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

From: James Cooley
Subject: Re: [Discuss-gnuradio] gr.fft_vcc usage in make_fft_sink_X
Date: Wed, 16 Mar 2005 15:40:41 -0500
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

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),

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))),

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))),

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.



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