syntax.c

the mpeg2/4 aac decoder

            ics->sect_end[g][i] = k + sect_len;

#if 0
            printf("%d\n", ics->sect_start[g][i]);
#endif
#if 0
            printf("%d\n", ics->sect_end[g][i]);
#endif

            if (k + sect_len >= 8*15)
                return 15;
            if (i >= 8*15)
                return 15;

            for (sfb = k; sfb < k + sect_len; sfb++)
            {
                ics->sfb_cb[g][sfb] = ics->sect_cb[g][i];
#if 0
                printf("%d\n", ics->sfb_cb[g][sfb]);
#endif
            }

#if 0
            printf(" %6d %6d %6d\n",
                i,
                ics->sect_end[g][i],
                ics->sect_cb[g][i]);
#endif

            k += sect_len;
            i++;
        }
        ics->num_sec[g] = i;
#if 0
        printf("%d\n", ics->num_sec[g]);
#endif
    }

#if 0
    printf("\n");
#endif

    return 0;
}

/*
 *  decode_scale_factors()
 *   decodes the scalefactors from the bitstream
 */
/*
 * All scalefactors (and also the stereo positions and pns energies) are
 * transmitted using Huffman coded DPCM relative to the previous active
 * scalefactor (respectively previous stereo position or previous pns energy,
 * see subclause 4.6.2 and 4.6.3). The first active scalefactor is
 * differentially coded relative to the global gain.
 */
static uint8_t decode_scale_factors(ic_stream *ics, bitfile *ld)
{
    uint8_t g, sfb;
    int16_t t;
    int8_t noise_pcm_flag = 1;

    int16_t scale_factor = ics->global_gain;
    int16_t is_position = 0;
    int16_t noise_energy = ics->global_gain - 90;

    for (g = 0; g < ics->num_window_groups; g++)
    {
        for (sfb = 0; sfb < ics->max_sfb; sfb++)
        {
            switch (ics->sfb_cb[g][sfb])
            {
            case ZERO_HCB: /* zero book */
                ics->scale_factors[g][sfb] = 0;
//#define SF_PRINT
#ifdef SF_PRINT
                printf("%d\n", ics->scale_factors[g][sfb]);
#endif
                break;
            case INTENSITY_HCB: /* intensity books */
            case INTENSITY_HCB2:

                /* decode intensity position */
                t = huffman_scale_factor(ld);
                is_position += (t - 60);
                ics->scale_factors[g][sfb] = is_position;
#ifdef SF_PRINT
                printf("%d\n", ics->scale_factors[g][sfb]);
#endif

                break;
            case NOISE_HCB: /* noise books */

                /* decode noise energy */
                if (noise_pcm_flag)
                {
                    noise_pcm_flag = 0;
                    t = (int16_t)faad_getbits(ld, 9
                        DEBUGVAR(1,73,"scale_factor_data(): first noise")) - 256;
                } else {
                    t = huffman_scale_factor(ld);
                    t -= 60;
                }
                noise_energy += t;
                ics->scale_factors[g][sfb] = noise_energy;
#ifdef SF_PRINT
                printf("%d\n", ics->scale_factors[g][sfb]);
#endif

                break;
            default: /* spectral books */

                /* ics->scale_factors[g][sfb] must be between 0 and 255 */

                ics->scale_factors[g][sfb] = 0;

                /* decode scale factor */
                t = huffman_scale_factor(ld);
                scale_factor += (t - 60);
                if (scale_factor < 0 || scale_factor > 255)
                    return 4;
                ics->scale_factors[g][sfb] = scale_factor;
#ifdef SF_PRINT
                printf("%d\n", ics->scale_factors[g][sfb]);
#endif

                break;
            }
        }
    }

    return 0;
}

/* Table 4.4.26 */
static uint8_t scale_factor_data(NeAACDecHandle hDecoder, ic_stream *ics, bitfile *ld)
{
    uint8_t ret = 0;
#ifdef PROFILE
    int64_t count = faad_get_ts();
#endif

#ifdef ERROR_RESILIENCE
    if (!hDecoder->aacScalefactorDataResilienceFlag)
    {
#endif
        ret = decode_scale_factors(ics, ld);
#ifdef ERROR_RESILIENCE
    } else {
        /* In ER AAC the parameters for RVLC are seperated from the actual
           data that holds the scale_factors.
           Strangely enough, 2 parameters for HCR are put inbetween them.
        */
        ret = rvlc_scale_factor_data(ics, ld);
    }
#endif

