Re: [Discuss-gnuradio] problems connecting wavfile_source to usrp_sink.

[Justin G. Eskesen]

Thank you Martin.

Knowing that there is no fundamental reason that this setup would not work, led me to investigate a different section of my code & I discovered that I was running with a usrp decimation too low for my system & a wav file with too high a sample rate.

As for the short int wav file, I'm writing this code so that a number of students, who don't use anything but matlab, will have access to the usrp board for their various experiments. I can cut out the FIR filter if I desire & require a compatible input wav file sampling rate... I was just trying to make it flexible to input wav files of varying sample rates.  I have a competing desire to make it efficient, as I my be running this on a 333 mHz PC-104 board.  So, its a tradeoff.

That said, it works beautifully now.  Thanks again.

Justin

On Fri, May 15, 2009 at 3:56 AM, Martin Braun <address@hidden> wrote:

On Wed, May 13, 2009 at 04:25:39PM -0400, Justin G. Eskesen wrote:
> P.S. I've tried both wavfile_source & file_source & neither work.  I'm aware of
> the -1.0 to 1.0 normalization in wavfile_* & have commented that portion of the
> code out.  If I get this to work, I'll write a wavfile_source & sink that do no
> rescaling & take shorts because I'm doing too many unecessary conversions.

For the start, it probably would have been better to put in a
gr.multiply_const_ff() after the filter with a value of something like
20000. In the setup you mentioned, reading shorts from the WAV file
would not have helped, since you're using a float FIR afterwards, and a
short FIR would introduce too much quantization noise.

I've tried pretty much exactly the same setup before (but with the
multiplier) and it worked. Also, for debugging, I recommend using a
file_sink (not a wavfile_sink) instead of the USRP and check the sample
values in that file scale well in the DAC range. Actually, if you /did/
pipe it to WAV or audio, it should /not/ work, since they rely on data
being between -1 and 1.

Should you do ever do write a short wavfile_* and also want to support 8
Bit, remember that scales differently.

Hope this was what you wanted.
MB


--
Dipl.-Ing. Martin Braun           Phone: +49-(0)721-608 3790
Institut fuer Nachrichtentechnik  Fax:   +49-(0)721-608 6071
Universitaet Karlsruhe (TH)       http://www.int.uni-karlsruhe.de/

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