sbr_hfadj.c

the mpeg2/4 aac decoder

            /* calculate the accumulated E_orig and E_curr over the limiter band */
            for (m = ml1; m < ml2; m++)
            {
                if ((m + sbr->kx) < sbr->f_table_res[sbr->f[ch][l]][current_res_band+1])
                {
                    current_res_band_size++;
                } else {
                    acc1 += pow2_int(-REAL_CONST(10) + log2_int_tab[current_res_band_size] + find_log2_E(sbr, current_res_band, l, ch));

                    current_res_band++;
                    current_res_band_size = 1;
                }

                acc2 += sbr->E_curr[ch][m][l];
            }
            acc1 += pow2_int(-REAL_CONST(10) + log2_int_tab[current_res_band_size] + find_log2_E(sbr, current_res_band, l, ch));


            if (acc1 == 0)
                acc1 = LOG2_MIN_INF;
            else
                acc1 = log2_int(acc1);


            /* calculate the maximum gain */
            /* ratio of the energy of the original signal and the energy
             * of the HF generated signal
             */
            G_max = acc1 - log2_int(acc2) + limGain[sbr->bs_limiter_gains];
            G_max = min(G_max, limGain[3]);


            for (m = ml1; m < ml2; m++)
            {
                real_t G;
                real_t E_curr, E_orig;
                real_t Q_orig, Q_orig_plus1;
                uint8_t S_index_mapped;


                /* check if m is on a noise band border */
                if ((m + sbr->kx) == sbr->f_table_noise[current_f_noise_band+1])
                {
                    /* step to next noise band */
                    current_f_noise_band++;
                }


                /* check if m is on a resolution band border */
                if ((m + sbr->kx) == sbr->f_table_res[sbr->f[ch][l]][current_res_band2+1])
                {
                    /* accumulate a whole range of equal Q_Ms */
                    if (Q_M_size > 0)
                        den += pow2_int(log2_int_tab[Q_M_size] + Q_M);
                    Q_M_size = 0;

                    /* step to next resolution band */
                    current_res_band2++;

                    /* if we move to a new resolution band, we should check if we are
                     * going to add a sinusoid in this band
                     */
                    S_mapped = get_S_mapped(sbr, ch, l, current_res_band2);
                }


                /* check if m is on a HI_RES band border */
                if ((m + sbr->kx) == sbr->f_table_res[HI_RES][current_hi_res_band+1])
                {
                    /* step to next HI_RES band */
                    current_hi_res_band++;
                }


                /* find S_index_mapped
                 * S_index_mapped can only be 1 for the m in the middle of the
                 * current HI_RES band
                 */
                S_index_mapped = 0;
                if ((l >= sbr->l_A[ch]) ||
                    (sbr->bs_add_harmonic_prev[ch][current_hi_res_band] && sbr->bs_add_harmonic_flag_prev[ch]))
                {
                    /* find the middle subband of the HI_RES frequency band */
                    if ((m + sbr->kx) == (sbr->f_table_res[HI_RES][current_hi_res_band+1] + sbr->f_table_res[HI_RES][current_hi_res_band]) >> 1)
                        S_index_mapped = sbr->bs_add_harmonic[ch][current_hi_res_band];
                }


                /* find bitstream parameters */
                if (sbr->E_curr[ch][m][l] == 0)
                    E_curr = LOG2_MIN_INF;
                else
                    E_curr = log2_int(sbr->E_curr[ch][m][l]);
                E_orig = -REAL_CONST(10) + find_log2_E(sbr, current_res_band2, l, ch);


                Q_orig = find_log2_Q(sbr, current_f_noise_band, current_t_noise_band, ch);
                Q_orig_plus1 = find_log2_Qplus1(sbr, current_f_noise_band, current_t_noise_band, ch);


                /* Q_M only depends on E_orig and Q_div2:
                 * since N_Q <= N_Low <= N_High we only need to recalculate Q_M on
                 * a change of current res band (HI or LO)
                 */
                Q_M = E_orig + Q_orig - Q_orig_plus1;