#ifdef PROFILE
    count = faad_get_ts() - count;
    hDecoder->scalefac_cycles += count;
#endif

    return ret;
}

/* Table 4.4.27 */
static void tns_data(ic_stream *ics, tns_info *tns, bitfile *ld)
{
    uint8_t w, filt, i, start_coef_bits, coef_bits;
    uint8_t n_filt_bits = 2;
    uint8_t length_bits = 6;
    uint8_t order_bits = 5;

    if (ics->window_sequence == EIGHT_SHORT_SEQUENCE)
    {
        n_filt_bits = 1;
        length_bits = 4;
        order_bits = 3;
    }

    for (w = 0; w < ics->num_windows; w++)
    {
        tns->n_filt[w] = (uint8_t)faad_getbits(ld, n_filt_bits
            DEBUGVAR(1,74,"tns_data(): n_filt"));
#if 0
        printf("%d\n", tns->n_filt[w]);
#endif

        if (tns->n_filt[w])
        {
            if ((tns->coef_res[w] = faad_get1bit(ld
                DEBUGVAR(1,75,"tns_data(): coef_res"))) & 1)
            {
                start_coef_bits = 4;
            } else {
                start_coef_bits = 3;
            }
#if 0
            printf("%d\n", tns->coef_res[w]);
#endif
        }

        for (filt = 0; filt < tns->n_filt[w]; filt++)
        {
            tns->length[w][filt] = (uint8_t)faad_getbits(ld, length_bits
                DEBUGVAR(1,76,"tns_data(): length"));
#if 0
            printf("%d\n", tns->length[w][filt]);
#endif
            tns->order[w][filt]  = (uint8_t)faad_getbits(ld, order_bits
                DEBUGVAR(1,77,"tns_data(): order"));
#if 0
            printf("%d\n", tns->order[w][filt]);
#endif
            if (tns->order[w][filt])
            {
                tns->direction[w][filt] = faad_get1bit(ld
                    DEBUGVAR(1,78,"tns_data(): direction"));
#if 0
                printf("%d\n", tns->direction[w][filt]);
#endif
                tns->coef_compress[w][filt] = faad_get1bit(ld
                    DEBUGVAR(1,79,"tns_data(): coef_compress"));
#if 0
                printf("%d\n", tns->coef_compress[w][filt]);
#endif

                coef_bits = start_coef_bits - tns->coef_compress[w][filt];
                for (i = 0; i < tns->order[w][filt]; i++)
                {
                    tns->coef[w][filt][i] = (uint8_t)faad_getbits(ld, coef_bits
                        DEBUGVAR(1,80,"tns_data(): coef"));
#if 0
                    printf("%d\n", tns->coef[w][filt][i]);
#endif
                }
            }
        }
    }
}

#ifdef LTP_DEC
/* Table 4.4.28 */
static uint8_t ltp_data(NeAACDecHandle hDecoder, ic_stream *ics, ltp_info *ltp, bitfile *ld)
{
    uint8_t sfb, w;

    ltp->lag = 0;

#ifdef LD_DEC
    if (hDecoder->object_type == LD)
    {
        ltp->lag_update = (uint8_t)faad_getbits(ld, 1
            DEBUGVAR(1,142,"ltp_data(): lag_update"));

        if (ltp->lag_update)
        {
            ltp->lag = (uint16_t)faad_getbits(ld, 10
                DEBUGVAR(1,81,"ltp_data(): lag"));
        }
    } else {
#endif
        ltp->lag = (uint16_t)faad_getbits(ld, 11
            DEBUGVAR(1,81,"ltp_data(): lag"));
#ifdef LD_DEC
    }
#endif

