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LPC10-15 2.4Kpbs语音压缩定点运算C语言源程序在2003年我接触ACCFast的mp3方案，其有Celp 4.8K的语音压缩录音，但是录音的效果一直非常差，在我看来其dsp的速度可以达到100M以上，内存空间也足够大，为什么效果非常差了。最近，由于工程的需要，我们急切需要一个压缩率低的，音质可以接受的压缩编码。这有两上原因，1.mcu的运算速度不高，内存变量空间很少;2.用于无线距离传输，可以使用传输速率低的RF传输，这样出错受干扰的可能性较少。于是我开始留意网上的2.4k的源程序。结果好多都是收费的，我试着在国外的网站找找，结果在网站
找到了源程序，还是定点运算。这个时候我才想起当初Accfast的录音音质差的原因，就是没有处理好定点与浮点运算。此外，我把这一段时间收集的资料，包括lpc10-15, 对”LPC-10编码算法的分析与改进.pdf”, “简化的LPC-10语音编码算法研究与仿真.pdf”, HawkVoiceDI091src.zip, openlpc.fp.zip，lpc10-25s.wav(2.4k的压缩效果)，一些文章压缩成一个rar,有需要的朋友请到：
下载我过一段时间会把它的程序进行简化，到时再与大家分享.
其源程序：
Openlpc.h:
/*
* LPC subroutine declarations
*/
#ifndef OPENLPC_H
#define OPENLPC_H
#ifdef __cplusplus
extern "C" {
#endif
#define OPENLPC_FRAMESIZE_1_8 250
#define OPENLPC_FRAMESIZE_1_4 320
#define OPENLPC_ENCODED_FRAME_SIZE 7
typedef struct openlpc_e_state openlpc_encoder_state;
typedef struct openlpc_d_state openlpc_decoder_state;
openlpc_encoder_state *create_openlpc_encoder_state(void);
void init_openlpc_encoder_state(openlpc_encoder_state *st, int framelen);
int openlpc_encode(const short *in, unsigned char *out, openlpc_encoder_state *st);
void destroy_openlpc_encoder_state(openlpc_encoder_state *st);
openlpc_decoder_state *create_openlpc_decoder_state(void);
void init_openlpc_decoder_state(openlpc_decoder_state *st, int framelen);
int openlpc_decode(unsigned char *in, short *out, openlpc_decoder_state *st);
void destroy_openlpc_decoder_state(openlpc_decoder_state *st);
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* OPENLPC_H */
Openlpc.fix.c:
/*
Fixed point OpenLPC codec
Copyright (C) 2003-2005 Phil Frisbie, Jr. (phil@hawksoft.com)
This is a major rewrite of the orginal floating point OpenLPC
code from Future Dynamics. As such, a copywrite notice is not
required to credit Future Dynamics.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library 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.
Or go to
*/
/************************************************************************
Low bitrate LPC CODEC derived from the public domain implementation
of Ron Frederick.
The basic design is preserved, except for several bug fixes and
the following modifications:
1. The pitch detector operates on the (downsampled) signal, not on
the residue. This appears to yield better performances, and it
lowers the processing load.
2. Each frame is elongated by 50% prefixing it with the last half
of the previous frame. This design, inherited from the original
code for windowing purposes, is exploited in order to provide
two independent pitch analyses: on the first 2/3, and on the
second 2/3 of the elongated frame (of course, they overlap by
half):
last half old frame new frame
--------------------========================================
<--------- first pitch region --------->
<--------- second pitch region ------->
Two voiced/unvoiced flags define the voicing status of each
region; only one value for the period is retained (if both
halves are voiced, the average is used).
The two flags are used by the synthesizer for the halves of
each frame to play back. Of course, this is non optimal but
is good enough (a half-frame would be too short for measuring
low pitches)
3. The parameters (one float for the period (pitch), one for the
gain, and ten for the LPC-10 filter) are quantized according
this procedure:
- the period is logarithmically compressed, then quantized
as 8-bit unsigned int (6 would actually suffice)
- the gain is logarithmically compressed (using a different
formula), then quantized at 6-bit unsigned int. The two
remaining bits are used for the voicing flags.
- the first two LPC parameters (k[1] and k[2]) are multiplied
by PI/2, and the arcsine of the result is quantized as
6 and 5 bit signed integers. This has proved more effective
than the log-area compression used by LPC-10.
- the remaining eight LPC parameters (k[3]...k[10]) are
quantized as, respectively, 5,4,4,3,3,3,3 and 2 bit signed
integers.
Finally, period and gain plus voicing flags are stored in the
first two bytes of the 7-byte parameters block, and the quantized
LPC parameters are packed into the remaining 5 bytes. Two bits
remain unassigned, and can be used for error detection or other
purposes.
