static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
                                                    int16_t *block, int n)
{
    int level, i, j, run;
    RLTable *rl = &ff_rl_mpeg1;
    uint8_t * const scantable = s->intra_scantable.permutated;
    const int qscale          = s->qscale;
    OPEN_READER(re, &s->gb);
    i = -1;

    // special case for first coefficient, no need to add second VLC table
    UPDATE_CACHE(re, &s->gb);
    if (((int32_t)GET_CACHE(re, &s->gb)) < 0) {
        level = (3 * qscale) >> 1;
        if (GET_CACHE(re, &s->gb) & 0x40000000)
            level = -level;
        block[0] = level;
        i++;
        SKIP_BITS(re, &s->gb, 2);
        if (((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
            goto end;
    }

    /* now quantify & encode AC coefficients */
    for (;;) {
        GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);

        if (level != 0) {
            i += run;
            j  = scantable[i];
            level = ((level * 2 + 1) * qscale) >> 1;
            level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
            SKIP_BITS(re, &s->gb, 1);
        } else {
            /* escape */
            run = SHOW_UBITS(re, &s->gb, 6) + 1; LAST_SKIP_BITS(re, &s->gb, 6);
            UPDATE_CACHE(re, &s->gb);
            level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);

            i += run;
            j  = scantable[i];
            if (level < 0) {
                level = ((-level * 2 + 1) * qscale) >> 1;
                level = -level;
            } else {
                level = ((level * 2 + 1) * qscale) >> 1;
            }
        }

        block[j] = level;
        if (((int32_t)GET_CACHE(re, &s->gb)) <= (int32_t)0xBFFFFFFF)
            break;
        UPDATE_CACHE(re, &s->gb);
    }
end:
    LAST_SKIP_BITS(re, &s->gb, 2);
    CLOSE_READER(re, &s->gb);
    s->block_last_index[n] = i;
    return 0;
}