PeerStreamer

/*

 * MDCT/IMDCT transforms

 * Copyright (c) 2002 Fabrice Bellard.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

#include "dsputil.h"

/**

 * @file mdct.c

 * MDCT/IMDCT transforms.

 */

/**

 * init MDCT or IMDCT computation.

 */

int ff_mdct_init(MDCTContext *s, int nbits, int inverse)

{

    int n, n4, i;

    float alpha;

    memset(s, 0, sizeof(*s));

    n = 1 << nbits;

    s->nbits = nbits;

    s->n = n;

    n4 = n >> 2;

    s->tcos = av_malloc(n4 * sizeof(FFTSample));

    if (!s->tcos)

        goto fail;

    s->tsin = av_malloc(n4 * sizeof(FFTSample));

    if (!s->tsin)

        goto fail;

    for(i=0;i<n4;i++) {

        alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;

        s->tcos[i] = -cos(alpha);

        s->tsin[i] = -sin(alpha);

    }

    if (fft_init(&s->fft, s->nbits - 2, inverse) < 0)

        goto fail;

    return 0;

 fail:

    av_freep(&s->tcos);

    av_freep(&s->tsin);

    return -1;

}

/* complex multiplication: p = a * b */

#define CMUL(pre, pim, are, aim, bre, bim) \

{\

    float _are = (are);\

    float _aim = (aim);\

    float _bre = (bre);\

    float _bim = (bim);\

    (pre) = _are * _bre - _aim * _bim;\

    (pim) = _are * _bim + _aim * _bre;\

}

/**

 * Compute inverse MDCT of size N = 2^nbits

 * @param output N samples

 * @param input N/2 samples

 * @param tmp N/2 samples

 */

void ff_imdct_calc(MDCTContext *s, FFTSample *output, 

                   const FFTSample *input, FFTSample *tmp)

{

    int k, n8, n4, n2, n, j;

    const uint16_t *revtab = s->fft.revtab;

    const FFTSample *tcos = s->tcos;

    const FFTSample *tsin = s->tsin;

    const FFTSample *in1, *in2;

    FFTComplex *z = (FFTComplex *)tmp;

    n = 1 << s->nbits;

    n2 = n >> 1;

    n4 = n >> 2;

    n8 = n >> 3;

    /* pre rotation */

    in1 = input;

    in2 = input + n2 - 1;

    for(k = 0; k < n4; k++) {

        j=revtab[k];

        CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);

        in1 += 2;

        in2 -= 2;

    }

    fft_calc(&s->fft, z);

    /* post rotation + reordering */

    /* XXX: optimize */

    for(k = 0; k < n4; k++) {

        CMUL(z[k].re, z[k].im, z[k].re, z[k].im, tcos[k], tsin[k]);

    }

    for(k = 0; k < n8; k++) {

        output[2*k] = -z[n8 + k].im;

        output[n2-1-2*k] = z[n8 + k].im;

        output[2*k+1] = z[n8-1-k].re;

        output[n2-1-2*k-1] = -z[n8-1-k].re;

        output[n2 + 2*k]=-z[k+n8].re;

        output[n-1- 2*k]=-z[k+n8].re;

        output[n2 + 2*k+1]=z[n8-k-1].im;

        output[n-2 - 2 * k] = z[n8-k-1].im;

    }

}

/**

 * Compute MDCT of size N = 2^nbits

 * @param input N samples

 * @param out N/2 samples

 * @param tmp temporary storage of N/2 samples

 */

void ff_mdct_calc(MDCTContext *s, FFTSample *out, 

                  const FFTSample *input, FFTSample *tmp)

{

    int i, j, n, n8, n4, n2, n3;

    FFTSample re, im, re1, im1;

    const uint16_t *revtab = s->fft.revtab;

    const FFTSample *tcos = s->tcos;

    const FFTSample *tsin = s->tsin;

    FFTComplex *x = (FFTComplex *)tmp;

    n = 1 << s->nbits;

    n2 = n >> 1;

    n4 = n >> 2;

    n8 = n >> 3;

    n3 = 3 * n4;

    /* pre rotation */

    for(i=0;i<n8;i++) {

        re = -input[2*i+3*n4] - input[n3-1-2*i];

        im = -input[n4+2*i] + input[n4-1-2*i];

        j = revtab[i];

        CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);

        re = input[2*i] - input[n2-1-2*i];

        im = -(input[n2+2*i] + input[n-1-2*i]);

        j = revtab[n8 + i];

        CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);

    }

    fft_calc(&s->fft, x);

    /* post rotation */

    for(i=0;i<n4;i++) {

        re = x[i].re;

        im = x[i].im;

        CMUL(re1, im1, re, im, -tsin[i], -tcos[i]);

        out[2*i] = im1;

        out[n2-1-2*i] = re1;

    }

}

void ff_mdct_end(MDCTContext *s)

{

    av_freep(&s->tcos);

    av_freep(&s->tsin);

    fft_end(&s->fft);

}