The frame lenght is actually variable, and is simply passed as
initialization parameter to lpc_init(): this allows to experiment
with various frame lengths. Long frames reduce the bitrate, but
exceeding 320 samples (i.e. 40 ms, at 8000 samples/s) tend to
deteriorate the speech, that sounds like spoken by a person
affected by a stroke: the LPC parameters (modeling the vocal
tract) can't change fast enough for a natural-sounding synthesis.
25 ms per frame already yields a quite tight compression, corresponding
to 1000/40 * 7 * 8 = 1400 bps. The quality improves little with
frames shorter than 250 samples (32 frames/s), so this is a recommended
compromise. The bitrate is 32 * 7 * 8 = 1792 bps.
The synthesizer has been modified as well. For voiced subframes it
now uses a sawtooth excitation, instead of the original pulse train.
This idea, copied from MELP, reduces the buzzing-noise artifacts.
In order to compensate the non-white spectrum of the sawtooth, a
pre-emphasis is applied to the signal before the Durbin calculation.
The filter has (in s-space) two zeroes at (640, 0) Hz and two poles
at (3200, 0) Hz. These filters have been handoded, and may not be
optimal. Two other filters (anti-hum high-pass with corner at 100 Hz,
and pre-downsampling lowpass with corner at 300 Hz) are Butterworth
designs produced by the MkFilter package by A.J. Fisher
().
\************************************************************************/
#ifdef _MSC_VER
#pragma warning (disable:4711) /* to disable automatic inline warning */
#define M_PI (3.1415926535897932384626433832795)
#endif
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include <math.h>
#include "openlpc.h"
#define fixed32 long
#if defined WIN32 || defined WIN64 || defined (_WIN32_WCE)
#define fixed64 __int64
#else
#define fixed64 long long
#endif
/* These are for development and debugging and should not be changed unless
you REALLY know what you are doing ;) */
#define IGNORE_OVERFLOW
#define FAST_FILTERS
#define PRECISION 20
#define ftofix32(x) ((fixed32)((x) * (float)(1 < < PRECISION) + ((x) < 0 ? -0.5 : 0.5)))
#define itofix32(x) ((x) < < PRECISION)
#define fixtoi32(x) ((x) > > PRECISION)
#define fixtof32(x) (float)((float)(x) / (float)(1 < < PRECISION))
static fixed32 fixmul32(fixed32 x, fixed32 y)
{
fixed64 temp;
temp = x;
temp *= y;
temp > > = PRECISION;
#ifndef IGNORE_OVERFLOW
if(temp > 0x7fffffff)
{
return 0x7fffffff;
}
else if(temp < -0x7ffffffe)
{
return -0x7ffffffe;
}
#endif
return (fixed32)temp;
}
static fixed32 fixdiv32(fixed32 x, fixed32 y)
{
fixed64 temp;
if(x == 0)
return 0;
if(y == 0)
return 0x7fffffff;
temp = x;
temp < <= PRECISION;
return (fixed32)(temp / y);
}
static fixed32 fixsqrt32(fixed32 x)
{
unsigned long r = 0, s, v = (unsigned long)x;
#define STEP(k) s = r + (1 < < k * 2); r > > = 1; if (s <= v) { v -= s; r |= (1 < < k * 2); }
STEP(15);
STEP(14);
STEP(13);
STEP(12);
STEP(11);
STEP(10);
STEP(9);
STEP(8);
STEP(7);
STEP(6);
STEP(5);
STEP(4);
STEP(3);
STEP(2);
STEP(1);
STEP(0);
return (fixed32)(r < < (PRECISION / 2));
}
__inline static fixed32 fixexp32(fixed32 x)
{
fixed64 result = ftofix32(1.f);
fixed64 temp;
int sign = 1;
/* reduce range to 0.0 to 1.0 */
if(x < 0)
{
x = (fixed32)-x;
sign = -1;
}
while(x > itofix32(1))
{
x -= itofix32(1);
