wmadec.c

tcpmp播放器的flv插件

                tprintf(" %d", s->exponent_bands[i][j]);
            tprintf("\n");
        }
    }
#endif

    /* init MDCT */
    for(i = 0; i < s->nb_block_sizes; i++)
        ff_mdct_init(&s->mdct_ctx[i], s->frame_len_bits - i + 1, 1);
    
    /* init MDCT windows : simple sinus window */
    for(i = 0; i < s->nb_block_sizes; i++) {
        int n, j;
        float alpha;
        n = 1 << (s->frame_len_bits - i);
        window = av_malloc(sizeof(float) * n);
        alpha = M_PI / (2.0 * n);
        for(j=0;j<n;j++) {
            window[n - j - 1] = sin((j + 0.5) * alpha);
        }
        s->windows[i] = window;
    }

    s->reset_block_lengths = 1;
    
    if (s->use_noise_coding) {

        /* init the noise generator */
        if (s->use_exp_vlc)
            s->noise_mult = 0.02;
        else
            s->noise_mult = 0.04;
               
#ifdef TRACE
        for(i=0;i<NOISE_TAB_SIZE;i++)
            s->noise_table[i] = 1.0 * s->noise_mult;
#else
        {
            unsigned int seed;
            float norm;
            seed = 1;
            norm = (1.0 / (float)(1LL << 31)) * sqrt(3) * s->noise_mult;
            for(i=0;i<NOISE_TAB_SIZE;i++) {
                seed = seed * 314159 + 1;
                s->noise_table[i] = (float)((int)seed) * norm;
            }
        }
#endif
        init_vlc(&s->hgain_vlc, 9, sizeof(hgain_huffbits), 
                 hgain_huffbits, 1, 1,
                 hgain_huffcodes, 2, 2, 0);
    }

    if (s->use_exp_vlc) {
        init_vlc(&s->exp_vlc, 9, sizeof(scale_huffbits), 
                 scale_huffbits, 1, 1,
                 scale_huffcodes, 4, 4, 0);
    } else {
        wma_lsp_to_curve_init(s, s->frame_len);
    }

    /* choose the VLC tables for the coefficients */
    coef_vlc_table = 2;
    if (s->sample_rate >= 32000) {
        if (bps1 < 0.72)
            coef_vlc_table = 0;
        else if (bps1 < 1.16)
            coef_vlc_table = 1;
    }

    init_coef_vlc(&s->coef_vlc[0], &s->run_table[0], &s->level_table[0],
                  &coef_vlcs[coef_vlc_table * 2]);
    init_coef_vlc(&s->coef_vlc[1], &s->run_table[1], &s->level_table[1],
                  &coef_vlcs[coef_vlc_table * 2 + 1]);
    return 0;
}

/* interpolate values for a bigger or smaller block. The block must
   have multiple sizes */
static void interpolate_array(float *scale, int old_size, int new_size)
{
    int i, j, jincr, k;
    float v;

    if (new_size > old_size) {
        jincr = new_size / old_size;
        j = new_size;
        for(i = old_size - 1; i >=0; i--) {
            v = scale[i];
            k = jincr;
            do {
                scale[--j] = v;
            } while (--k);
        }
    } else if (new_size < old_size) {
        j = 0;
        jincr = old_size / new_size;
        for(i = 0; i < new_size; i++) {
            scale[i] = scale[j];
            j += jincr;
        }
    }
}

/* compute x^-0.25 with an exponent and mantissa table. We use linear
   interpolation to reduce the mantissa table size at a small speed
   expense (linear interpolation approximately doubles the number of
   bits of precision). */
static inline float pow_m1_4(WMADecodeContext *s, float x)
{
    union {
        float f;
        unsigned int v;
    } u, t;
    unsigned int e, m;
    float a, b;

    u.f = x;
    e = u.v >> 23;
    m = (u.v >> (23 - LSP_POW_BITS)) & ((1 << LSP_POW_BITS) - 1);
    /* build interpolation scale: 1 <= t < 2. */
    t.v = ((u.v << LSP_POW_BITS) & ((1 << 23) - 1)) | (127 << 23);
    a = s->lsp_pow_m_table1[m];
    b = s->lsp_pow_m_table2[m];
    return s->lsp_pow_e_table[e] * (a + b * t.f);
}

static void wma_lsp_to_curve_init(WMADecodeContext *s, int frame_len)
{  
    float wdel, a, b;
    int i, e, m;

    wdel = M_PI / frame_len;
    for(i=0;i<frame_len;i++)
        s->lsp_cos_table[i] = 2.0f * cos(wdel * i);

    /* tables for x^-0.25 computation */
    for(i=0;i<256;i++) {
        e = i - 126;
        s->lsp_pow_e_table[i] = pow(2.0, e * -0.25);
    }

