ADPCM的高手救救我吧!!!!! ADPCM 算法那里有 请指路 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 struct adpcm_state { short valprev; /* Previous output value */ char index; /* Index into stepsize table */};class G721 // ADPCM codec{public: G721(); ~G721(); void adpcm_coder(short* indata,char* outdata,int len, adpcm_state* state); void adpcm_decoder(char* indata,short* outdata,int len, adpcm_state* state);};// adpcm.cpp#include "stdafx.h"#include "adpcm.h"//#include "stdio.h" static int indexTable[16] = { -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8,};static int stepsizeTable[89] = { 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 19, 21, 23, 25, 28, 31, 34, 37, 41, 45, 50, 55, 60, 66, 73, 80, 88, 97,107,118, 130,143,157,173,190,209,230,253,279,307, 337,371,408,449,494,544,598,658,724,796, 876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484, 7132, 7845, 8630, 9493,10442,11487,12635,13899, 15289,16818,18500,20350,22385,24623,27086,29794,32767};G721::~G721(){ }G721::G721(){} void G721::adpcm_coder(short* indata,char* outdata,int len,adpcm_state* state){ short *inp; /* Input buffer pointer */ signed char *outp; /* output buffer pointer */ int val; /* Current input sample value */ int sign; /* Current adpcm sign bit */ int delta; /* Current adpcm output value */ int diff; /* Difference between val and valprev */ int step; /* Stepsize */ int valpred; /* Predicted output value */ int vpdiff; /* Current change to valpred */ int index; /* Current step change index */ int outputbuffer; /* place to keep previous 4-bit value */ int bufferstep; /* toggle between outputbuffer/output */ outp = (signed char *)outdata; inp = indata; valpred = state->valprev; index = state->index; step = stepsizeTable[index]; bufferstep = 1; for ( ; len > 0 ; len-- ) { val = *inp++; /* Step 1 - compute difference with previous value */ diff = val - valpred; sign = (diff < 0) ? 8 : 0; if(sign) diff = (-diff); /* Step 2 - Divide and clamp ** This code *approximately* computes: ** delta = diff*4/step; ** vpdiff = (delta+0.5)*step/4; ** but in shift step bits are dropped. The net result of this is ** that even if you have fast mul/div hardware you cannot put it to ** good use since the fixup would be too expensive. */ delta = 0; vpdiff = (step >> 3); if(diff >= step) { delta = 4; diff -= step; vpdiff += step; } step >>= 1; if(diff >= step) { delta ¦= 2; diff -= step; vpdiff += step; } step >>= 1; if(diff >= step) { delta ¦= 1; vpdiff += step; } /* Step 3 - Update previous value */ if( sign ) valpred -= vpdiff; else valpred += vpdiff; /* Step 4 - Clamp previous value to 16 bits */ if( valpred > 32767 ) valpred = 32767; else if(valpred < -32768) valpred = -32768; /* Step 5 - Assemble value, update index and step values */ delta ¦= sign; index += indexTable[delta]; if(index < 0) index = 0; if(index > 88) index = 88; step = stepsizeTable[index]; /* Step 6 - Output value */ if(bufferstep) { outputbuffer = (delta << 4) & 0xf0; } else { *outp++ = (delta & 0x0f) ¦ outputbuffer; } bufferstep = !bufferstep; } /* Output last step, if needed */ if(!bufferstep) *outp++ = outputbuffer; state->valprev = valpred; state->index = index;}void G721::adpcm_decoder(char* indata,short* outdata,int len,adpcm_state* state){ signed char *inp; /* Input buffer pointer */ short *outp; /* output buffer pointer */ int sign; /* Current adpcm sign bit */ int delta; /* Current adpcm output value */ int step; /* Stepsize */ int valpred; /* Predicted value */ int vpdiff; /* Current change to valpred */ int index; /* Current step change index */ int inputbuffer; /* place to keep next 4-bit value */ int bufferstep; /* toggle between inputbuffer/input */ outp = outdata; inp = (signed char *)indata; valpred = state->valprev; index = state->index; step = stepsizeTable[index]; bufferstep = 0; for( ; len > 0 ; len--) { /* Step 1 - get the delta value */ if(bufferstep) { delta = inputbuffer & 0xf; } else { inputbuffer = *inp++; delta = (inputbuffer >> 4) & 0xf; } bufferstep = !bufferstep; /* Step 2 - Find new index value (for later) */ index += indexTable[delta]; if(index < 0 ) index = 0; if(index > 88) index = 88; /* Step 3 - Separate sign and magnitude */ sign = delta & 8; delta = delta & 7; /* Step 4 - Compute difference and new predicted value */ /* ** Computes 'vpdiff = (delta+0.5)*step/4', but see comment ** in adpcm_coder. */ vpdiff = step >> 3; if(delta & 4) vpdiff += step; if(delta & 2) vpdiff += step>>1; if(delta & 1) vpdiff += step>>2; if(sign) valpred -= vpdiff; else valpred += vpdiff; /* Step 5 - clamp output value */ if(valpred > 32767) valpred = 32767; else if ( valpred < -32768 ) valpred = -32768; /* Step 6 - Update step value */ step = stepsizeTable[index]; /* Step 7 - Output value */ *outp++ = valpred; } state->valprev = valpred; state->index = index;} 有问题向各位高手求教!!!谢谢!!! 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{