result *= ftofix32(2.718282f);
result > > = PRECISION;
}
/* reduce range to 0.0 to 0.5 */
if(x > ftofix32(0.5f))
{
x -= ftofix32(0.5f);
result *= ftofix32(1.648721f);
result > > = PRECISION;
}
if(result > 0x7fffffff)
{
return 0x7fffffff;
}
temp = ftofix32(0.00138888f) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(0.00833333f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(0.04166666f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(0.16666666f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(0.5f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(1.0f)) * x;
temp > > = PRECISION;
result *= (temp + ftofix32(1.f));
result > > = PRECISION;
if(sign == -1)
{
temp = 1;
result = (temp < < (PRECISION * 2)) / result;
}
if(result > 0x7fffffff)
{
return 0x7fffffff;
}
return (fixed32)result;
}
__inline static fixed32 fixlog32(fixed32 x)
{
fixed64 result = 0;
fixed64 temp;
if(x == 0)
{
return -0x7ffffffe;
}
else if(x < 0)
{
return 0;
}
while(x > itofix32(2))
{
result += ftofix32(0.693147f);
x /= 2;
}
while(x < itofix32(1))
{
result -= ftofix32(0.693147f);
x *= 2;
}
x -= itofix32(1);
temp = ftofix32(-.0064535442f) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.0360884937f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.0953293897f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.1676540711f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.2407338084f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.3317990258f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.4998741238f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.9999964239f)) * x;
temp > > = PRECISION;
result += temp;
return (fixed32)result;
}
__inline fixed32 fixsin32(fixed32 x)
{
fixed64 x2, temp;
int sign = 1;
if(x < 0)
{
sign = -1;
x = -x;
}
while(x > ftofix32(M_PI))
{
x -= ftofix32(M_PI);
sign = -sign;
}
if(x > ftofix32(M_PI/2))
{
x = ftofix32(M_PI) - x;
}
x2 = (fixed64)x * x;
x2 > > = PRECISION;
if(sign != 1)
{
x = -x;
}
temp = ftofix32(-.0000000239f) * x2;
temp > > = PRECISION;
temp = (temp + ftofix32(.0000027526f)) * x2;
temp > > = PRECISION;
temp = (temp - ftofix32(.0001984090f)) * x2;
temp > > = PRECISION;
temp = (temp + ftofix32(.0083333315f)) * x2;
temp > > = PRECISION;
temp = (temp - ftofix32(.1666666664f)) * x2;
temp > > = PRECISION;
temp += itofix32(1);
temp = temp * x;
temp > > = PRECISION;
return (fixed32)(temp);
}
__inline fixed32 fixasin32(fixed32 x)
{
fixed64 temp;
int sign = 1;
if(x > itofix32(1) || x < itofix32(-1))
{
return 0;
}
if(x < 0)
{
sign = -1;
x = -x;
}
temp = 0;
temp = ftofix32(-.0012624911f) * (fixed64)x;
temp > > = PRECISION;
temp = (temp + ftofix32(.0066700901f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.0170881256f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.0308918810f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.0501743046f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(.0889789874f)) * x;
temp > > = PRECISION;
temp = (temp - ftofix32(.2145988016f)) * x;
temp > > = PRECISION;
temp = (temp + ftofix32(1.570796305f)) * fixsqrt32(itofix32(1) - x);
temp > > = PRECISION;
return sign * (ftofix32(M_PI/2) - (fixed32)temp);
}
#define PREEMPH
#define bcopy(a, b, n) memmove(b, a, n)
#define LPC_FILTORDER 10
#define FS 8000.0 /* Sampling rate */
