mpegaudiodec.c

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.10平台上编译为嵌入式图形界面操作系统。

}

#define ISQRT2 FIXR(0.70710678118654752440)

static void compute_stereo(MPADecodeContext *s,
                           GranuleDef *g0, GranuleDef *g1)
{
    int i, j, k, l;
    int32_t v1, v2;
    int sf_max, tmp0, tmp1, sf, len, non_zero_found;
    int32_t (*is_tab)[16];
    int32_t *tab0, *tab1;
    int non_zero_found_short[3];

    /* intensity stereo */
    if (s->mode_ext & MODE_EXT_I_STEREO) {
        if (!s->lsf) {
            is_tab = is_table;
            sf_max = 7;
        } else {
            is_tab = is_table_lsf[g1->scalefac_compress & 1];
            sf_max = 16;
        }
            
        tab0 = g0->sb_hybrid + 576;
        tab1 = g1->sb_hybrid + 576;

        non_zero_found_short[0] = 0;
        non_zero_found_short[1] = 0;
        non_zero_found_short[2] = 0;
        k = (13 - g1->short_start) * 3 + g1->long_end - 3;
        for(i = 12;i >= g1->short_start;i--) {
            /* for last band, use previous scale factor */
            if (i != 11)
                k -= 3;
            len = band_size_short[s->sample_rate_index][i];
            for(l=2;l>=0;l--) {
                tab0 -= len;
                tab1 -= len;
                if (!non_zero_found_short[l]) {
                    /* test if non zero band. if so, stop doing i-stereo */
                    for(j=0;j<len;j++) {
                        if (tab1[j] != 0) {
                            non_zero_found_short[l] = 1;
                            goto found1;
                        }
                    }
                    sf = g1->scale_factors[k + l];
                    if (sf >= sf_max)
                        goto found1;

                    v1 = is_tab[0][sf];
                    v2 = is_tab[1][sf];
                    for(j=0;j<len;j++) {
                        tmp0 = tab0[j];
                        tab0[j] = MULL(tmp0, v1);
                        tab1[j] = MULL(tmp0, v2);
                    }
                } else {
                found1:
                    if (s->mode_ext & MODE_EXT_MS_STEREO) {
                        /* lower part of the spectrum : do ms stereo
                           if enabled */
                        for(j=0;j<len;j++) {
                            tmp0 = tab0[j];
                            tmp1 = tab1[j];
                            tab0[j] = MULL(tmp0 + tmp1, ISQRT2);
                            tab1[j] = MULL(tmp0 - tmp1, ISQRT2);
                        }
                    }
                }
            }
        }

        non_zero_found = non_zero_found_short[0] | 
            non_zero_found_short[1] | 
            non_zero_found_short[2];

        for(i = g1->long_end - 1;i >= 0;i--) {
            len = band_size_long[s->sample_rate_index][i];
            tab0 -= len;
            tab1 -= len;
            /* test if non zero band. if so, stop doing i-stereo */
            if (!non_zero_found) {
                for(j=0;j<len;j++) {
                    if (tab1[j] != 0) {
                        non_zero_found = 1;
                        goto found2;
                    }
                }
                /* for last band, use previous scale factor */
                k = (i == 21) ? 20 : i;
                sf = g1->scale_factors[k];
                if (sf >= sf_max)
                    goto found2;
                v1 = is_tab[0][sf];
                v2 = is_tab[1][sf];
                for(j=0;j<len;j++) {
                    tmp0 = tab0[j];
                    tab0[j] = MULL(tmp0, v1);
                    tab1[j] = MULL(tmp0, v2);
                }
            } else {
            found2:
                if (s->mode_ext & MODE_EXT_MS_STEREO) {
                    /* lower part of the spectrum : do ms stereo
                       if enabled */
                    for(j=0;j<len;j++) {
                        tmp0 = tab0[j];
                        tmp1 = tab1[j];
                        tab0[j] = MULL(tmp0 + tmp1, ISQRT2);
                        tab1[j] = MULL(tmp0 - tmp1, ISQRT2);
                    }
                }
            }
        }
    } else if (s->mode_ext & MODE_EXT_MS_STEREO) {
        /* ms stereo ONLY */
        /* NOTE: the 1/sqrt(2) normalization factor is included in the
           global gain */
        tab0 = g0->sb_hybrid;
        tab1 = g1->sb_hybrid;
        for(i=0;i<576;i++) {
            tmp0 = tab0[i];
            tmp1 = tab1[i];
            tab0[i] = tmp0 + tmp1;
            tab1[i] = tmp0 - tmp1;
        }
    }
}

static void compute_antialias(MPADecodeContext *s,
                              GranuleDef *g)
{
    int32_t *ptr, *p0, *p1, *csa;
    int n, tmp0, tmp1, i, j;

