static int jpeg2000_decode_packets(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile)
{
    int layno, reslevelno, compno, precno, ok_reslevel;
    int x, y;

    s->bit_index = 8;
    switch (tile->codsty[0].prog_order) {
    case JPEG2000_PGOD_LRCP:
    case JPEG2000_PGOD_RLCP:
        for (layno = 0; layno < tile->codsty[0].nlayers; layno++) {
            ok_reslevel = 1;
            for (reslevelno = 0; ok_reslevel; reslevelno++) {
                ok_reslevel = 0;
                for (compno = 0; compno < s->ncomponents; compno++) {
                    Jpeg2000CodingStyle *codsty = tile->codsty + compno;
                    Jpeg2000QuantStyle *qntsty  = tile->qntsty + compno;
                    if (reslevelno < codsty->nreslevels) {
                        Jpeg2000ResLevel *rlevel = tile->comp[compno].reslevel +
                                                reslevelno;
                        ok_reslevel = 1;
                        for (precno = 0; precno < rlevel->num_precincts_x * rlevel->num_precincts_y; precno++)
                            if (jpeg2000_decode_packet(s,
                                                       codsty, rlevel,
                                                       precno, layno,
                                                       qntsty->expn + (reslevelno ? 3 * (reslevelno - 1) + 1 : 0),
                                                       qntsty->nguardbits))
                                return -1;
                    }
                }
            }
        }
        break;

    case JPEG2000_PGOD_CPRL:
        for (compno = 0; compno < s->ncomponents; compno++) {
            Jpeg2000CodingStyle *codsty = tile->codsty + compno;
            Jpeg2000QuantStyle *qntsty  = tile->qntsty + compno;

            /* Set bit stream buffer address according to tile-part.
             * For DCinema one tile-part per component, so can be
             * indexed by component. */
            s->g = tile->tile_part[compno].tpg;

            /* Position loop (y axis)
             * TODO: Automate computing of step 256.
             * Fixed here, but to be computed before entering here. */
            for (y = 0; y < s->height; y += 256) {
                /* Position loop (y axis)
                 * TODO: automate computing of step 256.
                 * Fixed here, but to be computed before entering here. */
                for (x = 0; x < s->width; x += 256) {
                    for (reslevelno = 0; reslevelno < codsty->nreslevels; reslevelno++) {
                        uint16_t prcx, prcy;
                        uint8_t reducedresno = codsty->nreslevels - 1 -reslevelno; //  ==> N_L - r
                        Jpeg2000ResLevel *rlevel = tile->comp[compno].reslevel + reslevelno;

                        if (!((y % (1 << (rlevel->log2_prec_height + reducedresno)) == 0) ||
                              (y == 0))) // TODO: 2nd condition simplified as try0 always =0 for dcinema
                            continue;

                        if (!((x % (1 << (rlevel->log2_prec_width + reducedresno)) == 0) ||
                              (x == 0))) // TODO: 2nd condition simplified as try0 always =0 for dcinema
                            continue;

                        // check if a precinct exists
                        prcx   = ff_jpeg2000_ceildivpow2(x, reducedresno) >> rlevel->log2_prec_width;
                        prcy   = ff_jpeg2000_ceildivpow2(y, reducedresno) >> rlevel->log2_prec_height;
                        precno = prcx + rlevel->num_precincts_x * prcy;
                        for (layno = 0; layno < tile->codsty[0].nlayers; layno++) {
                            if (jpeg2000_decode_packet(s, codsty, rlevel,
                                                       precno, layno,
                                                       qntsty->expn + (reslevelno ? 3 * (reslevelno - 1) + 1 : 0),
                                                       qntsty->nguardbits))
                                return -1;
                        }
                    }
                }
            }
        }
        break;

    default:
        break;
    }

    /* EOC marker reached */
    bytestream2_skip(&s->g, 2);

    return 0;
}