ /* ---------------------------------------------------------------------- */ #include "st_i.h" #include <math.h> #include <string.h> #include <time.h> #include <stdio.h> #ifdef HAVE_ERRNO_H #include <errno.h> #endif #ifdef HAVE_UNISTD_H #include <unistd.h> /* For SEEK_* defines if not found in stdio */ #endif #include "cvsdfilt.h" /* ---------------------------------------------------------------------- */ #ifndef HAVE_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 char shreg; unsigned mask; unsigned cnt; } bit; unsigned bytes_written; unsigned cvsd_rate; char swapbits; }; /* ---------------------------------------------------------------------- */ static float float_conv(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_t ft) { struct cvsdpriv *p = (struct cvsdpriv *) ft->priv; p->cvsd_rate = (ft->info.rate <= 24000) ? 16000 : 32000; ft->info.rate = 8000; ft->info.channels = 1; ft->info.size = ST_SIZE_WORD; /* make output format default to words */ ft->info.encoding = ST_ENCODING_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; st_report("cvsd: bit rate %dbit/s, bits from %s\n", p->cvsd_rate, p->swapbits ? "msb to lsb" : "lsb to msb"); } /* ---------------------------------------------------------------------- */ int st_cvsdstartread(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; return (ST_SUCCESS); } /* ---------------------------------------------------------------------- */ int st_cvsdstartwrite(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; return(ST_SUCCESS); } /* ---------------------------------------------------------------------- */ int st_cvsdstopwrite(ft_t ft) { struct cvsdpriv *p = (struct cvsdpriv *) ft->priv; if (p->bit.cnt) { st_writeb(ft, p->bit.shreg); p->bytes_written++; } st_report("cvsd: min slope %f, max slope %f\n", p->com.v_min, p->com.v_max); return (ST_SUCCESS); } /* ---------------------------------------------------------------------- */ int st_cvsdstopread(ft_t ft) { struct cvsdpriv *p = (struct cvsdpriv *) ft->priv; st_report("cvsd: min value %f, max value %f\n", p->com.v_min, p->com.v_max); return(ST_SUCCESS); } /* ---------------------------------------------------------------------- */ #undef DEBUG #ifdef DEBUG static struct { FILE *f1; FILE *f2; int cnt } dbg = { NULL, NULL, 0 }; #endif st_ssize_t st_cvsdread(ft_t ft, st_sample_t *buf, st_ssize_t nsamp) { struct cvsdpriv *p = (struct cvsdpriv *) ft->priv; int done = 0; float oval; #ifdef DEBUG if (!dbg.f1) { if (!(dbg.f1 = fopen("dbg1", "w"))) { st_fail_errno(ft,errno,"debugging"); return (0); } fprintf(dbg.f1, "\"input\"\n"); } if (!dbg.f2) { if (!(dbg.f2 = fopen("dbg2", "w"))) { st_fail_errno(ft,errno,"debugging"); return (0); } fprintf(dbg.f2, "\"recon\"\n"); } #endif while (done