ac3_imdct.c

vlc stand 0.1.99 ist sehr einfach

/*****************************************************************************
 * ac3_imdct.c: ac3 DCT
 *****************************************************************************
 * Copyright (C) 1999, 2000 VideoLAN
 *
 * Authors:
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/
#include "defs.h"

#include <math.h>

#include "int_types.h"
#include "ac3_decoder.h"
#include "ac3_internal.h"

void imdct_do_256(float x[],float y[],float delay[]);
void imdct_do_512(float x[],float y[],float delay[]);

typedef struct complex_s {
    float real;
    float imag;
} complex_t;

#define N 512

static complex_t buf[N/4];

/* 128 point bit-reverse LUT */
static u8 bit_reverse_512[] = {
    0x00, 0x40, 0x20, 0x60, 0x10, 0x50, 0x30, 0x70,
    0x08, 0x48, 0x28, 0x68, 0x18, 0x58, 0x38, 0x78,
    0x04, 0x44, 0x24, 0x64, 0x14, 0x54, 0x34, 0x74,
    0x0c, 0x4c, 0x2c, 0x6c, 0x1c, 0x5c, 0x3c, 0x7c,
    0x02, 0x42, 0x22, 0x62, 0x12, 0x52, 0x32, 0x72,
    0x0a, 0x4a, 0x2a, 0x6a, 0x1a, 0x5a, 0x3a, 0x7a,
    0x06, 0x46, 0x26, 0x66, 0x16, 0x56, 0x36, 0x76,
    0x0e, 0x4e, 0x2e, 0x6e, 0x1e, 0x5e, 0x3e, 0x7e,
    0x01, 0x41, 0x21, 0x61, 0x11, 0x51, 0x31, 0x71,
    0x09, 0x49, 0x29, 0x69, 0x19, 0x59, 0x39, 0x79,
    0x05, 0x45, 0x25, 0x65, 0x15, 0x55, 0x35, 0x75,
    0x0d, 0x4d, 0x2d, 0x6d, 0x1d, 0x5d, 0x3d, 0x7d,
    0x03, 0x43, 0x23, 0x63, 0x13, 0x53, 0x33, 0x73,
    0x0b, 0x4b, 0x2b, 0x6b, 0x1b, 0x5b, 0x3b, 0x7b,
    0x07, 0x47, 0x27, 0x67, 0x17, 0x57, 0x37, 0x77,
    0x0f, 0x4f, 0x2f, 0x6f, 0x1f, 0x5f, 0x3f, 0x7f};

static u8 bit_reverse_256[] = {
    0x00, 0x20, 0x10, 0x30, 0x08, 0x28, 0x18, 0x38,
    0x04, 0x24, 0x14, 0x34, 0x0c, 0x2c, 0x1c, 0x3c,
    0x02, 0x22, 0x12, 0x32, 0x0a, 0x2a, 0x1a, 0x3a,
    0x06, 0x26, 0x16, 0x36, 0x0e, 0x2e, 0x1e, 0x3e,
    0x01, 0x21, 0x11, 0x31, 0x09, 0x29, 0x19, 0x39,
    0x05, 0x25, 0x15, 0x35, 0x0d, 0x2d, 0x1d, 0x3d,
    0x03, 0x23, 0x13, 0x33, 0x0b, 0x2b, 0x1b, 0x3b,
    0x07, 0x27, 0x17, 0x37, 0x0f, 0x2f, 0x1f, 0x3f};

/* Twiddle factor LUT */
static complex_t *w[7];
static complex_t w_1[1];
static complex_t w_2[2];
static complex_t w_4[4];
static complex_t w_8[8];
static complex_t w_16[16];
static complex_t w_32[32];
static complex_t w_64[64];

/* Twiddle factors for IMDCT */
static float xcos1[N/4];
static float xsin1[N/4];
static float xcos2[N/8];
static float xsin2[N/8];