#define MAXWINDOW 1000 /* Max analysis window length */
typedef struct openlpc_e_state{
int framelen, buflen;
fixed32 s[MAXWINDOW], y[MAXWINDOW], h[MAXWINDOW];
fixed32 xv1[3], yv1[3],
xv2[2], yv2[2],
xv3[1], yv3[3],
xv4[2], yv4[2];
fixed32 w[MAXWINDOW], r[LPC_FILTORDER+1];
} openlpc_e_state_t;
typedef struct openlpc_d_state{
fixed32 Oldper, OldG, Oldk[LPC_FILTORDER + 1];
fixed32 bp[LPC_FILTORDER+1];
fixed32 exc;
fixed32 gainadj;
int pitchctr, framelen, buflen;
} openlpc_d_state_t;
#define FC 200.0 /* Pitch analyzer filter cutoff */
#define DOWN 5 /* Decimation for pitch analyzer */
#define MINPIT 40.0 /* Minimum pitch (observed: 74) */
#define MAXPIT 320.0 /* Maximum pitch (observed: 250) */
#define MINPER (int)(FS / (DOWN * MAXPIT) + .5) /* Minimum period */
#define MAXPER (int)(FS / (DOWN * MINPIT) + .5) /* Maximum period */
#define REAL_MINPER (DOWN * MINPER) /* converted to samples units */
#define WSCALE 1.5863 /* Energy loss due to windowing */
#define BITS_FOR_LPC 38
#define ARCSIN_Q /* provides better quantization of first two k[] at low bitrates */
#if BITS_FOR_LPC == 38
/* (38 bit LPC-10, 2.7 Kbit/s @ 20ms, 2.4 Kbit/s @ 22.5 ms */
static int parambits[LPC_FILTORDER] = {6,5,5,4,4,3,3,3,3,2};
#elif BITS_FOR_LPC == 32
/* (32 bit LPC-10, 2.4 Kbit/s, not so good */
static int parambits[LPC_FILTORDER] = {5,5,5,4,3,3,2,2,2,1};
#else /* BITS_FOR_LPC == 80 */
/* 80-bit LPC10, 4.8 Kbit/s */
static int parambits[LPC_FILTORDER] = {8,8,8,8,8,8,8,8,8,8};
#endif
static fixed32 logmaxminper;
static int sizeofparm; /* computed by lpc_init */
static void auto_correl1(fixed32 *w, int n, fixed32 *r)
{
int i, k;
fixed64 temp, temp2;
for (k=0; k <= MAXPER; k++, n--) {
temp = 0;
for (i=0; i < n; i++) {
temp2 = w[i];
temp += temp2 * w[i+k];
}
r[k] = (fixed32)(temp > > PRECISION);
}
}
static void auto_correl2(fixed32 *w, int n, fixed32 *r)
{
int i, k;
fixed64 temp, temp2;
for (k=0; k <= LPC_FILTORDER; k++, n--) {
temp = 0;
for (i=0; i < n; i++) {
temp2 = w[i];
temp += temp2 * w[i+k];
}
r[k] = (fixed32)(temp > > PRECISION);
}
}
static void durbin(fixed32 r[], int p, fixed32 k[], fixed32 *g)
{
int i, j;
fixed32 a[LPC_FILTORDER+1], at[LPC_FILTORDER+1], e;
for (i=0; i <= p; i++)
a[i] = at[i] = 0;
e = r[0];
for (i=1; i <= p; i++) {
k[i] = -r[i];
for (j=1; j < i; j++) {
at[j] = a[j];
k[i] -= fixmul32(a[j], r[i-j]);
}
if (e == 0) { /* fix by John Walker */
*g = 0;
return;
}
k[i] = fixdiv32(k[i], e);
a[i] = k[i];
for (j=1; j < i; j++)
a[j] = at[j] + fixmul32(k[i], at[i-j]);
e = fixmul32(e, (itofix32(1) - fixmul32(k[i], k[i])));
}
if (e < 0) {
e = 0; /* fix by John Walker */
}
*g = fixsqrt32(e);
}
static void calc_pitch(fixed32 w[], int len, fixed32 *per)
{
int i, j, rpos;
fixed32 d[MAXWINDOW / DOWN], r[MAXPER + 1], rmax;
fixed32 rval, rm, rp;
fixed32 x, y;
fixed32 vthresh;
/* decimation */
for (i=0, j=0; i < len; i+=DOWN)
d[j++] = w[i];
auto_correl1(d, len / DOWN, r);
/* find peak between MINPER and MAXPER */
x = itofix32(1);
rpos = 0;
rmax = 0;
for (i = 1; i <= MAXPER; i++) {
rm = r[i-1];
rp = r[i+1];
y = rm+r[i]+rp; /* find max of integral from i-1 to i+1 */
if (y > rmax && r[i] > rm && r[i] > rp && i > MINPER) {
rmax = y;
rpos = i;
}
}
/* consider adjacent values */
rm = r[rpos-1];
rp = r[rpos+1];
if(rpos > 0) {