    /* NOTE: these two tables are needed to avoid two operations in
       pow_m1_4 */
    b = 1.0;
    for(i=(1 << LSP_POW_BITS) - 1;i>=0;i--) {
        m = (1 << LSP_POW_BITS) + i;
        a = (float)m * (0.5 / (1 << LSP_POW_BITS));
        a = pow(a, -0.25);
        s->lsp_pow_m_table1[i] = 2 * a - b;
        s->lsp_pow_m_table2[i] = b - a;
        b = a;
    }
#if 0
    for(i=1;i<20;i++) {
        float v, r1, r2;
        v = 5.0 / i;
        r1 = pow_m1_4(s, v);
        r2 = pow(v,-0.25);
        printf("%f^-0.25=%f e=%f\n", v, r1, r2 - r1);
    }
#endif
}

/* NOTE: We use the same code as Vorbis here */
/* XXX: optimize it further with SSE/3Dnow */
static void wma_lsp_to_curve(WMADecodeContext *s, 
                             float *out, float *val_max_ptr, 
                             int n, float *lsp)
{
    int i, j;
    float p, q, w, v, val_max;

    val_max = 0;
    for(i=0;i<n;i++) {
        p = 0.5f;
        q = 0.5f;
        w = s->lsp_cos_table[i];
        for(j=1;j<NB_LSP_COEFS;j+=2){
            q *= w - lsp[j - 1];
            p *= w - lsp[j];
        }
        p *= p * (2.0f - w);
        q *= q * (2.0f + w);
        v = p + q;
        v = pow_m1_4(s, v);
        if (v > val_max)
            val_max = v;
        out[i] = v;
    }
    *val_max_ptr = val_max;
}

/* decode exponents coded with LSP coefficients (same idea as Vorbis) */
static void decode_exp_lsp(WMADecodeContext *s, int ch)
{
    float lsp_coefs[NB_LSP_COEFS];
    int val, i;

    for(i = 0; i < NB_LSP_COEFS; i++) {
        if (i == 0 || i >= 8)
            val = get_bits(&s->gb, 3);
        else
            val = get_bits(&s->gb, 4);
        lsp_coefs[i] = lsp_codebook[i][val];
    }

    wma_lsp_to_curve(s, s->exponents[ch], &s->max_exponent[ch],
                     s->block_len, lsp_coefs);
}

/* decode exponents coded with VLC codes */
static int decode_exp_vlc(WMADecodeContext *s, int ch)
{
    int last_exp, n, code;
    const uint16_t *ptr, *band_ptr;
    float v, *q, max_scale, *q_end;
    
    band_ptr = s->exponent_bands[s->frame_len_bits - s->block_len_bits];
    ptr = band_ptr;
    q = s->exponents[ch];
    q_end = q + s->block_len;
    max_scale = 0;
    if (s->version == 1) {
        last_exp = get_bits(&s->gb, 5) + 10;
        /* XXX: use a table */
        v = pow(10, last_exp * (1.0 / 16.0));
        max_scale = v;
        n = *ptr++;
        do {
            *q++ = v;
        } while (--n);
    }
    last_exp = 36;
    while (q < q_end) {
        code = get_vlc(&s->gb, &s->exp_vlc);
        if (code < 0)
            return -1;
        /* NOTE: this offset is the same as MPEG4 AAC ! */
        last_exp += code - 60;
        /* XXX: use a table */
        v = pow(10, last_exp * (1.0 / 16.0));
        if (v > max_scale)
            max_scale = v;
        n = *ptr++;
        do {
            *q++ = v;
        } while (--n);
    }
    s->max_exponent[ch] = max_scale;
    return 0;
}

/* return 0 if OK. return 1 if last block of frame. return -1 if
   unrecorrable error. */
static int wma_decode_block(WMADecodeContext *s)
{
    int n, v, a, ch, code, bsize;
    int coef_nb_bits, total_gain, parse_exponents;
    float window[BLOCK_MAX_SIZE * 2];
// XXX: FIXME!! there's a bug somewhere which makes this mandatory under altivec
#ifdef HAVE_ALTIVEC
    volatile int nb_coefs[MAX_CHANNELS] __attribute__((aligned(16)));
#else
    int nb_coefs[MAX_CHANNELS];
#endif
    float mdct_norm;

#ifdef TRACE
    tprintf("***decode_block: %d:%d\n", s->frame_count - 1, s->block_num);
#endif

    /* compute current block length */
    if (s->use_variable_block_len) {
        n = av_log2(s->nb_block_sizes - 1) + 1;
    
        if (s->reset_block_lengths) {
            s->reset_block_lengths = 0;
            v = get_bits(&s->gb, n);
            if (v >= s->nb_block_sizes)
                return -1;
            s->prev_block_len_bits = s->frame_len_bits - v;
            v = get_bits(&s->gb, n);
            if (v >= s->nb_block_sizes)
                return -1;
            s->block_len_bits = s->frame_len_bits - v;
        } else {
            /* update block lengths */
            s->prev_block_len_bits = s->block_len_bits;
            s->block_len_bits = s->next_block_len_bits;
        }
        v = get_bits(&s->gb, n);
        if (v >= s->nb_block_sizes)
            return -1;
        s->next_block_len_bits = s->frame_len_bits - v;
    } else {
        /* fixed block len */
        s->next_block_len_bits = s->frame_len_bits;
        s->prev_block_len_bits = s->frame_len_bits;
        s->block_len_bits = s->frame_len_bits;
    }

