[Discuss-gnuradio] How does ofdm sync work

[bin zan]

Hi,
       Does any one know how does ofdm in gnuradio do sync? 
       What I found in the gr_ofdm_frame_sink.cc is just check sig[0], which is just the second bytes of  input_items.  However, I didn't see any reason that the (const char *) input_items[1] will be NULL.

Thanks,
Bin Zan