s->rdft = s->irdft = NULL;
s->rdft = av_rdft_init(av_log2(work_len), DFT_R2C);
s->irdft = av_rdft_init(av_log2(work_len), IDFT_C2R);
s->rdft = s->irdft = NULL;
s->rdft = av_rdft_init(av_log2(work_len), DFT_R2C);
s->irdft = av_rdft_init(av_log2(work_len), IDFT_C2R);