    /* now check if the block length is coherent with the frame length */
    s->block_len = 1 << s->block_len_bits;
    if ((s->block_pos + s->block_len) > s->frame_len)
        return -1;

    if (s->nb_channels == 2) {
        s->ms_stereo = get_bits(&s->gb, 1);
    }
    v = 0;
    for(ch = 0; ch < s->nb_channels; ch++) {
        a = get_bits(&s->gb, 1);
        s->channel_coded[ch] = a;
        v |= a;
    }
    /* if no channel coded, no need to go further */
    /* XXX: fix potential framing problems */
    if (!v)
        goto next;

    bsize = s->frame_len_bits - s->block_len_bits;

    /* read total gain and extract corresponding number of bits for
       coef escape coding */
    total_gain = 1;
    for(;;) {
        a = get_bits(&s->gb, 7);
        total_gain += a;
        if (a != 127)
            break;
    }
    
    if (total_gain < 15)
        coef_nb_bits = 13;
    else if (total_gain < 32)
        coef_nb_bits = 12;
    else if (total_gain < 40)
        coef_nb_bits = 11;
    else if (total_gain < 45)
        coef_nb_bits = 10;
    else
        coef_nb_bits = 9;

    /* compute number of coefficients */
    n = s->coefs_end[bsize] - s->coefs_start;
    for(ch = 0; ch < s->nb_channels; ch++)
        nb_coefs[ch] = n;

    /* complex coding */
    if (s->use_noise_coding) {

        for(ch = 0; ch < s->nb_channels; ch++) {
            if (s->channel_coded[ch]) {
                int i, n, a;
                n = s->exponent_high_sizes[bsize];
                for(i=0;i<n;i++) {
                    a = get_bits(&s->gb, 1);
                    s->high_band_coded[ch][i] = a;
                    /* if noise coding, the coefficients are not transmitted */
                    if (a)
                        nb_coefs[ch] -= s->exponent_high_bands[bsize][i];
                }
            }
        }
        for(ch = 0; ch < s->nb_channels; ch++) {
            if (s->channel_coded[ch]) {
                int i, n, val, code;

                n = s->exponent_high_sizes[bsize];
                val = (int)0x80000000;
                for(i=0;i<n;i++) {
                    if (s->high_band_coded[ch][i]) {
                        if (val == (int)0x80000000) {
                            val = get_bits(&s->gb, 7) - 19;
                        } else {
                            code = get_vlc(&s->gb, &s->hgain_vlc);
                            if (code < 0)
                                return -1;
                            val += code - 18;
                        }
                        s->high_band_values[ch][i] = val;
                    }
                }
            }
        }
    }
           
    /* exposant can be interpolated in short blocks. */
    parse_exponents = 1;
    if (s->block_len_bits != s->frame_len_bits) {
        parse_exponents = get_bits(&s->gb, 1);
    }
    
    if (parse_exponents) {
        for(ch = 0; ch < s->nb_channels; ch++) {
            if (s->channel_coded[ch]) {
                if (s->use_exp_vlc) {
                    if (decode_exp_vlc(s, ch) < 0)
                        return -1;
                } else {
                    decode_exp_lsp(s, ch);
                }
            }
        }
    } else {
        for(ch = 0; ch < s->nb_channels; ch++) {
            if (s->channel_coded[ch]) {
                interpolate_array(s->exponents[ch], 1 << s->prev_block_len_bits, 
                                  s->block_len);
            }
        }
    }

    /* parse spectral coefficients : just RLE encoding */
    for(ch = 0; ch < s->nb_channels; ch++) {
        if (s->channel_coded[ch]) {
            VLC *coef_vlc;
            int level, run, sign, tindex;
            int16_t *ptr, *eptr;
            const int16_t *level_table, *run_table;

            /* special VLC tables are used for ms stereo because
               there is potentially less energy there */
            tindex = (ch == 1 && s->ms_stereo);
            coef_vlc = &s->coef_vlc[tindex];
            run_table = s->run_table[tindex];
            level_table = s->level_table[tindex];
            /* XXX: optimize */
            ptr = &s->coefs1[ch][0];
            eptr = ptr + nb_coefs[ch];
            memset(ptr, 0, s->block_len * sizeof(int16_t));
            for(;;) {
                code = get_vlc(&s->gb, coef_vlc);
                if (code < 0)
                    return -1;
                if (code == 1) {
                    /* EOB */
                    break;
                } else if (code == 0) {
                    /* escape */
                    level = get_bits(&s->gb, coef_nb_bits);
                    /* NOTE: this is rather suboptimal. reading
                       block_len_bits would be better */
                    run = get_bits(&s->gb, s->frame_len_bits);
                } else {