/* * MDCT/IMDCT transforms * Copyright (c) 2002 Fabrice Bellard. * * This file is part of FFmpeg. * * FFmpeg 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 2.1 of the License, or (at your option) any later version. * * FFmpeg 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 FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "dsputil.h" /** * @file mdct.c * MDCT/IMDCT transforms. */ // Generate a Kaiser-Bessel Derived Window. #define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation void ff_kbd_window_init(float *window, float alpha, int n) { int i, j; double sum = 0.0, bessel, tmp; double local_window[n]; double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n); for (i = 0; i < n; i++) { tmp = i * (n - i) * alpha2; bessel = 1.0; for (j = BESSEL_I0_ITER; j > 0; j--) bessel = bessel * tmp / (j * j) + 1; sum += bessel; local_window[i] = sum; } sum++; for (i = 0; i < n; i++) window[i] = sqrt(local_window[i] / sum); } DECLARE_ALIGNED(16, float, ff_sine_128 [ 128]); DECLARE_ALIGNED(16, float, ff_sine_256 [ 256]); DECLARE_ALIGNED(16, float, ff_sine_512 [ 512]); DECLARE_ALIGNED(16, float, ff_sine_1024[1024]); DECLARE_ALIGNED(16, float, ff_sine_2048[2048]); float *ff_sine_windows[5] = { ff_sine_128, ff_sine_256, ff_sine_512, ff_sine_1024, ff_sine_2048, }; // Generate a sine window. void ff_sine_window_init(float *window, int n) { int i; for(i = 0; i < n; i++) window[i] = sinf((i + 0.5) * (M_PI / (2.0 * n))); } /** * init MDCT or IMDCT computation. */ int ff_mdct_init(MDCTContext *s, int nbits, int inverse) { int n, n4, i; double 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 (ff_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) \ {\ FFTSample _are = (are);\ FFTSample _aim = (aim);\ FFTSample _bre = (bre);\ FFTSample _bim = (bim);\ (pre) = _are * _bre - _aim * _bim;\ (pim) = _are * _bim + _aim * _bre;\ } /** * Compute the middle half of the inverse MDCT of size N = 2^nbits, * thus excluding the parts that can be derived by symmetry * @param output N/2 samples * @param input N/2 samples */ void ff_imdct_half_c(MDCTContext *s, FFTSample *output, const FFTSample *input) { 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 *)output; 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; } ff_fft_calc(&s->fft, z); /* post rotation + reordering */ output += n4; for(k = 0; k < n8; k++) { FFTSample r0, i0, r1, i1; CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); z[n8-k-1].re = r0; z[n8-k-1].im = i0; z[n8+k ].re = r1; z[n8+k ].im = i1; } } /** * 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_c(MDCTContext *s, FFTSample *output, const FFTSample *input) { int k; int n = 1 << s->nbits; int n2 = n >> 1; int n4 = n >> 2; ff_imdct_half_c(s, output+n4, input); for(k = 0; k < n4; k++) { output[k] = -output[n2-k-1]; output[n-k-1] = output[n2+k]; } } /** * 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) { int i, j, n, n8, n4, n2, n3; FFTSample re, im; const uint16_t *revtab = s->fft.revtab; const FFTSample *tcos = s->tcos; const FFTSample *tsin = s->tsin; FFTComplex *x = (FFTComplex *)out; 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]); } ff_fft_calc(&s->fft, x); /* post rotation */ for(i=0;i<n8;i++) { FFTSample r0, i0, r1, i1; CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]); CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]); x[n8-i-1].re = r0; x[n8-i-1].im = i0; x[n8+i ].re = r1; x[n8+i ].im = i1; } } void ff_mdct_end(MDCTContext *s) { av_freep(&s->tcos); av_freep(&s->tsin); ff_fft_end(&s->fft); }