short valprev; /* Previous output value */
char index; /* Index into stepsize table */
};class G721 // ADPCM codec
{
public:
G721();
~G721();
void adpcm_coder(short* indata,char* outdata,int len,
adpcm_state* state);
void adpcm_decoder(char* indata,short* outdata,int len,
adpcm_state* state);
};// adpcm.cpp
#include "stdafx.h"
#include "adpcm.h"
//#include "stdio.h" static int indexTable[16] =
{
-1, -1, -1, -1, 2, 4, 6, 8,
-1, -1, -1, -1, 2, 4, 6, 8,
};static int stepsizeTable[89] =
{
7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
50, 55, 60, 66, 73, 80, 88, 97,107,118,
130,143,157,173,190,209,230,253,279,307,
337,371,408,449,494,544,598,658,724,796,
876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
5894, 6484, 7132, 7845, 8630, 9493,10442,11487,12635,13899,
15289,16818,18500,20350,22385,24623,27086,29794,32767
};G721::~G721()
{
}G721::G721()
{}
void G721::adpcm_coder(short* indata,char* outdata,int len,adpcm_state* state)
{
short *inp; /* Input buffer pointer */
signed char *outp; /* output buffer pointer */
int val; /* Current input sample value */
int sign; /* Current adpcm sign bit */
int delta; /* Current adpcm output value */
int diff; /* Difference between val and valprev */
int step; /* Stepsize */
int valpred; /* Predicted output value */
int vpdiff; /* Current change to valpred */
int index; /* Current step change index */
int outputbuffer; /* place to keep previous 4-bit value */
int bufferstep; /* toggle between outputbuffer/output */ outp = (signed char *)outdata;
inp = indata;
valpred = state->valprev;
index = state->index;
step = stepsizeTable[index];
bufferstep = 1; for ( ; len > 0 ; len-- )
{
val = *inp++; /* Step 1 - compute difference with previous value */
diff = val - valpred;
sign = (diff < 0) ? 8 : 0;
if(sign) diff = (-diff); /* Step 2 - Divide and clamp
** This code *approximately* computes:
** delta = diff*4/step;
** vpdiff = (delta+0.5)*step/4;
** but in shift step bits are dropped. The net result of this is
** that even if you have fast mul/div hardware you cannot put it to
** good use since the fixup would be too expensive.
*/
delta = 0;
vpdiff = (step >> 3);
if(diff >= step)
{
delta = 4;
diff -= step;
vpdiff += step;
}
step >>= 1;
if(diff >= step)
{
delta ¦= 2;
diff -= step;
vpdiff += step;
}
step >>= 1;
if(diff >= step)
{
delta ¦= 1;
vpdiff += step;
}
/* Step 3 - Update previous value */
if( sign )
valpred -= vpdiff;
else
valpred += vpdiff;
/* Step 4 - Clamp previous value to 16 bits */
if( valpred > 32767 )
valpred = 32767;
else if(valpred < -32768)
valpred = -32768;
/* Step 5 - Assemble value, update index and step values */
delta ¦= sign;
index += indexTable[delta];
if(index < 0) index = 0;
if(index > 88) index = 88;
step = stepsizeTable[index];
/* Step 6 - Output value */
if(bufferstep)
{
outputbuffer = (delta << 4) & 0xf0;
}
else
{
*outp++ = (delta & 0x0f) ¦ outputbuffer;
}
bufferstep = !bufferstep;
}
/* Output last step, if needed */
if(!bufferstep)
*outp++ = outputbuffer;
state->valprev = valpred;
state->index = index;
}void G721::adpcm_decoder(char* indata,short* outdata,int len,adpcm_state* state)
{
signed char *inp; /* Input buffer pointer */
short *outp; /* output buffer pointer */
int sign; /* Current adpcm sign bit */
int delta; /* Current adpcm output value */
int step; /* Stepsize */
int valpred; /* Predicted value */
int vpdiff; /* Current change to valpred */
int index; /* Current step change index */
int inputbuffer; /* place to keep next 4-bit value */
int bufferstep; /* toggle between inputbuffer/input */ outp = outdata;
inp = (signed char *)indata;
valpred = state->valprev;
index = state->index;
step = stepsizeTable[index];
bufferstep = 0;
for( ; len > 0 ; len--)
{
/* Step 1 - get the delta value */
if(bufferstep)
{
delta = inputbuffer & 0xf;
}
else
{
inputbuffer = *inp++;
delta = (inputbuffer >> 4) & 0xf;
}
bufferstep = !bufferstep;
/* Step 2 - Find new index value (for later) */
index += indexTable[delta];
if(index < 0 ) index = 0;
if(index > 88) index = 88;
/* Step 3 - Separate sign and magnitude */
sign = delta & 8;
delta = delta & 7;
/* Step 4 - Compute difference and new predicted value */
/*
** Computes 'vpdiff = (delta+0.5)*step/4', but see comment
** in adpcm_coder.
*/
vpdiff = step >> 3;
if(delta & 4) vpdiff += step;
if(delta & 2) vpdiff += step>>1;
if(delta & 1) vpdiff += step>>2;
if(sign)
valpred -= vpdiff;
else
valpred += vpdiff;
/* Step 5 - clamp output value */
if(valpred > 32767)
valpred = 32767;
else if ( valpred < -32768 )
valpred = -32768;
/* Step 6 - Update step value */
step = stepsizeTable[index];
/* Step 7 - Output value */
*outp++ = valpred;
}
state->valprev = valpred;
state->index = index;
}