/**
 * Calculate the pitch vector by interpolating the past excitation at the pitch
 * pitch lag using a b60 hamming windowed sinc function
 *
 * @param p                   pointer to the AMRContext
 * @param lag_int             integer part of pitch lag
 * @param lag_frac            fractional part of pitch lag
 *
 * @return void
 */

static void interp_pitch_vector(AMRContext *p, int lag_int, int lag_frac) {
    int n, i;
    float *b60_idx1, *b60_idx2, *exc_idx;

    lag_frac *= -1;
    if(p->cur_frame_mode != MODE_122) {
        lag_frac <<= 1;
    }

    if(lag_frac < 0) {
        lag_frac += 6;
        lag_int--;
    }

    b60_idx1 = &b60[    lag_frac];
    b60_idx2 = &b60[6 - lag_frac];
    exc_idx = &p->prev_excitation[-lag_int];

    for(n=0; n<AMR_SUBFRAME_SIZE; n++) {
        for(i=0; i<10; i++) {
            p->pitch_vector[n] += b60_idx1[6*i] * exc_idx[-i];
        }
        exc_idx++;
        for(i=0; i<10; i++) {
            p->pitch_vector[n] += b60_idx2[6*i] * exc_idx[ i];
        }
        exc_idx++;
    }
}