ADPCM音频格式 编解码

#ifdef __cplusplus

extern "C" {

#endif /* __cplusplus */

    

    void ResetADPCMEncoder();

    void ResetADPCMDecoder();

    void EncodeADPCM(unsignedchar *pRaw, int nLenRaw,unsigned char *pBufEncoded);

    void DecodeADPCM(char *in,int inLen, char *out,int outLen);

    

    

#ifdef __cplusplus

}

#endif /* __cplusplus */

#ifdef __cplus

#include <iostream>

#endif

#include "adpcm.h"

int g_nEnAudioPreSample=0;

int g_nEnAudioIndex=0;

int g_nDeAudioPreSample=0;

int g_nDeAudioIndex=0;

static int gs_index_adjust[16]=//{-1,-1,-1,-1,2,4,6,8};

{-1, -1, -1, -1, 2,

    4, 6,  8, -1, -1,

    -1, -1, 2,  4, 6,

    8 };

static int gs_step_table[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

};

void ResetADPCMEncoder()

{

    g_nEnAudioPreSample=0;

    g_nEnAudioIndex=0;

}

void EncodeADPCM(unsignedchar *pRaw, int nLenRaw,unsigned char *pBufEncoded)

{

short *pcm = (short *)pRaw;

int cur_sample;

int i;

int delta;

int sb;

int code;

nLenRaw >>= 1;

    

for(i =0; i<nLenRaw; i++)

{

cur_sample = pcm[i];

delta = cur_sample - g_nEnAudioPreSample;

if (delta <0){

delta = -delta;

sb = 8;

}else sb =0;

        

code = 4 * delta /gs_step_table[g_nEnAudioIndex];

if (code>7)code=7;

        

delta = (gs_step_table[g_nEnAudioIndex] * code) /4 + gs_step_table[g_nEnAudioIndex] /8;

if(sb) delta = -delta;

        

g_nEnAudioPreSample += delta;

if (g_nEnAudioPreSample >32767) g_nEnAudioPreSample =32767;

elseif (g_nEnAudioPreSample < -32768)g_nEnAudioPreSample = -32768;

        

g_nEnAudioIndex +=gs_index_adjust[code];

if(g_nEnAudioIndex <0) g_nEnAudioIndex =0;

elseif(g_nEnAudioIndex >88) g_nEnAudioIndex =88;

        

if(i &0x01) pBufEncoded[i>>1] |= code | sb;

else pBufEncoded[i>>1] = (code | sb) <<4;

}

}

void ResetADPCMDecoder()

{

    g_nDeAudioPreSample=0;

    g_nDeAudioIndex=0;

}

void DecodeADPCM(char *in,int inLen, char *out,int outLen)

{

char* pDataCompressed = in;

int i;

int code;

int sb;

int delta;

unsignedshort *pcm = (unsignedshort *)out;

int nLenData = outLen >>1;

for(i=0; i<nLenData; i++)

{

if(i &0x01) code = pDataCompressed[i>>1] &0x0f;

else code = pDataCompressed[i>>1] >>4;

if((code &8) != 0) sb =1;

else sb =0;

code &= 7;

delta = (gs_step_table[g_nDeAudioIndex] * code) /4 + gs_step_table[g_nDeAudioIndex] /8;

if(sb) delta = -delta;

g_nDeAudioPreSample += delta;

if(g_nDeAudioPreSample >32767) g_nDeAudioPreSample =32767;

elseif (g_nDeAudioPreSample < -32768)g_nDeAudioPreSample = -32768;

pcm[i] = g_nDeAudioPreSample;

g_nDeAudioIndex+=gs_index_adjust[code];

if(g_nDeAudioIndex <0) g_nDeAudioIndex =0;

if(g_nDeAudioIndex >88) g_nDeAudioIndex=88;

}

#if 0

LOG(@"With problem at UID:DZJTATRP98U7AMPPWFWS");

int valpred =0;

int index =0;

    // int volset = 100;

int step;

int vpdiff;

unsignedchar buffer_step = 0;

step = gs_step_table[index];

unsignedchar* R_TargetBuffer = (unsignedchar*)out;

int Source_Idx =4;

int Target_Idx =0;

inLen -= 4;

for (inLen <<=1; inLen > 0; inLen--) {

unsignedchar delta = (unsignedchar)in[Source_Idx];

if (buffer_step ==0) {

delta >>= 4;

} else {

Source_Idx++;// set to next byte

}

delta &= 0x0f;

buffer_step ^= 1;

/* Step 2 - Find new index value (for later) */

index += gs_index_adjust[delta];

if (index <0) {

index = 0;

} elseif (index > 88) {

index = 88;

}

vpdiff = step >> 3;

if ((delta &4) != 0)

vpdiff += step;

if ((delta &2) != 0)

vpdiff += step >>1;

if ((delta &1) != 0)

vpdiff += step >>2;

// if (sign != 0)

if (delta >7) {

valpred -= vpdiff;

} else {

valpred += vpdiff;

}

/* Step 5 - clamp output value */

if (valpred >32767) {

valpred = 32767;

} elseif (valpred < -32768) {

valpred = -32768;

}

/* Step 6 - Update step value */

step = gs_step_table[index];

/* Step 7 - Output value */

if (Target_Idx +2 > outLen)

break;

        // if (volset != 100)

        // valpred = valpred * volset / 100;

int tmp = (short) valpred;

R_TargetBuffer[Target_Idx++] = (unsignedchar)(tmp & 0x0FF);

tmp >>= 8;

R_TargetBuffer[Target_Idx++] = (unsignedchar)(tmp & 0x0FF);

}

    // return Target_Idx;

#endif

}

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