    /* Check length of lag */
    if (ltp->lag > (hDecoder->frameLength << 1))
        return 18;

    ltp->coef = (uint8_t)faad_getbits(ld, 3
        DEBUGVAR(1,82,"ltp_data(): coef"));

    if (ics->window_sequence == EIGHT_SHORT_SEQUENCE)
    {
        for (w = 0; w < ics->num_windows; w++)
        {
            if ((ltp->short_used[w] = faad_get1bit(ld
                DEBUGVAR(1,83,"ltp_data(): short_used"))) & 1)
            {
                ltp->short_lag_present[w] = faad_get1bit(ld
                    DEBUGVAR(1,84,"ltp_data(): short_lag_present"));
                if (ltp->short_lag_present[w])
                {
                    ltp->short_lag[w] = (uint8_t)faad_getbits(ld, 4
                        DEBUGVAR(1,85,"ltp_data(): short_lag"));
                }
            }
        }
    } else {
        ltp->last_band = (ics->max_sfb < MAX_LTP_SFB ? ics->max_sfb : MAX_LTP_SFB);

        for (sfb = 0; sfb < ltp->last_band; sfb++)
        {
            ltp->long_used[sfb] = faad_get1bit(ld
                DEBUGVAR(1,86,"ltp_data(): long_used"));
        }
    }

    return 0;
}
#endif

/* Table 4.4.29 */
static uint8_t spectral_data(NeAACDecHandle hDecoder, ic_stream *ics, bitfile *ld,
                             int16_t *spectral_data)
{
    int8_t i;
    uint8_t g;
    uint16_t inc, k, p = 0;
    uint8_t groups = 0;
    uint8_t sect_cb;
    uint8_t result;
    uint16_t nshort = hDecoder->frameLength/8;

#ifdef PROFILE
    int64_t count = faad_get_ts();
#endif

    for(g = 0; g < ics->num_window_groups; g++)
    {
        p = groups*nshort;

        for (i = 0; i < ics->num_sec[g]; i++)
        {
            sect_cb = ics->sect_cb[g][i];

            inc = (sect_cb >= FIRST_PAIR_HCB) ? 2 : 4;

            switch (sect_cb)
            {
            case ZERO_HCB:
            case NOISE_HCB:
            case INTENSITY_HCB:
            case INTENSITY_HCB2:
//#define SD_PRINT
#ifdef SD_PRINT
                {
                    int j;
                    for (j = ics->sect_sfb_offset[g][ics->sect_start[g][i]]; j < ics->sect_sfb_offset[g][ics->sect_end[g][i]]; j++)
                    {
                        printf("%d\n", 0);
                    }
                }
#endif
//#define SFBO_PRINT
#ifdef SFBO_PRINT
                printf("%d\n", ics->sect_sfb_offset[g][ics->sect_start[g][i]]);
#endif
                p += (ics->sect_sfb_offset[g][ics->sect_end[g][i]] -
                    ics->sect_sfb_offset[g][ics->sect_start[g][i]]);
                break;
            default:
#ifdef SFBO_PRINT
                printf("%d\n", ics->sect_sfb_offset[g][ics->sect_start[g][i]]);
#endif
                for (k = ics->sect_sfb_offset[g][ics->sect_start[g][i]];
                     k < ics->sect_sfb_offset[g][ics->sect_end[g][i]]; k += inc)
                {
                    if ((result = huffman_spectral_data(sect_cb, ld, &spectral_data[p])) > 0)
                        return result;
#ifdef SD_PRINT
                    {
                        int j;
                        for (j = p; j < p+inc; j++)
                        {
                            printf("%d\n", spectral_data[j]);
                        }
                    }
#endif
                    p += inc;
                }
                break;
            }
        }
        groups += ics->window_group_length[g];
    }

#ifdef PROFILE
    count = faad_get_ts() - count;
    hDecoder->spectral_cycles += count;
#endif

    return 0;
}

/* Table 4.4.30 */
static uint16_t extension_payload(bitfile *ld, drc_info *drc, uint16_t count)
{
    uint16_t i, n, dataElementLength;
    uint8_t dataElementLengthPart;
    uint8_t align = 4, data_element_version, loopCounter;

    uint8_t extension_type = (uint8_t)faad_getbits(ld, 4
        DEBUGVAR(1,87,"extension_payload(): extension_type"));

    switch (extension_type)
    {
    case EXT_DYNAMIC_RANGE:
        drc->present = 1;
        n = dynamic_range_info(ld, drc);
        return n;
    case EXT_FILL_DATA:
        /* fill_nibble = */ faad_getbits(ld, 4
            DEBUGVAR(1,136,"extension_payload(): fill_nibble")); /* must be