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[Discuss-gnuradio] How to deal with discrepancy in sample rate? (44.1Hz

From: Jonathan Coveney
Subject: [Discuss-gnuradio] How to deal with discrepancy in sample rate? (44.1Hz from a wavform, etc)
Date: Tue, 11 Aug 2009 22:52:38 -0400

Ok, so my goal is to be able to use a wav file and then fm modulate it, and store the result in a .dat file containing complex samples that could then be demodulated by an fm demodulator I have. But I'm running into a couple of problems!

Usually, the iconic sample rate seems to be 320KHz, and an audio_sink usually is set to 32KHz. However, the wavfile_source block has a sample_rate() attribute, and its about 44100. I didn't think that this would matter, except that when calling the fm modulator
fmtx = blks2.nbfm_tx (audio_sample, file_sample, max_dev=5e3, tau=75e-6)
it seems I have to set the sample rate (file_sample) equal to an integer multiple of the audio_sample rate...this makes intuitive sense, but it won't let me go as large as I want? At 10*audio_sample (when audio_sample is 44100), I get an insufficient extremals error... but if the audio sample rate is 32000, I can set the sample rate arbitrarily high!

Related to this is the question of demodulation. Usually, you want to be symmetric in your sample rates and all that...but given I'll be demodulating this signal via FM and probably going to a audio_sink (which has a sample rate of 32000? or can I also instantiate it with a sample rate that is higher?) I'm not sure how I can deal with the discrepancy between the two.

Your help is greatly appreciate!

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