Forum: GNU Radio Reducing the samples from ADC

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58e69d83ac8ac33ae500e6220298fcaa?d=identicon&s=25 pratik hetamsaria (Guest)
on 2007-07-11 18:10
(Received via mailing list)
i am working on and I have to capture data
directly from usrp and write onto a file and process that. The problem
is that the file which is made by the data coming from usrp is very big
so basically i am not able to process that. Is there any way by which i
can reduce the size of the file without affecting my audio quality much.

The rates which i am presently using on the are:
Bitrate- 50,000
samples per symbol - 5
interpolation - 512

Rates which i am using on the are:
Bitrate- 50,000
 samples per symbol - 5
decimation - 256.

Moreover, i have tried using gr.fir_filter_ccf (for decimatio in
software)in the following fashion

        chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
                                          self._samples_per_symbol, #
sampling rate
                                          1.0,                  #
midpoint of trans. band
                                          0.1,                  # width
of trans. band
                                          gr.firdes.WIN_HANN)   # filter

        self.chan_filt = gr.fir_filter_ccc(sw_decim, chan_coeffs)

and making a connection as
    fg.connect(self.u,  self.chan_filt, self.packet_receiver)

where destination refers to the file onto which i want to write.Now,
this works fine as long as sw_decim =1. But, if i change the value to
2,4 ,8 or any other then i dont receive any packet. The file size does
change as required (i am able to observe that as the usrp is always
sending data). what i have understood is that because of the decimation
i am missing samples and thus not able to receive packets.So, can
somebody please explain how to get around the situation.

Thanks for all the help.
Pratik Hetamsaria
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