ref: 4554e1f0311a0d0f9b62ea8b013fffcfcd82fa7f
dir: /src/adpcms.h/
typedef struct adpcm_struct
{
int last_output;
int step_index;
int max_step_index;
int const * steps;
int mask;
} * adpcm_t;
int adpcm_decode(int code, adpcm_t state); /* 4-bit -> 16-bit */
int adpcm_encode(int sample, adpcm_t state); /* 16-bit -> 4-bit */
void adpcm_init(adpcm_t state, int type /* 0:IMA, 1:OKI */);