Hello !
Broadcom has a GPL narrowband voice codec who takes 12 mips, 2000 words RAM and 13000 words total memory footprint, on a 16 bit fixed-point DSP.
16 kb/s version called BroadVoice16 (BV16) for narrowband telephone-bandwidth speech sampled at 8 kHz
any chance it can work on a Due, at least the decoder part, to play back voice stored on a SD card ?
http://www.broadcom.com/support/broadvoice/codec_comparison.phpi was thinking about an audio player like this, to diffuse educational audio records to people in developping nations :
http://www.literacybridge.org/talking-book//*****************************************************************************/
/* BroadVoice(R)16 (BV16) Fixed-Point ANSI-C Source Code */
/* Revision Date: October 5, 2012 */
/* Version 1.2 */
/*****************************************************************************/
/*****************************************************************************/
/* Copyright 2000-2012 Broadcom Corporation */
/* */
/* This software is provided under the GNU Lesser General Public License, */
/* version 2.1, as published by the Free Software Foundation ("LGPL"). */
/* This program is distributed in the hope that it will be useful, but */
/* WITHOUT ANY SUPPORT OR WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the LGPL for */
/* more details. A copy of the LGPL is available at */
/* http://www.broadcom.com/licenses/LGPLv2.1.php, */
/* or by writing to the Free Software Foundation, Inc., */
/* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
/*****************************************************************************/
/*****************************************************************************
decoder.c : BV16 Fixed-Point Decoder Main Subroutines
$Log$
******************************************************************************/
#include "typedef.h"
#include "bvcommon.h"
#include "bv16cnst.h"
#include "bv16strct.h"
#include "bv16externs.h"
#include "basop32.h"
#include "utility.h"
#include "mathutil.h"
#include "postfilt.h"
void Reset_BV16_Decoder(struct BV16_Decoder_State *c)
{
int i;
W16zero((Word16 *) c, sizeof(struct BV16_Decoder_State)/sizeof(Word16));
c->lsplast[0] = 3641;
c->lsplast[1] = 7282;
c->lsplast[2] = 10923;
c->lsplast[3] = 14564;
c->lsplast[4] = 18204;
c->lsplast[5] = 21845;
c->lsplast[6] = 25486;
c->lsplast[7] = 29127;
c->pp_last = 50;
c->lmax = MIN_32;
c->lmin = MAX_32;
c->lmean = 419430400; /* 12.5 Q25 */
c->x1 = 570425344; /* 17.0 Q25 */
c->level = 570425344; /* 17.0 Q25 */
c->ngfae = LGPORDER+1;
c->nggalgc = Nfdm+1;
c->estl_alpha_min = estl_alpha;
c->idum =0;
c->per = 0;
for(i=0; i<LPCO; i++)
c->atplc[i+1] = 0;
c->ma_a = 0;
c->b_prv[0] = 8192; /* Q13 */
c->b_prv[1] = 0;
c->pp_prv = 100;
}
void BV16_Decode(
struct BV16_Bit_Stream *bs,
struct BV16_Decoder_State *ds,
Word16 *x)
{
Word32 lgq, lg_el;
Word16 gainq; /* Q3 */
Word16 pp;
Word32 a0;
Word16 gain_exp;
Word16 i;
Word16 a0hi, a0lo;
Word16 ltsym[LTMOFF+FRSZ];
Word16 xq[LXQ];
Word16 a[LPCO+1];
Word16 lspq[LPCO]; /* Q15 */
Word16 cbs[VDIM*CBSZ];
Word16 bq[3]; /* Q15 */
Word32 bss;
Word32 E;
/* set frame erasure flags */
if (ds->cfecount != 0) {
ds->ngfae = 1;
} else {
ds->ngfae++;
if (ds->ngfae>LGPORDER) ds->ngfae=LGPORDER+1;
}
/* reset frame erasure counter */
ds->cfecount = 0;
/* decode pitch period */
pp = (bs->ppidx + MINPP);
/* decode spectral information */
lspdec(lspq,bs->lspidx,ds->lsppm,ds->lsplast);
lsp2a(lspq,a);
W16copy(ds->lsplast, lspq, LPCO);
/* decode pitch taps */
pp3dec(bs->bqidx, bq);
/* decode gain */
a0 = gaindec(&lgq,bs->gidx,ds->lgpm,ds->prevlg,ds->level,
&ds->nggalgc,&lg_el);
/* gain normalization */
gain_exp = sub(norm_l(a0), 2);
/* scale down quantized gain by 1.5, 1/1.5=2/3 (21845 Q15) */
L_Extract(a0, &a0hi, &a0lo);
a0 = Mpy_32_16(a0hi, a0lo, 21845);
gainq = round(L_shl(a0, gain_exp));
/* scale the scalar quantizer codebook to current signal level */
for (i=0;i<(VDIM*CBSZ);i++) cbs[i] = mult_r(gainq, cccb[i]);
/* copy state memory to buffer */
W16copy(xq, ds->xq, XQOFF);
W16copy(ltsym, ds->ltsym, LTMOFF);
/* decoding of the excitation signal with integrated long-term */
/* and short-term synthesis */
excdec_w_synth(xq+XQOFF,ltsym+LTMOFF,ds->stsym,bs->qvidx,bq,cbs,pp,
a,gain_exp,&E);
ds->E = E;
/* update the remaining state memory */
W16copy(ds->ltsym, ltsym+FRSZ, LTMOFF);
W16copy(ds->xq, xq+FRSZ, XQOFF);
ds->pp_last = pp;
W16copy(ds->bq_last, bq, 3);
/* level estimation */
estlevel(lg_el,&ds->level,&ds->lmax,&ds->lmin,&ds->lmean,&ds->x1,
ds->ngfae, ds->nggalgc,&ds->estl_alpha_min);
/* adaptive postfiltering */
postfilter(xq, pp, &(ds->ma_a), ds->b_prv, &(ds->pp_prv), x);
/* scale signal up by 1.5 */
for(i=0; i<FRSZ; i++)
x[i] = add(x[i], shr(x[i],1));
W16copy(ds->atplc, a, LPCO+1);
bss = L_add(L_add(bq[0], bq[1]), bq[2]);
if (bss > 32768)
bss = 32768;
else if (bss < 0)
bss = 0;
ds->per = add(shr(ds->per, 1), (Word16)L_shr(bss, 1));
}
