Audio underruns

[Barry Duggan]

Ubuntu 20.04.1
GRC 3.9.0.0-git
The 
https://github.com/gnuradio/gnuradio/blob/master/gr-analog/examples/USRP_FM_stereo.grc 
flowgraph works properly with the device name blank.

With a copy of that file, I replaced the "WBFM Receive PLL" block with a 
"WBFM Receive" block (the monophonic version).

The mono FM audio is terribly distorted and has lots of audio underruns 
when the device name is blank, but works well with a device name of 
"hw:CARD=Generic,DEV=0".

This does not make any sense to me. How can changing the ALSA device 
name affect the audio underruns? Or, how does changing the demodulator 
require changing the ALSA device name?

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Barry Duggan KV4FV
https://github.com/duggabe