/* Delay buffer for time domain interleaving */
static float delay[6][256];

/* Windowing function for Modified DCT - Thank you acroread */
static float window[] = {
    0.00014, 0.00024, 0.00037, 0.00051, 0.00067, 0.00086, 0.00107, 0.00130,
    0.00157, 0.00187, 0.00220, 0.00256, 0.00297, 0.00341, 0.00390, 0.00443,
    0.00501, 0.00564, 0.00632, 0.00706, 0.00785, 0.00871, 0.00962, 0.01061,
    0.01166, 0.01279, 0.01399, 0.01526, 0.01662, 0.01806, 0.01959, 0.02121,
    0.02292, 0.02472, 0.02662, 0.02863, 0.03073, 0.03294, 0.03527, 0.03770,
    0.04025, 0.04292, 0.04571, 0.04862, 0.05165, 0.05481, 0.05810, 0.06153,
    0.06508, 0.06878, 0.07261, 0.07658, 0.08069, 0.08495, 0.08935, 0.09389,
    0.09859, 0.10343, 0.10842, 0.11356, 0.11885, 0.12429, 0.12988, 0.13563,
    0.14152, 0.14757, 0.15376, 0.16011, 0.16661, 0.17325, 0.18005, 0.18699,
    0.19407, 0.20130, 0.20867, 0.21618, 0.22382, 0.23161, 0.23952, 0.24757,
    0.25574, 0.26404, 0.27246, 0.28100, 0.28965, 0.29841, 0.30729, 0.31626,
    0.32533, 0.33450, 0.34376, 0.35311, 0.36253, 0.37204, 0.38161, 0.39126,
    0.40096, 0.41072, 0.42054, 0.43040, 0.44030, 0.45023, 0.46020, 0.47019,
    0.48020, 0.49022, 0.50025, 0.51028, 0.52031, 0.53033, 0.54033, 0.55031,
    0.56026, 0.57019, 0.58007, 0.58991, 0.59970, 0.60944, 0.61912, 0.62873,
    0.63827, 0.64774, 0.65713, 0.66643, 0.67564, 0.68476, 0.69377, 0.70269,
    0.71150, 0.72019, 0.72877, 0.73723, 0.74557, 0.75378, 0.76186, 0.76981,
    0.77762, 0.78530, 0.79283, 0.80022, 0.80747, 0.81457, 0.82151, 0.82831,
    0.83496, 0.84145, 0.84779, 0.85398, 0.86001, 0.86588, 0.87160, 0.87716,
    0.88257, 0.88782, 0.89291, 0.89785, 0.90264, 0.90728, 0.91176, 0.91610,
    0.92028, 0.92432, 0.92822, 0.93197, 0.93558, 0.93906, 0.94240, 0.94560,
    0.94867, 0.95162, 0.95444, 0.95713, 0.95971, 0.96217, 0.96451, 0.96674,
    0.96887, 0.97089, 0.97281, 0.97463, 0.97635, 0.97799, 0.97953, 0.98099,
    0.98236, 0.98366, 0.98488, 0.98602, 0.98710, 0.98811, 0.98905, 0.98994,
    0.99076, 0.99153, 0.99225, 0.99291, 0.99353, 0.99411, 0.99464, 0.99513,
    0.99558, 0.99600, 0.99639, 0.99674, 0.99706, 0.99736, 0.99763, 0.99788,
    0.99811, 0.99831, 0.99850, 0.99867, 0.99882, 0.99895, 0.99908, 0.99919,
    0.99929, 0.99938, 0.99946, 0.99953, 0.99959, 0.99965, 0.99969, 0.99974,
    0.99978, 0.99981, 0.99984, 0.99986, 0.99988, 0.99990, 0.99992, 0.99993,
    0.99994, 0.99995, 0.99996, 0.99997, 0.99998, 0.99998, 0.99998, 0.99999,
    0.99999, 0.99999, 0.99999, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000,
    1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000, 1.00000 };

