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libavcodec/mdct.c

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00001 /*
00002  * MDCT/IMDCT transforms
00003  * Copyright (c) 2002 Fabrice Bellard
00004  *
00005  * This file is part of Libav.
00006  *
00007  * Libav is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * Libav is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with Libav; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include <stdlib.h>
00023 #include <string.h>
00024 #include "libavutil/common.h"
00025 #include "libavutil/mathematics.h"
00026 #include "fft.h"
00027 #include "fft-internal.h"
00028 
00034 #if CONFIG_FFT_FLOAT
00035 #   define RSCALE(x) (x)
00036 #else
00037 #   define RSCALE(x) ((x) >> 1)
00038 #endif
00039 
00043 av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
00044 {
00045     int n, n4, i;
00046     double alpha, theta;
00047     int tstep;
00048 
00049     memset(s, 0, sizeof(*s));
00050     n = 1 << nbits;
00051     s->mdct_bits = nbits;
00052     s->mdct_size = n;
00053     n4 = n >> 2;
00054     s->mdct_permutation = FF_MDCT_PERM_NONE;
00055 
00056     if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
00057         goto fail;
00058 
00059     s->tcos = av_malloc(n/2 * sizeof(FFTSample));
00060     if (!s->tcos)
00061         goto fail;
00062 
00063     switch (s->mdct_permutation) {
00064     case FF_MDCT_PERM_NONE:
00065         s->tsin = s->tcos + n4;
00066         tstep = 1;
00067         break;
00068     case FF_MDCT_PERM_INTERLEAVE:
00069         s->tsin = s->tcos + 1;
00070         tstep = 2;
00071         break;
00072     default:
00073         goto fail;
00074     }
00075 
00076     theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
00077     scale = sqrt(fabs(scale));
00078     for(i=0;i<n4;i++) {
00079         alpha = 2 * M_PI * (i + theta) / n;
00080         s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
00081         s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);
00082     }
00083     return 0;
00084  fail:
00085     ff_mdct_end(s);
00086     return -1;
00087 }
00088 
00095 void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)
00096 {
00097     int k, n8, n4, n2, n, j;
00098     const uint16_t *revtab = s->revtab;
00099     const FFTSample *tcos = s->tcos;
00100     const FFTSample *tsin = s->tsin;
00101     const FFTSample *in1, *in2;
00102     FFTComplex *z = (FFTComplex *)output;
00103 
00104     n = 1 << s->mdct_bits;
00105     n2 = n >> 1;
00106     n4 = n >> 2;
00107     n8 = n >> 3;
00108 
00109     /* pre rotation */
00110     in1 = input;
00111     in2 = input + n2 - 1;
00112     for(k = 0; k < n4; k++) {
00113         j=revtab[k];
00114         CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
00115         in1 += 2;
00116         in2 -= 2;
00117     }
00118     s->fft_calc(s, z);
00119 
00120     /* post rotation + reordering */
00121     for(k = 0; k < n8; k++) {
00122         FFTSample r0, i0, r1, i1;
00123         CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
00124         CMUL(r1, i0, z[n8+k  ].im, z[n8+k  ].re, tsin[n8+k  ], tcos[n8+k  ]);
00125         z[n8-k-1].re = r0;
00126         z[n8-k-1].im = i0;
00127         z[n8+k  ].re = r1;
00128         z[n8+k  ].im = i1;
00129     }
00130 }
00131 
00137 void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
00138 {
00139     int k;
00140     int n = 1 << s->mdct_bits;
00141     int n2 = n >> 1;
00142     int n4 = n >> 2;
00143 
00144     ff_imdct_half_c(s, output+n4, input);
00145 
00146     for(k = 0; k < n4; k++) {
00147         output[k] = -output[n2-k-1];
00148         output[n-k-1] = output[n2+k];
00149     }
00150 }
00151 
00157 void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)
00158 {
00159     int i, j, n, n8, n4, n2, n3;
00160     FFTDouble re, im;
00161     const uint16_t *revtab = s->revtab;
00162     const FFTSample *tcos = s->tcos;
00163     const FFTSample *tsin = s->tsin;
00164     FFTComplex *x = (FFTComplex *)out;
00165 
00166     n = 1 << s->mdct_bits;
00167     n2 = n >> 1;
00168     n4 = n >> 2;
00169     n8 = n >> 3;
00170     n3 = 3 * n4;
00171 
00172     /* pre rotation */
00173     for(i=0;i<n8;i++) {
00174         re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
00175         im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);
00176         j = revtab[i];
00177         CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
00178 
00179         re = RSCALE( input[2*i]    - input[n2-1-2*i]);
00180         im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);
00181         j = revtab[n8 + i];
00182         CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
00183     }
00184 
00185     s->fft_calc(s, x);
00186 
00187     /* post rotation */
00188     for(i=0;i<n8;i++) {
00189         FFTSample r0, i0, r1, i1;
00190         CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
00191         CMUL(i0, r1, x[n8+i  ].re, x[n8+i  ].im, -tsin[n8+i  ], -tcos[n8+i  ]);
00192         x[n8-i-1].re = r0;
00193         x[n8-i-1].im = i0;
00194         x[n8+i  ].re = r1;
00195         x[n8+i  ].im = i1;
00196     }
00197 }
00198 
00199 av_cold void ff_mdct_end(FFTContext *s)
00200 {
00201     av_freep(&s->tcos);
00202     ff_fft_end(s);
00203 }
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