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
}

小广告:

FFmpeg音视频高级开发实战5 iOS/Android/windows/Linux

http://edu.csdn.net/course/detail/2314