    /* we antialias only "long" bands */
    if (g->block_type == 2) {
        if (!g->switch_point)
            return;
        /* XXX: check this for 8000Hz case */
        n = 1;
    } else {
        n = SBLIMIT - 1;
    }
    
    ptr = g->sb_hybrid + 18;
    for(i = n;i > 0;i--) {
        p0 = ptr - 1;
        p1 = ptr;
        csa = &csa_table[0][0];
        for(j=0;j<8;j++) {
            tmp0 = *p0;
            tmp1 = *p1;
            *p0 = FRAC_RND(MUL64(tmp0, csa[0]) - MUL64(tmp1, csa[1]));
            *p1 = FRAC_RND(MUL64(tmp0, csa[1]) + MUL64(tmp1, csa[0]));
            p0--;
            p1++;
            csa += 2;
        }
        ptr += 18;
    }
}

static void compute_imdct(MPADecodeContext *s,
                          GranuleDef *g, 
                          int32_t *sb_samples,
                          int32_t *mdct_buf)
{
    int32_t *ptr, *win, *win1, *buf, *buf2, *out_ptr, *ptr1;
    int32_t in[6];
    int32_t out[36];
    int32_t out2[12];
    int i, j, k, mdct_long_end, v, sblimit;

    /* find last non zero block */
    ptr = g->sb_hybrid + 576;
    ptr1 = g->sb_hybrid + 2 * 18;
    while (ptr >= ptr1) {
        ptr -= 6;
        v = ptr[0] | ptr[1] | ptr[2] | ptr[3] | ptr[4] | ptr[5];
        if (v != 0)
            break;
    }
    sblimit = ((ptr - g->sb_hybrid) / 18) + 1;

    if (g->block_type == 2) {
        /* XXX: check for 8000 Hz */
        if (g->switch_point)
            mdct_long_end = 2;
        else
            mdct_long_end = 0;
    } else {
        mdct_long_end = sblimit;
    }

    buf = mdct_buf;
    ptr = g->sb_hybrid;
    for(j=0;j<mdct_long_end;j++) {
        imdct36(out, ptr);
        /* apply window & overlap with previous buffer */
        out_ptr = sb_samples + j;
        /* select window */
        if (g->switch_point && j < 2)
            win1 = mdct_win[0];
        else
            win1 = mdct_win[g->block_type];
        /* select frequency inversion */
        win = win1 + ((4 * 36) & -(j & 1));
        for(i=0;i<18;i++) {
            *out_ptr = MULL(out[i], win[i]) + buf[i];
            buf[i] = MULL(out[i + 18], win[i + 18]);
            out_ptr += SBLIMIT;
        }
        ptr += 18;
        buf += 18;
    }
    for(j=mdct_long_end;j<sblimit;j++) {
        for(i=0;i<6;i++) {
            out[i] = 0;
            out[6 + i] = 0;
            out[30+i] = 0;
        }
        /* select frequency inversion */
        win = mdct_win[2] + ((4 * 36) & -(j & 1));
        buf2 = out + 6;
        for(k=0;k<3;k++) {
            /* reorder input for short mdct */
            ptr1 = ptr + k;
            for(i=0;i<6;i++) {
                in[i] = *ptr1;
                ptr1 += 3;
            }
            imdct12(out2, in);
            /* apply 12 point window and do small overlap */
            for(i=0;i<6;i++) {
                buf2[i] = MULL(out2[i], win[i]) + buf2[i];
                buf2[i + 6] = MULL(out2[i + 6], win[i + 6]);
            }
            buf2 += 6;
        }
        /* overlap */
        out_ptr = sb_samples + j;
        for(i=0;i<18;i++) {
            *out_ptr = out[i] + buf[i];
            buf[i] = out[i + 18];
            out_ptr += SBLIMIT;
        }
        ptr += 18;
        buf += 18;
    }
    /* zero bands */
    for(j=sblimit;j<SBLIMIT;j++) {
        /* overlap */
        out_ptr = sb_samples + j;
        for(i=0;i<18;i++) {
            *out_ptr = buf[i];
            buf[i] = 0;
            out_ptr += SBLIMIT;
        }
        buf += 18;
    }
}

#if defined(DEBUG)
void sample_dump(int fnum, int32_t *tab, int n)
{
    static FILE *files[16], *f;
    char buf[512];
    int i;
    int32_t v;
    
    f = files[fnum];
    if (!f) {
        sprintf(buf, "/tmp/out%d.%s.pcm", 
                fnum, 
#ifdef USE_HIGHPRECISION
                "hp"
#else
                "lp"
#endif
                );
        f = fopen(buf, "w");
        if (!f)
            return;
        files[fnum] = f;
    }
    
    if (fnum == 0) {
        static int pos = 0;
        printf("pos=%d\n", pos);
        for(i=0;i<n;i++) {
            printf(" %0.4f", (double)tab[i] / FRAC_ONE);
            if ((i % 18) == 17)
                printf("\n");
        }
        pos += n;
    }
    for(i=0;i<n;i++) {
        /* normalize to 23 frac bits */
        v = tab[i] << (23 - FRAC_BITS);
        fwrite(&v, 1, sizeof(int32_t), f);
    }
}
#endif


