IRDFT            1903 libavcodec/qdm2.c     ff_rdft_init(&s->rdft_ctx, s->fft_order, IRDFT);
IRDFT              55 libavcodec/rdft.c     s->inverse         = trans == IRDFT || trans == IRIDFT;
IRDFT              61 libavcodec/rdft.c     if (ff_fft_init(&s->fft, nbits-1, trans == IRDFT || trans == RIDFT) < 0)