x = fixdiv32(((rpos-1) * rm + rpos * r[rpos] + (rpos+1) * rp), (rm+r[rpos]+rp));
}
/* normalize, so that 0. < rval < 1. */
rval = (r[0] == 0 ? 0 : fixdiv32(r[rpos], r[0]));
/* periods near the low boundary and at low volumes
are usually spurious and
manifest themselves as annoying mosquito buzzes */
*per = 0; /* default: unvoiced */
if ( x > itofix32(MINPER) && /* x could be < MINPER or even < 0 if rpos == MINPER */
x < itofix32(MAXPER + 1) /* same story */
) {
vthresh = ftofix32(0.6);
if(r[0] > ftofix32(0.002)) /* at low volumes ( < 0.002), prefer unvoiced */
vthresh = ftofix32(0.25); /* drop threshold at high volumes */
if(rval > vthresh)
*per = x * DOWN;
}
}
/* Initialization of various parameters */
openlpc_encoder_state *create_openlpc_encoder_state(void)
{
openlpc_encoder_state *state;
state = (openlpc_encoder_state *)malloc(sizeof(openlpc_encoder_state));
return state;
}
void init_openlpc_encoder_state(openlpc_encoder_state *st, int framelen)
{
int i, j;
st-> framelen = framelen;
memset(st-> y, 0, sizeof(st-> y));
st-> buflen = framelen * 3 / 2;
/* (st-> buflen > MAXWINDOW) return -1;*/
for(i=0, j=0; i <sizeof(parambits)/sizeof(parambits[0]); i++) {
j += parambits[i];
}
sizeofparm = (j + 7) / 8 + 2;
for (i = 0; i < st-> buflen; i++) {
st-> s[i] = 0;
/* this is only calculated once, but used each frame, */
/* so we will use floating point for accuracy */
st-> h[i] = ftofix32(WSCALE*(0.54 - 0.46 * cos(2 * M_PI * i / (st-> buflen-1.0))));
}
/* init the filters */
st-> xv1[0] = st-> xv1[1] = st-> xv1[2] = st-> yv1[0] = st-> yv1[1] = st-> yv1[2] = 0;
st-> xv2[0] = st-> xv2[1] = st-> yv2[0] = st-> yv2[1] = 0;
st-> xv3[0] = st-> yv3[0] = st-> yv3[1] = st-> yv3[2] = 0;
st-> xv4[0] = st-> xv4[1] = st-> yv4[0] = st-> yv4[1] = 0;
logmaxminper = fixlog32(fixdiv32(itofix32(MAXPER), itofix32(MINPER)));
}
void destroy_openlpc_encoder_state(openlpc_encoder_state *st)
{
if(st != NULL)
{
free(st);
st = NULL;
}
}
/* LPC Analysis (compression) */
int openlpc_encode(const short *buf, unsigned char *parm, openlpc_encoder_state *st)
{
int i, j;
fixed32 per, gain, k[LPC_FILTORDER+1];
fixed32 per1, per2;
fixed32 xv10, xv11, xv12, yv10, yv11, yv12, xv30, yv30, yv31, yv32;
#ifdef PREEMPH
fixed32 xv20, xv21, yv20, yv21, xv40, xv41, yv40, yv41;
#endif
xv10 = st-> xv1[0];
xv11 = st-> xv1[1];
xv12 = st-> xv1[2];
yv10 = st-> yv1[0];
yv11 = st-> yv1[1];
yv12 = st-> yv1[2];
xv30 = st-> xv3[0];
yv30 = st-> yv3[0];
yv31 = st-> yv3[1];
yv32 = st-> yv3[2];
/* convert short data in buf[] to signed lin. data in s[] and prefilter */
for (i=0, j=st-> buflen - st-> framelen; i < st-> framelen; i++, j++) {
/* special handling here for the intitial conversion */
fixed32 u = (fixed32)(buf[i] < < (PRECISION - 15));
/* Anti-hum 2nd order Butterworth high-pass, 100 Hz corner frequency */
/* Digital filter designed by mkfilter/mkshape/gencode A.J. Fisher
mkfilter -Bu -Hp -o 2 -a 0.0125 -l -z */
xv10 = xv11;
xv11 = xv12;
#ifdef FAST_FILTERS
xv12 = ((u * 15) > > 4) + (u > > 7) + ((u * 11) > > 14); /* /GAIN */
yv10 = yv11;
yv11 = yv12;
yv12 = (fixed32)((xv10 + xv12) - (xv11 + xv11)
- ((yv10 * 7) > > 3) - ((yv10 * 5) > > 8)
+ ((yv11 * 15) > > 3) + (yv11 > > 6) );
#else
xv12 = fixmul32(u, ftofix32(0.94597831)); /* /GAIN */
yv10 = yv11;
yv11 = yv12;
