audio sink RuntimeError: audio_oss_sink

[aardric]

Hail,

    I am introducing myself to SDR technology and gnuradio through 
whatever project documentation I find, dissecting the code and executing 
simple experimental flow graphs to test understanding of concepts, 
hoping to avoid forum queries (this is my first). Although the audio 
sink is not critical to my ultimate use of gnuradio and a bit of a 
diversion I will eventually start digging into it. However, I thought to 
submit a query on whether there is something obvious I should try in 
order to get it working. I am using gnu radio companion 3.8.1.0 (Python 
3.6.10) and feeding the audio sink with a 1 kHz tone from the signal 
source block.

(1) staring with:
:~> aplay -L
null
     Discard all samples (playback) or generate zero samples (capture)
default
     Default ALSA Output (currently PulseAudio Sound Server)
sysdefault:CARD=PCH
     HDA Intel PCH, ALC892 Analog
     Default Audio Device
front:CARD=PCH,DEV=0
     HDA Intel PCH, ALC892 Analog
     Front speakers
surround21:CARD=PCH,DEV=0
     HDA Intel PCH, ALC892 Analog
     2.1 Surround output to Front and Subwoofer speakers
(...)
hdmi:CARD=PCH,DEV=0
     HDA Intel PCH, HDMI 0
     HDMI Audio Output
hdmi:CARD=PCH,DEV=1
     HDA Intel PCH, HDMI 1
     HDMI Audio Output
hdmi:CARD=PCH,DEV=2
     HDA Intel PCH, HDMI 2
     HDMI Audio Output
hdmi:CARD=PCH,DEV=3
     HDA Intel PCH, HDMI 3
     HDMI Audio Output
hdmi:CARD=PCH,DEV=4
     HDA Intel PCH, HDMI 4
     HDMI Audio Output

(2) using sysdefault:CARD=PCH for the audio sink device name,
both 44.1 kS/s and 48 kS/s the following runtime error results:

(3)
gr::log :INFO: audio source - Audio sink arch: oss
audio_oss_sink: sysdefault:CARD=PCH: No such file or directory
Traceback (most recent call last):
   File "/gnuradio/examples/audiotest.py", line 136, in <module>
     main()
   File "/gnuradio/examples/audiotest.py", line 112, in main
     tb = top_block_cls()
   File "/gnuradio/examples/audiotest.py", line 78, in __init__
     self.audio_sink_0 = audio.sink(samp_rate, 'sysdefault:CARD=PCH', True)
   File 
"/usr/local/lib64/python3.6/site-packages/gnuradio/audio/audio_swig.py", 
line 220, in make
     return _audio_swig.sink_make(*args, **kwargs)
RuntimeError: audio_oss_sink

 >>> Done (return code 1)

(4) Fixing this isn't critical and in time I will get to the bottom of 
it; the forum query just removes the possibility of an obvious answer 
that most everyone else knows about. My guess is that I have to disable 
the Pulse audio server.


Rick