static __inline__ void swap_cmplx(complex_t *a, complex_t *b)
{
    complex_t tmp;

    tmp = *a;
    *a = *b;
    *b = tmp;
}

static __inline__ complex_t cmplx_mult(complex_t a, complex_t b)
{
    complex_t ret;

    ret.real = a.real * b.real - a.imag * b.imag;
    ret.imag = a.real * b.imag + a.imag * b.real;

    return ret;
}

static void imdct_init(void) __attribute__ ((__constructor__));
static void imdct_init(void)
{
    int i,k;
    complex_t angle_step;
    complex_t current_angle;

    /* Twiddle factors to turn IFFT into IMDCT */
    for (i=0; i < N/4; i++) {
        xcos1[i] = -cos(2 * M_PI * (8*i+1)/(8*N)) ;
        xsin1[i] = -sin(2 * M_PI * (8*i+1)/(8*N)) ;
    }

    /* More twiddle factors to turn IFFT into IMDCT */
    for (i=0; i < N/8; i++) {
        xcos2[i] = -cos(2 * M_PI * (8*i+1)/(4*N)) ;
        xsin2[i] = -sin(2 * M_PI * (8*i+1)/(4*N)) ;
    }

    /* Canonical twiddle factors for FFT */
    w[0] = w_1;
    w[1] = w_2;
    w[2] = w_4;
    w[3] = w_8;
    w[4] = w_16;
    w[5] = w_32;
    w[6] = w_64;

    for (i = 0; i < 7; i++) {
        angle_step.real = cos(-2.0f * M_PI / (1 << (i+1)));
        angle_step.imag = sin(-2.0f * M_PI / (1 << (i+1)));

        current_angle.real = 1.0f;
        current_angle.imag = 0.0f;

        for (k = 0; k < 1 << i; k++) {
            w[i][k] = current_angle;
            current_angle = cmplx_mult(current_angle,angle_step);
        }
    }
}

void imdct (ac3dec_t * p_ac3dec)
{
    int i;

    for (i=0; i<p_ac3dec->bsi.nfchans;i++) {
        if (p_ac3dec->audblk.blksw[i])
            imdct_do_256(p_ac3dec->coeffs.fbw[i],p_ac3dec->samples.channel[i],delay[i]);
        else
            imdct_do_512(p_ac3dec->coeffs.fbw[i],p_ac3dec->samples.channel[i],delay[i]);
    }

    /* XXX?? We don't bother with the IMDCT for the LFE as it's currently
     * unused. */
    //if (bsi->lfeon)
    //    imdct_do_512(coeffs->lfe,samples->channel[5],delay[5]);
}

void
imdct_do_512(float x[],float y[],float delay[])
{
    int i,k;
    int p,q;
    int m;
    int two_m;
    int two_m_plus_one;

    float tmp_a_i;
    float tmp_a_r;
    float tmp_b_i;
    float tmp_b_r;


    float *y_ptr;
    float *delay_ptr;
    float *window_ptr;

    /* Pre IFFT complex multiply plus IFFT cmplx conjugate */
    for (i=0; i < N/4; i++) {
        /* z[i] = (X[N/2-2*i-1] + j * X[2*i]) * (xcos1[i] + j * xsin1[i]) ; */
        buf[i].real =  (x[N/2-2*i-1] * xcos1[i])  - (x[2*i]       * xsin1[i]);
        buf[i].imag = -((x[2*i]       * xcos1[i])  + (x[N/2-2*i-1] * xsin1[i]));
    }

    /* Bit reversed shuffling */
    for (i=0; i<N/4; i++) {
        k = bit_reverse_512[i];
        if (k < i)
            swap_cmplx(&buf[i],&buf[k]);
    }