yv12 = (fixed32)((xv10 + xv12) - (xv11 + xv11)
+ fixmul32(ftofix32(-0.8948742499), yv10) + fixmul32(ftofix32(1.8890389823), yv11));
#endif
u = st-> s[j] = yv12; /* also affects input of next stage, to the LPC filter synth */
/* low-pass filter s[] -> y[] before computing pitch */
/* second-order Butterworth low-pass filter, corner at 300 Hz */
/* Digital filter designed by mkfilter/mkshape/gencode A.J. Fisher
MKFILTER.EXE -Bu -Lp -o 2 -a 0.0375 -l -z */
#ifdef FAST_FILTERS
xv30 = ((u * 3) > > 6) + (u > > 13); /* GAIN */
yv30 = yv31;
yv31 = yv32;
yv32 = xv30 - ((yv30 * 23) > > 5) + (yv30 > > 9)
+ ((yv31 * 107) > > 6) - (yv31 > > 9);
#else
xv30 = fixmul32(u, ftofix32(0.04699658)); /* GAIN */
yv30 = yv31;
yv31 = yv32;
yv32 = xv30 + fixmul32(ftofix32(-0.7166152306), yv30) + fixmul32(ftofix32(1.6696186545), yv31);
#endif
st-> y[j] = yv32;
}
st-> xv1[0] = xv10;
st-> xv1[1] = xv11;
st-> xv1[2] = xv12;
st-> yv1[0] = yv10;
st-> yv1[1] = yv11;
st-> yv1[2] = yv12;
st-> xv3[0] = xv30;
st-> yv3[0] = yv30;
st-> yv3[1] = yv31;
st-> yv3[2] = yv32;
#ifdef PREEMPH
/* operate optional preemphasis s[] -> s[] on the newly arrived frame */
xv20 = st-> xv2[0];
xv21 = st-> xv2[1];
yv20 = st-> yv2[0];
yv21 = st-> yv2[1];
xv40 = st-> xv4[0];
xv41 = st-> xv4[1];
yv40 = st-> yv4[0];
yv41 = st-> yv4[1];
for (j=st-> buflen - st-> framelen; j < st-> buflen; j++) {
fixed32 u = st-> s[j];
/* handcoded filter: 1 zero at 640 Hz, 1 pole at 3200 */
#define TAU (FS / 3200.f)
#define RHO (0.1f)
xv20 = xv21; /* e(n-1) */
#ifdef FAST_FILTERS
xv21 = ((u * 3) > > 1) +((u * 43) > > 9); /* e(n) , add 4 dB to compensate attenuation */
yv20 = yv21;
yv21 = ((yv20 * 11) > > 4) + ((yv20 * 7) > > 10) /* u(n) */
+ ((xv21 * 23) > > 5) + ((xv21 * 7) > > 11)
- ((xv20 * 11) > > 4) - ((xv20 * 7) > > 10);
#else
xv21 = fixmul32(u, ftofix32(1.584)); /* e(n) , add 4 dB to compensate attenuation */
yv20 = yv21;
yv21 = fixmul32(ftofix32(TAU/(1.0f+RHO+TAU)), yv20) /* u(n) */
+ fixmul32(ftofix32((RHO+TAU)/(1.0f+RHO+TAU)), xv21)
- fixmul32(ftofix32(TAU/(1.0f+RHO+TAU)), xv20);
#endif
u = yv21;
/* cascaded copy of handcoded filter: 1 zero at 640 Hz, 1 pole at 3200 */
xv40 = xv41;
#ifdef FAST_FILTERS
xv41 = ((u * 3) > > 1) +((u * 43) > > 9); /* e(n) , add 4 dB to compensate attenuation */
yv40 = yv41;
yv41 = ((yv40 * 11) > > 4) + ((yv40 * 7) > > 10) /* u(n) */
+ ((xv41 * 23) > > 5) + ((xv41 * 7) > > 11)
- ((xv40 * 11) > > 4) - ((xv40 * 7) > > 10);
#else
xv41 = fixmul32(u, ftofix32(1.584));
yv40 = yv41;
yv41 = fixmul32(ftofix32(TAU/(1.0f+RHO+TAU)), yv40)
+ fixmul32(ftofix32((RHO+TAU)/(1.0f+RHO+TAU)), xv41)
- fixmul32(ftofix32(TAU/(1.0f+RHO+TAU)), xv40);
#endif
u = yv41;
st-> s[j] = u;
}
st-> xv2[0] = xv20;
st-> xv2[1] = xv21;
st-> yv2[0] = yv20;
st-> yv2[1] = yv21;
st-> xv4[0] = xv40;
st-> xv4[1] = xv41;
st-> yv4[0] = yv40;
st-> yv4[1] = yv41;
#endif
/* operate windowing s[] -> w[] */
for (i=0; i < st-> buflen; i++)
st-> w[i] = fixmul32(st-> s[i], st-> h[i]);
/* compute LPC coeff. from autocorrelation (first 11 values) of windowed data */
auto_correl2(st-> w, st-> buflen, st-> r);
durbin(st-> r, LPC_FILTORDER, k, &gain);
/* calculate pitch */
calc_pitch(st-> y, st-> framelen, &per1); /* first 2/3 of buffer */
calc_pitch(st-> y + st-> buflen - st-> framelen, st-> framelen, &per2); /* last 2/3 of buffer */