                /* S_M only depends on E_orig, Q_div and S_index_mapped:
                 * S_index_mapped can only be non-zero once per HI_RES band
                 */
                if (S_index_mapped == 0)
                {
                    S_M[m] = LOG2_MIN_INF; /* -inf */
                } else {
                    S_M[m] = E_orig - Q_orig_plus1;

                    /* accumulate sinusoid part of the total energy */
                    den += pow2_int(S_M[m]);
                }


                /* calculate gain */
                /* ratio of the energy of the original signal and the energy
                 * of the HF generated signal
                 */
                /* E_curr here is officially E_curr+1 so the log2() of that can never be < 0 */
                /* scaled by -10 */
                G = E_orig - max(-REAL_CONST(10), E_curr);
                if ((S_mapped == 0) && (delta == 1))
                {
                    /* G = G * 1/(1+Q) */
                    G -= Q_orig_plus1;
                } else if (S_mapped == 1) {
                    /* G = G * Q/(1+Q) */
                    G += Q_orig - Q_orig_plus1;
                }


                /* limit the additional noise energy level */
                /* and apply the limiter */
                if (G_max > G)
                {
                    Q_M_lim[m] = Q_M;
                    G_lim[m] = G;

                    if ((S_index_mapped == 0) && (l != sbr->l_A[ch]))
                    {
                        Q_M_size++;
                    }
                } else {
                    /* G > G_max */
                    Q_M_lim[m] = Q_M + G_max - G;
                    G_lim[m] = G_max;

                    /* accumulate limited Q_M */
                    if ((S_index_mapped == 0) && (l != sbr->l_A[ch]))
                    {
                        den += pow2_int(Q_M_lim[m]);
                    }
                }


                /* accumulate the total energy */
                /* E_curr changes for every m so we do need to accumulate every m */
                den += pow2_int(E_curr + G_lim[m]);
            }

            /* accumulate last range of equal Q_Ms */
            if (Q_M_size > 0)
            {
                den += pow2_int(log2_int_tab[Q_M_size] + Q_M);
            }


            /* calculate the final gain */
            /* G_boost: [0..2.51188643] */
            G_boost = acc1 - log2_int(den /*+ EPS*/);
            G_boost = min(G_boost, REAL_CONST(1.328771237) /* log2(1.584893192 ^ 2) */);


            for (m = ml1; m < ml2; m++)
            {
                /* apply compensation to gain, noise floor sf's and sinusoid levels */
#ifndef SBR_LOW_POWER
                adj->G_lim_boost[l][m] = pow2_fix((G_lim[m] + G_boost) >> 1);
#else
                /* sqrt() will be done after the aliasing reduction to save a
                 * few multiplies
                 */
                adj->G_lim_boost[l][m] = pow2_fix(G_lim[m] + G_boost);
#endif
                adj->Q_M_lim_boost[l][m] = pow2_fix((Q_M_lim[m] + G_boost) >> 1);

                if (S_M[m] != LOG2_MIN_INF)
                {
                    adj->S_M_boost[l][m] = pow2_int((S_M[m] + G_boost) >> 1);
                } else {
                    adj->S_M_boost[l][m] = 0;
                }
            }
        }
    }
}

#else

//#define LOG2_TEST

#ifdef LOG2_TEST

#define LOG2_MIN_INF -100000

__inline float pow2(float val)
{
    return pow(2.0, val);
}
__inline float log2(float val)
{
    return log(val)/log(2.0);
}

#define RB 14

float QUANTISE2REAL(float val)
{
    __int32 ival = (__int32)(val * (1<<RB));
    return (float)ival / (float)((1<<RB));
}

float QUANTISE2INT(float val)
{
    return floor(val);
}

/* log2 values of [0..63] */
static const real_t log2_int_tab[] = {