yading@10: /* yading@10: * MDCT/IMDCT transforms yading@10: * Copyright (c) 2002 Fabrice Bellard yading@10: * yading@10: * This file is part of FFmpeg. yading@10: * yading@10: * FFmpeg is free software; you can redistribute it and/or yading@10: * modify it under the terms of the GNU Lesser General Public yading@10: * License as published by the Free Software Foundation; either yading@10: * version 2.1 of the License, or (at your option) any later version. yading@10: * yading@10: * FFmpeg is distributed in the hope that it will be useful, yading@10: * but WITHOUT ANY WARRANTY; without even the implied warranty of yading@10: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU yading@10: * Lesser General Public License for more details. yading@10: * yading@10: * You should have received a copy of the GNU Lesser General Public yading@10: * License along with FFmpeg; if not, write to the Free Software yading@10: * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA yading@10: */ yading@10: yading@10: #include yading@10: #include yading@10: #include "libavutil/common.h" yading@10: #include "libavutil/mathematics.h" yading@10: #include "fft.h" yading@10: #include "fft-internal.h" yading@10: yading@10: /** yading@10: * @file yading@10: * MDCT/IMDCT transforms. yading@10: */ yading@10: yading@10: #if CONFIG_FFT_FLOAT yading@10: # define RSCALE(x) (x) yading@10: #else yading@10: # define RSCALE(x) ((x) >> 1) yading@10: #endif yading@10: yading@10: /** yading@10: * init MDCT or IMDCT computation. yading@10: */ yading@10: av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale) yading@10: { yading@10: int n, n4, i; yading@10: double alpha, theta; yading@10: int tstep; yading@10: yading@10: memset(s, 0, sizeof(*s)); yading@10: n = 1 << nbits; yading@10: s->mdct_bits = nbits; yading@10: s->mdct_size = n; yading@10: n4 = n >> 2; yading@10: s->mdct_permutation = FF_MDCT_PERM_NONE; yading@10: yading@10: if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0) yading@10: goto fail; yading@10: yading@10: s->tcos = av_malloc(n/2 * sizeof(FFTSample)); yading@10: if (!s->tcos) yading@10: goto fail; yading@10: yading@10: switch (s->mdct_permutation) { yading@10: case FF_MDCT_PERM_NONE: yading@10: s->tsin = s->tcos + n4; yading@10: tstep = 1; yading@10: break; yading@10: case FF_MDCT_PERM_INTERLEAVE: yading@10: s->tsin = s->tcos + 1; yading@10: tstep = 2; yading@10: break; yading@10: default: yading@10: goto fail; yading@10: } yading@10: yading@10: theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); yading@10: scale = sqrt(fabs(scale)); yading@10: for(i=0;itcos[i*tstep] = FIX15(-cos(alpha) * scale); yading@10: s->tsin[i*tstep] = FIX15(-sin(alpha) * scale); yading@10: } yading@10: return 0; yading@10: fail: yading@10: ff_mdct_end(s); yading@10: return -1; yading@10: } yading@10: yading@10: /** yading@10: * Compute the middle half of the inverse MDCT of size N = 2^nbits, yading@10: * thus excluding the parts that can be derived by symmetry yading@10: * @param output N/2 samples yading@10: * @param input N/2 samples yading@10: */ yading@10: void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input) yading@10: { yading@10: int k, n8, n4, n2, n, j; yading@10: const uint16_t *revtab = s->revtab; yading@10: const FFTSample *tcos = s->tcos; yading@10: const FFTSample *tsin = s->tsin; yading@10: const FFTSample *in1, *in2; yading@10: FFTComplex *z = (FFTComplex *)output; yading@10: yading@10: n = 1 << s->mdct_bits; yading@10: n2 = n >> 1; yading@10: n4 = n >> 2; yading@10: n8 = n >> 3; yading@10: yading@10: /* pre rotation */ yading@10: in1 = input; yading@10: in2 = input + n2 - 1; yading@10: for(k = 0; k < n4; k++) { yading@10: j=revtab[k]; yading@10: CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]); yading@10: in1 += 2; yading@10: in2 -= 2; yading@10: } yading@10: s->fft_calc(s, z); yading@10: yading@10: /* post rotation + reordering */ yading@10: for(k = 0; k < n8; k++) { yading@10: FFTSample r0, i0, r1, i1; yading@10: CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); yading@10: CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); yading@10: z[n8-k-1].re = r0; yading@10: z[n8-k-1].im = i0; yading@10: z[n8+k ].re = r1; yading@10: z[n8+k ].im = i1; yading@10: } yading@10: } yading@10: yading@10: /** yading@10: * Compute inverse MDCT of size N = 2^nbits yading@10: * @param output N samples yading@10: * @param input N/2 samples yading@10: */ yading@10: void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input) yading@10: { yading@10: int k; yading@10: int n = 1 << s->mdct_bits; yading@10: int n2 = n >> 1; yading@10: int n4 = n >> 2; yading@10: yading@10: ff_imdct_half_c(s, output+n4, input); yading@10: yading@10: for(k = 0; k < n4; k++) { yading@10: output[k] = -output[n2-k-1]; yading@10: output[n-k-1] = output[n2+k]; yading@10: } yading@10: } yading@10: yading@10: /** yading@10: * Compute MDCT of size N = 2^nbits yading@10: * @param input N samples yading@10: * @param out N/2 samples yading@10: */ yading@10: void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input) yading@10: { yading@10: int i, j, n, n8, n4, n2, n3; yading@10: FFTDouble re, im; yading@10: const uint16_t *revtab = s->revtab; yading@10: const FFTSample *tcos = s->tcos; yading@10: const FFTSample *tsin = s->tsin; yading@10: FFTComplex *x = (FFTComplex *)out; yading@10: yading@10: n = 1 << s->mdct_bits; yading@10: n2 = n >> 1; yading@10: n4 = n >> 2; yading@10: n8 = n >> 3; yading@10: n3 = 3 * n4; yading@10: yading@10: /* pre rotation */ yading@10: for(i=0;ifft_calc(s, x); yading@10: yading@10: /* post rotation */ yading@10: for(i=0;itcos); yading@10: ff_fft_end(s); yading@10: }