/* main layer3 decoding function */
static int mp_decode_layer3(MPADecodeContext *s)
{
    int nb_granules, main_data_begin, private_bits;
    int gr, ch, blocksplit_flag, i, j, k, n, bits_pos, bits_left;
    GranuleDef granules[2][2], *g;
    int16_t exponents[576];

    /* read side info */
    if (s->lsf) {
        main_data_begin = get_bits(&s->gb, 8);
        if (s->nb_channels == 2)
            private_bits = get_bits(&s->gb, 2);
        else
            private_bits = get_bits(&s->gb, 1);
        nb_granules = 1;
    } else {
        main_data_begin = get_bits(&s->gb, 9);
        if (s->nb_channels == 2)
            private_bits = get_bits(&s->gb, 3);
        else
            private_bits = get_bits(&s->gb, 5);
        nb_granules = 2;
        for(ch=0;ch<s->nb_channels;ch++) {
            granules[ch][0].scfsi = 0; /* all scale factors are transmitted */
            granules[ch][1].scfsi = get_bits(&s->gb, 4);
        }
    }
    
    for(gr=0;gr<nb_granules;gr++) {
        for(ch=0;ch<s->nb_channels;ch++) {
            dprintf("gr=%d ch=%d: side_info\n", gr, ch);
            g = &granules[ch][gr];
            g->part2_3_length = get_bits(&s->gb, 12);
            g->big_values = get_bits(&s->gb, 9);
            g->global_gain = get_bits(&s->gb, 8);
            /* if MS stereo only is selected, we precompute the
               1/sqrt(2) renormalization factor */
            if ((s->mode_ext & (MODE_EXT_MS_STEREO | MODE_EXT_I_STEREO)) == 
                MODE_EXT_MS_STEREO)
                g->global_gain -= 2;
            if (s->lsf)
                g->scalefac_compress = get_bits(&s->gb, 9);
            else
                g->scalefac_compress = get_bits(&s->gb, 4);
            blocksplit_flag = get_bits(&s->gb, 1);
            if (blocksplit_flag) {
                g->block_type = get_bits(&s->gb, 2);
                if (g->block_type == 0)
                    return -1;
                g->switch_point = get_bits(&s->gb, 1);
                for(i=0;i<2;i++)
                    g->table_select[i] = get_bits(&s->gb, 5);
                for(i=0;i<3;i++) 
                    g->subblock_gain[i] = get_bits(&s->gb, 3);
                /* compute huffman coded region sizes */
                if (g->block_type == 2)
                    g->region_size[0] = (36 / 2);
                else {
                    if (s->sample_rate_index <= 2) 
                        g->region_size[0] = (36 / 2);
                    else if (s->sample_rate_index != 8) 
                        g->region_size[0] = (54 / 2);
                    else
                        g->region_size[0] = (108 / 2);
                }
                g->region_size[1] = (576 / 2);
            } else {
                int region_address1, region_address2, l;
                g->block_type = 0;
                g->switch_point = 0;
                for(i=0;i<3;i++)
                    g->table_select[i] = get_bits(&s->gb, 5);
                /* compute huffman coded region sizes */
                region_address1 = get_bits(&s->gb, 4);
                region_address2 = get_bits(&s->gb, 3);
                dprintf("region1=%d region2=%d\n", 
                        region_address1, region_address2);
                g->region_size[0] = 
                    band_index_long[s->sample_rate_index][region_address1 + 1] >> 1;
                l = region_address1 + region_address2 + 2;
                /* should not overflow */
                if (l > 22)
                    l = 22;
                g->region_size[1] = 
                    band_index_long[s->sample_rate_index][l] >> 1;
            }
            /* convert region offsets to region sizes and truncate
               size to big_values */
            g->region_size[2] = (576 / 2);
            j = 0;
            for(i=0;i<3;i++) {
                k = g->region_size[i];
                if (k > g->big_values)
                    k = g->big_values;
                g->region_size[i] = k - j;
                j = k;
            }

            /* compute band indexes */
            if (g->block_type == 2) {
                if (g->switch_point) {
                    /* if switched mode, we handle the 36 first samples as
                       long blocks.  For 8000Hz, we handle the 48 first
                       exponents as long blocks (XXX: check this!) */
                    if (s->sample_rate_index <= 2)
                        g->long_end = 8;
                    else if (s->sample_rate_index != 8)
                        g->long_end = 6;
                    else
                        g->long_end = 4; /* 8000 Hz */
                    
                    if (s->sample_rate_index != 8)
                        g->short_start = 3;
                    else
                        g->short_start = 2; 
                } else {
                    g->long_end = 0;
                    g->short_start = 0;
                }
            } else {
                g->short_start = 13;
                g->long_end = 22;
            }
            
            g->preflag = 0;
            if (!s->lsf)
                g->preflag = get_bits(&s->gb, 1);
            g->scalefac_scale = get_bits(&s->gb, 1);
            g->count1table_select = get_bits(&s->gb,