if(per1 > 0 && per2 > 0)
per = (per1+per2) / 2;
else if(per1 > 0)
per = per1;
else if(per2 > 0)
per = per2;
else
per = 0;
/* logarithmic q.: 0 = MINPER, 256 = MAXPER */
parm[0] = (unsigned char)(per == 0? 0 : (unsigned char)fixtoi32(fixdiv32(fixlog32(fixdiv32(per, itofix32(REAL_MINPER))), logmaxminper) * 256));
#ifdef LINEAR_G_Q
i = fixtoi32(gain * 128);
if(i > 255)
i = 255;
#else
i = fixtoi32(256 * fixlog32(itofix32(1) + fixmul32(ftofix32((2.718-1.f)/10.f), gain))); /* deriv = 5.82 allowing to reserve 2 bits */
if(i > 255) i = 255; /* reached when gain = 10 */
i = (i+2) & 0xfc;
#endif
parm[1] = (unsigned char)i;
if(per1 > 0)
parm[1] |= 1;
if(per2 > 0)
parm[1] |= 2;
for(j=2; j < sizeofparm; j++)
parm[j] = 0;
for (i=0; i < LPC_FILTORDER; i++) {
int bitamount = parambits[i];
int bitc8 = 8-bitamount;
int q = (1 < < bitc8); /* quantum: 1, 2, 4... */
fixed32 u = k[i+1];
int iu;
#ifdef ARCSIN_Q
if(i < 2) u = fixmul32(fixasin32(u), ftofix32(2.f/M_PI));
#endif
u *= 127;
if(u < 0)
u += ftofix32(0.6) * q;
else
u += ftofix32(0.4) * q; /* highly empirical! */
iu = fixtoi32(u);
iu = iu & 0xff; /* keep only 8 bits */
/* make room at the left of parm array shifting left */
for(j=sizeofparm-1; j > = 3; j--) {
parm[j] = (unsigned char)((parm[j] < < bitamount) | (parm[j-1] > > bitc8));
}
parm[2] = (unsigned char)((parm[2] < < bitamount) | (iu > > bitc8)); /* parm[2] */
}
bcopy(st-> s + st-> framelen, st-> s, (st-> buflen - st-> framelen)*sizeof(st-> s[0]));
bcopy(st-> y + st-> framelen, st-> y, (st-> buflen - st-> framelen)*sizeof(st-> y[0]));
return sizeofparm;
}
openlpc_decoder_state *create_openlpc_decoder_state(void)
{
openlpc_decoder_state *state;
state = (openlpc_decoder_state *)malloc(sizeof(openlpc_decoder_state));
return state;
}
void init_openlpc_decoder_state(openlpc_decoder_state *st, int framelen)
{
int i, j;
st-> Oldper = 0;
st-> OldG = 0;
for (i = 0; i <= LPC_FILTORDER; i++) {
st-> Oldk[i] = 0;
st-> bp[i] = 0;
}
st-> pitchctr = 0;
st-> exc = 0;
logmaxminper = fixlog32(fixdiv32(itofix32(MAXPER), itofix32(MINPER)));
for(i=0, j=0; i <sizeof(parambits) / sizeof(parambits[0]); i++) {
j += parambits[i];
}
sizeofparm = (j + 7) / 8 + 2;
/* test for a valid frame len? */
st-> framelen = framelen;
st-> buflen = framelen * 3 / 2;
st-> gainadj = fixsqrt32(itofix32(3) / st-> buflen);
}
#define MIDTAP 1
#define MAXTAP 4
static short y[MAXTAP+1]={-21161, -8478, 30892,-10216, 16950};
static int j=MIDTAP, k=MAXTAP;
__inline int random16 (void)
{
int the_random;
y[k] = (short)(y[k] + y[j]);
the_random = y[k];
k--;
if (k < 0) k = MAXTAP;
j--;
if (j < 0) j = MAXTAP;
return(the_random);
}
/* LPC Synthesis (decoding) */
int openlpc_decode(unsigned char *parm, short *buf, openlpc_decoder_state *st)
{
int i, j, flen=st-> framelen;
fixed32 per, gain, k[LPC_FILTORDER+1];
fixed32 u, NewG, Ginc, Newper, perinc;
fixed32 Newk[LPC_FILTORDER+1], kinc[LPC_FILTORDER+1];
fixed32 gainadj;
int hframe;
fixed32 hper[2];
int ii;
fixed32 bp0, bp1, bp2, bp3, bp4, bp5, bp6, bp7, bp8, bp9, bp10;
fixed32 stgain;
bp0 = st-> bp[0];
bp1 = st-> bp[1];
bp2 = st-> bp[2];
bp3 = st-> bp[3];
bp4 = st-> bp[4];
bp5 = st-> bp[5];
bp6 = st-> bp[6];
bp7 = st-> bp[7];
bp8 = st-> bp[8];
bp9 = st-> bp[9];
bp10 = st-> bp[10];
stgain = st-> gainadj;
