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Diffstat (limited to 'contrib/ffmpeg/libavcodec/mdct.c')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/mdct.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/mdct.c b/contrib/ffmpeg/libavcodec/mdct.c new file mode 100644 index 000000000..de3275289 --- /dev/null +++ b/contrib/ffmpeg/libavcodec/mdct.c @@ -0,0 +1,177 @@ +/* + * 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. + */ + +/** + * 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 (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) \ +{\ + 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; + } + ff_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]); + } + + ff_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); + ff_fft_end(&s->fft); +} |