    /* FFT Merge */
    for (m=0; m < 7; m++) {
        two_m = (1 << m);
        two_m_plus_one = (1 << (m+1));

        for (k = 0; k < two_m; k++) {
            for (i = 0; i < 128; i += two_m_plus_one) {
                p = k + i;
                q = p + two_m;
                tmp_a_r = buf[p].real;
                tmp_a_i = buf[p].imag;
                tmp_b_r = buf[q].real * w[m][k].real - buf[q].imag * w[m][k].imag;
                tmp_b_i = buf[q].imag * w[m][k].real + buf[q].real * w[m][k].imag;
                buf[p].real = tmp_a_r + tmp_b_r;
                buf[p].imag =  tmp_a_i + tmp_b_i;
                buf[q].real = tmp_a_r - tmp_b_r;
                buf[q].imag =  tmp_a_i - tmp_b_i;
            }
        }
    }

    /* Post IFFT complex multiply  plus IFFT complex conjugate*/
    for (i=0; i < N/4; i++) {
        /* y[n] = z[n] * (xcos1[n] + j * xsin1[n]) ; */
        tmp_a_r =   buf[i].real;
        tmp_a_i = - buf[i].imag;
        buf[i].real =(tmp_a_r * xcos1[i])  - (tmp_a_i  * xsin1[i]);
        buf[i].imag =(tmp_a_r * xsin1[i])  + (tmp_a_i  * xcos1[i]);
    }

    y_ptr = y;
    delay_ptr = delay;
    window_ptr = window;
    /* Window and convert to real valued signal */
    for (i=0; i<N/8; i++) {
        *y_ptr++   = 2.0f * (-buf[N/8+i].imag   * *window_ptr++ + *delay_ptr++);
        *y_ptr++   = 2.0f * (buf[N/8-i-1].real * *window_ptr++ + *delay_ptr++);
    }

    for (i=0; i<N/8; i++) {
        *y_ptr++  = 2.0f * (-buf[i].real       * *window_ptr++ + *delay_ptr++);
        *y_ptr++  = 2.0f * (buf[N/4-i-1].imag * *window_ptr++ + *delay_ptr++);
    }

    /* The trailing edge of the window goes into the delay line */
    delay_ptr = delay;

    for (i=0; i<N/8; i++) {
        *delay_ptr++  = -buf[N/8+i].real   * *--window_ptr;
        *delay_ptr++  =  buf[N/8-i-1].imag * *--window_ptr;
    }

    for (i=0; i<N/8; i++) {
        *delay_ptr++  =  buf[i].imag       * *--window_ptr;
        *delay_ptr++  = -buf[N/4-i-1].real * *--window_ptr;
    }
}

void
imdct_do_256(float x[],float y[],float delay[])
{
    int i,k;
    int p,q;
    int m;
    int two_m;
    int two_m_plus_one;

    float tmp_a_i;
    float tmp_a_r;
    float tmp_b_i;
    float tmp_b_r;

    complex_t *buf_1, *buf_2;

    buf_1 = &buf[0];
    buf_2 = &buf[64];

    /* Pre IFFT complex multiply plus IFFT cmplx conjugate */
    for (k=0; k<N/8; k++) {
        /* X1[k] = X[2*k]  */
        /* X2[k] = X[2*k+1]     */

        p = 2 * (N/4-2*k-1);
        q = 2 * (2 * k);

       /* Z1[k] = (X1[N/4-2*k-1] + j * X1[2*k]) * (xcos2[k] + j * xsin2[k]); */
        buf_1[k].real =    x[p] * xcos2[k] - x[q] * xsin2[k];
        buf_1[k].imag = - (x[q] * xcos2[k] + x[p] * xsin2[k]);
       /* Z2[k] = (X2[N/4-2*k-1] + j * X2[2*k]) * (xcos2[k] + j * xsin2[k]); */
        buf_2[k].real =    x[p + 1] * xcos2[k] - x[q + 1] * xsin2[k];
        buf_2[k].imag = - (x[q + 1] * xcos2[k] + x[p + 1] * xsin2[k]);
    }