per = itofix32(parm[0]);
per = (fixed32)(per == 0? 0: REAL_MINPER * fixexp32(fixmul32(per/256, logmaxminper)));
hper[0] = hper[1] = per;
if((parm[1] & 0x1) == 0) hper[0] = 0;
if((parm[1] & 0x2) == 0) hper[1] = 0;
#ifdef LINEAR_G_Q
gain = itofix32(parm[1]) / 128;
#else
gain = itofix32(parm[1]) / 256;
gain = fixdiv32((fixexp32(gain) - itofix32(1)), ftofix32((2.718-1.f)/10));
#endif
k[0] = 0;
for (i=LPC_FILTORDER-1; i > = 0; i--) {
int bitamount = parambits[i];
int bitc8 = 8-bitamount;
/* casting to char should set the sign properly */
char c = (char)(parm[2] < < bitc8);
for(j=2; j <sizeofparm; j++)
parm[j] = (unsigned char)((parm[j] > > bitamount) | (parm[j+1] < < bitc8));
k[i+1] = itofix32(c) / 128;
#ifdef ARCSIN_Q
if(i <2) k[i+1] = fixsin32(fixmul32(ftofix32(M_PI/2), k[i+1]));
#endif
}
/* k[] are the same in the two subframes */
for (i=1; i <= LPC_FILTORDER; i++) {
Newk[i] = st-> Oldk[i];
kinc[i] = (k[i] - st-> Oldk[i]) / flen;
}
/* Loop on two half frames */
for(hframe=0, ii=0; hframe <2; hframe++) {
Newper = st-> Oldper;
NewG = st-> OldG;
Ginc = (gain - st-> OldG) / (flen / 2);
per = hper[hframe];
if (per == 0) { /* if unvoiced */
gainadj = stgain;
} else {
gainadj = fixsqrt32(per / st-> buflen);
}
/* Interpolate period ONLY if both old and new subframes are voiced, gain and K always */
if (st-> Oldper != 0 && per != 0) {
perinc = (per - st-> Oldper) / (flen / 2);
} else {
perinc = 0;
Newper = per;
}
if (Newper == 0) st-> pitchctr = 0;
for (i=0; i < flen / 2; i++, ii++) {
fixed32 kj;
if (Newper == 0) {
u = fixmul32((random16() < < (PRECISION - 15 - 1)), fixmul32(NewG, gainadj));
} else { /* voiced: send a delta every per samples */
/* triangular excitation */
if (st-> pitchctr == 0) {
st-> exc = fixmul32(NewG, gainadj > > 2);
st-> pitchctr = fixtoi32(Newper);
} else {
st-> exc -= fixmul32(fixdiv32(NewG, Newper), gainadj > > 1);
st-> pitchctr--;
}
u = st-> exc;
}
/* excitation */
kj = Newk[10];
u -= fixmul32(kj, bp9);
bp10 = bp9 + fixmul32(kj, u);
kj = Newk[9];
u -= fixmul32(kj, bp8);
bp9 = bp8 + fixmul32(kj, u);
kj = Newk[8];
u -= fixmul32(kj, bp7);
bp8 = bp7 + fixmul32(kj, u);
kj = Newk[7];
u -= fixmul32(kj, bp6);
bp7 = bp6 + fixmul32(kj, u);
kj = Newk[6];
u -= fixmul32(kj, bp5);
bp6 = bp5 + fixmul32(kj, u);
kj = Newk[5];
u -= fixmul32(kj, bp4);
bp5 = bp4 + fixmul32(kj, u);
kj = Newk[4];
u -= fixmul32(kj, bp3);
bp4 = bp3 + fixmul32(kj, u);
kj = Newk[3];
u -= fixmul32(kj, bp2);
bp3 = bp2 + fixmul32(kj, u);
kj = Newk[2];
u -= fixmul32(kj, bp1);
bp2 = bp1 + fixmul32(kj, u);
kj = Newk[1];
u -= fixmul32(kj, bp0);
bp1 = bp0 + fixmul32(kj, u);
bp0 = u;
if (u < ftofix32(-0.9999)) {
u = ftofix32(-0.9999);
} else if (u > ftofix32(0.9999)) {
u = ftofix32(0.9999);
}
buf[ii] = (short)(u > > (PRECISION - 15));
Newper += perinc;
NewG += Ginc;
for (j=1; j <= LPC_FILTORDER; j++) Newk[j] += kinc[j];
}
st-> Oldper = per;
st-> OldG = gain;
}
st-> bp[0] = bp0;
st-> bp[1] = bp1;
st-> bp[2] = bp2;
st-> bp[3] = bp3;
st-> bp[4] = bp4;
st-> bp[5] = bp5;
st-> bp[6] = bp6;
st-> bp[7] = bp7;
st-> bp[8] = bp8;
st-> bp[9] = bp9;
st-> bp[10] = bp10;
for (j=1; j <= LPC_FILTORDER; j++) st-> Oldk[j] = k[j];
return flen;
}
void destroy_openlpc_decoder_state(openlpc_decoder_state *st)
{
if(st != NULL)
{
free(st);
st = NULL;
}
}