int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
                                int start, int end, int fast_gain, int is_lfe,
                                int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
                                uint8_t *dba_lengths, uint8_t *dba_values,
                                int16_t *mask)
{
    int16_t excite[50]; /* excitation */
    int bin, k;
    int bndstrt, bndend, begin, end1, tmp;
    int lowcomp, fastleak, slowleak;

    /* excitation function */
    bndstrt = bin_to_band_tab[start];
    bndend = bin_to_band_tab[end-1] + 1;

    if (bndstrt == 0) {
        lowcomp = 0;
        lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
        excite[0] = band_psd[0] - fast_gain - lowcomp;
        lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
        excite[1] = band_psd[1] - fast_gain - lowcomp;
        begin = 7;
        for (bin = 2; bin < 7; bin++) {
            if (!(is_lfe && bin == 6))
                lowcomp = calc_lowcomp1(lowcomp, band_psd[bin], band_psd[bin+1], 384);
            fastleak = band_psd[bin] - fast_gain;
            slowleak = band_psd[bin] - s->slow_gain;
            excite[bin] = fastleak - lowcomp;
            if (!(is_lfe && bin == 6)) {
                if (band_psd[bin] <= band_psd[bin+1]) {
                    begin = bin + 1;
                    break;
                }
            }
        }

        end1=bndend;
        if (end1 > 22) end1=22;

        for (bin = begin; bin < end1; bin++) {
            if (!(is_lfe && bin == 6))
                lowcomp = calc_lowcomp(lowcomp, band_psd[bin], band_psd[bin+1], bin);

            fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
            slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
            excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
        }
        begin = 22;
    } else {
        /* coupling channel */
        begin = bndstrt;

        fastleak = (s->cpl_fast_leak << 8) + 768;
        slowleak = (s->cpl_slow_leak << 8) + 768;
    }

    for (bin = begin; bin < bndend; bin++) {
        fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
        slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
        excite[bin] = FFMAX(fastleak, slowleak);
    }

    /* compute masking curve */

    for (bin = bndstrt; bin < bndend; bin++) {
        tmp = s->db_per_bit - band_psd[bin];
        if (tmp > 0) {
            excite[bin] += tmp >> 2;
        }
        mask[bin] = FFMAX(ff_ac3_hearing_threshold_tab[bin >> s->sr_shift][s->sr_code], excite[bin]);
    }

    /* delta bit allocation */

    if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
        int band, seg, delta;
        if (dba_nsegs >= 8)
            return -1;
        band = 0;
        for (seg = 0; seg < dba_nsegs; seg++) {
            band += dba_offsets[seg];
            if (band >= 50 || dba_lengths[seg] > 50-band)
                return -1;
            if (dba_values[seg] >= 4) {
                delta = (dba_values[seg] - 3) << 7;
            } else {
                delta = (dba_values[seg] - 4) << 7;
            }
            for (k = 0; k < dba_lengths[seg]; k++) {
                mask[band] += delta;
                band++;
            }
        }
    }
    return 0;
}