ima_adpcm_state_t decode_ima_adpcm_u8_i16(unsigned char* input, short* output, int input_length, ima_adpcm_state_t state)
{
int k=0;
for(int i=0;i<input_length;i++)
{
output[k++]=ImaAdpcmDecode(input[i]&0xf,&state);
output[k++]=ImaAdpcmDecode( (input[i]>>4)&0xf,&state);
}
return state;
}
void decode_ima_adpcm_e8_i16(unsigned char* input, short* output, int input_length, ima_adpcm_state_t *state)
{
state->pos_clamp = +32767;
state->neg_clamp = -32768;
int i, k=0;
for (i=0; i<input_length; i++)
{
output[k++] = ImaAdpcmDecode(input[i]&0xf, state);
output[k++] = ImaAdpcmDecode((input[i]>>4)&0xf, state);
}
}
void decode_ima_adpcm_e8_u8(unsigned char* input, unsigned char* output, int input_length, ima_adpcm_state_t *state)
{
// not +127 / -128 because unsigned
state->pos_clamp = 255;
state->neg_clamp = 0;
int i, k=0;
for (i=0; i<input_length; i++)
{
output[k++] = ImaAdpcmDecode(input[i]&0xf, state);
output[k++] = ImaAdpcmDecode((input[i]>>4)&0xf, state);
}
}
static inline unsigned char ImaAdpcmEncode(short sample, ima_adpcm_state_t* state) {
int diff = sample - state->previousValue;
int step = _stepSizeTable[state->index];
int deltaCode = 0;
// Set sign bit
if (diff < 0) { deltaCode = 8; diff = -diff; }
// This is essentially deltaCode = (diff<<2)/step,
// except the roundoff is handled differently.
if ( diff >= step ) { deltaCode |= 4; diff -= step; }
step >>= 1;
if ( diff >= step ) { deltaCode |= 2; diff -= step; }
step >>= 1;
if ( diff >= step ) { deltaCode |= 1; diff -= step; }
ImaAdpcmDecode(deltaCode,state); // update state
return deltaCode;
}
