IDFT_R2C          105 libavcodec/rdft.c     s->sign_convention = trans == IDFT_R2C || trans == DFT_C2R ? 1 : -1;
IDFT_R2C          110 libavcodec/rdft.c     if (ff_fft_init(&s->fft, nbits-1, trans == IDFT_C2R || trans == IDFT_R2C) < 0)