av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale) { int n, n4, i; double alpha, theta; int tstep; memset(s, 0, sizeof(*s)); n = 1 << nbits; s->mdct_bits = nbits; s->mdct_size = n; n4 = n >> 2; s->permutation = FF_MDCT_PERM_NONE; if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0) goto fail; s->tcos = av_malloc(n/2 * sizeof(FFTSample)); if (!s->tcos) goto fail; switch (s->permutation) { case FF_MDCT_PERM_NONE: s->tsin = s->tcos + n4; tstep = 1; break; case FF_MDCT_PERM_INTERLEAVE: s->tsin = s->tcos + 1; tstep = 2; break; default: goto fail; } theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); scale = sqrt(fabs(scale)); for(i=0;i<n4;i++) { alpha = 2 * M_PI * (i + theta) / n; s->tcos[i*tstep] = -cos(alpha) * scale; s->tsin[i*tstep] = -sin(alpha) * scale; } return 0; fail: ff_mdct_end(s); return -1; }