Re: [Discuss-gnuradio] gr.fft_vcc usage in make_fft_sink_X

[James Cooley]

I wasn't sure of the difference either... Except that I know that with 
the separate_streams/combine_streams, I had to dynamically create the 
number of IN/OUT streams depending on the fft size.  (Note, maybe 
sync_decimator handles the num in/out streams implicitly?)

Parallelize looks to me like it is designed to take a single stream, 
like this:
=================================================================

gr_serial_to_parallel::gr_serial_to_parallel (size_t item_size, size_t 
nitems_per_block)
 : gr_sync_decimator ("serial_to_parallel",
                      gr_make_io_signature (1, 1, item_size),
                      gr_make_io_signature (1, 1, item_size * 
nitems_per_block),
                      nitems_per_block)
{
}



Whereas, I had to do this:
================================================================
gr_separate_streams_ff::gr_separate_streams_ff (int num_streams)
 : gr_sync_block ("separate_streams_ff",
                  gr_make_io_signature (MIN_IN, MAX_IN, num_streams * 
sizeof (float)),
                  gr_make_io_signature (num_streams, num_streams, 
sizeof (float))),
   d_num_streams(num_streams)
{
}


gr_combine_streams_ff::gr_combine_streams_ff (int num_streams)
 : gr_sync_block ("combine_streams_ff",
                  gr_make_io_signature (num_streams, num_streams, 
sizeof (float)),
                  gr_make_io_signature (MIN_OUT, MAX_OUT, num_streams * 
sizeof (float))),
   d_num_streams(num_streams)
{
}









cswiger wrote:

> Are there any illustrative examples of using ifft? I just discovered
> the 2nd argument in gr.fft_vcc can set direction forward (True) or
> reverse, which is cool as I want ifft for some kind of simple OFDM.
> I guess what I don't understand is how gr.serial_to_parallel works. Do
> you use serial_to_parallal(type N) and suddenly end up with N data
> paths? gr.keep_one_in_n seems self explanatory.
>
> Also looking at James' gr_seperate_streams and gr_combine_streams re:
> fft processing.
>
> TIA
>
> --Chuck
>
>
>
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