    /* IFFT Bit reversed shuffling */
    for (i=0; i<N/8; i++) {
        k = bit_reverse_256[i];
        if (k < i) {
            swap_cmplx(&buf_1[i],&buf_1[k]);
            swap_cmplx(&buf_2[i],&buf_2[k]);
        }
    }

    /* FFT Merge */
    for (m=0; m < 6; m++) {
        two_m = (1 << m);
        two_m_plus_one = (1 << (m+1));

        for (k = 0; k < two_m; k++) {
            for (i = 0; i < 64; i += two_m_plus_one) {
                p = k + i;
                q = p + two_m;
                /* Do block 1 */
                tmp_a_r = buf_1[p].real;
                tmp_a_i = buf_1[p].imag;
                tmp_b_r = buf_1[q].real * w[m][k].real - buf_1[q].imag * w[m][k].imag;
                tmp_b_i = buf_1[q].imag * w[m][k].real + buf_1[q].real * w[m][k].imag;
                buf_1[p].real = tmp_a_r + tmp_b_r;
                buf_1[p].imag =  tmp_a_i + tmp_b_i;
                buf_1[q].real = tmp_a_r - tmp_b_r;
                buf_1[q].imag =  tmp_a_i - tmp_b_i;

                /* Do block 2 */
                tmp_a_r = buf_2[p].real;
                tmp_a_i = buf_2[p].imag;
                tmp_b_r = buf_2[q].real * w[m][k].real - buf_2[q].imag * w[m][k].imag;
                tmp_b_i = buf_2[q].imag * w[m][k].real + buf_2[q].real * w[m][k].imag;
                buf_2[p].real = tmp_a_r + tmp_b_r;
                buf_2[p].imag =  tmp_a_i + tmp_b_i;
                buf_2[q].real = tmp_a_r - tmp_b_r;
                buf_2[q].imag =  tmp_a_i - tmp_b_i;
            }
        }
    }

    /* Post IFFT complex multiply */
    for (i=0; i < N/8; i++) {
        /* y1[n] = z1[n] * (xcos2[n] + j * xs in2[n]) ; */
        tmp_a_r =   buf_1[i].real;
        tmp_a_i = - buf_1[i].imag;
        buf_1[i].real =(tmp_a_r * xcos2[i])  - (tmp_a_i  * xsin2[i]);
        buf_1[i].imag =(tmp_a_r * xsin2[i])  + (tmp_a_i  * xcos2[i]);
        /* y2[n] = z2[n] * (xcos2[n] + j * xsin2[n]) ; */
        tmp_a_r =   buf_2[i].real;
        tmp_a_i = - buf_2[i].imag;
        buf_2[i].real =(tmp_a_r * xcos2[i])  - (tmp_a_i  * xsin2[i]);
        buf_2[i].imag =(tmp_a_r * xsin2[i])  + (tmp_a_i  * xcos2[i]);
    }

    /* Window and convert to real valued signal */
    for (i=0; i<N/8; i++) {
        y[2*i]         = -buf_1[i].imag       * window[2*i];
        y[2*i+1]       =  buf_1[N/8-i-1].real * window[2*i+1];
        y[N/4+2*i]     = -buf_1[i].real       * window[N/4+2*i];
        y[N/4+2*i+1]   =  buf_1[N/8-i-1].imag * window[N/4+2*i+1];
        y[N/2+2*i]     = -buf_2[i].real       * window[N/2-2*i-1];
        y[N/2+2*i+1]   =  buf_2[N/8-i-1].imag * window[N/2-2*i-2];
        y[3*N/4+2*i]   =  buf_2[i].imag       * window[N/4-2*i-1];
        y[3*N/4+2*i+1] = -buf_2[N/8-i-1].real * window[N/4-2*i-2];
    }

    /* Overlap and add */
    for (i=0; i<N/2; i++) {
        y[i] = 2 * (y[i] + delay[i]);
        delay[i] = y[N/2+i];
    }
}