Squeezelite and spdif / sound frequently interrupted

[matrzh]

Hi,

I have just changed from a custom legacy kernel to armbian and like the experience.

I use the Logitech Media Server and squeezelite, mainly to play radio on the armbian box itself as well as on a Squeezebox Radio I still have.

This works in principle, but using the spdif optical output, I get an interrupt every minute or so of about half a second.

Is this common and do I need to install something in addition to use the spdif output?

 

System information:

• Allwinner A20 cubietruck
• Kernel (uname -r): 4.19.62-sunxi

• Squeezelite v1.8

• Logitech Media Server Version: 7.9.2 - 1565967976 @ Fri Aug 16 17:18:03 CEST 2019

• output of aplay -l

**** List of PLAYBACK Hardware Devices ****
card 0: sun4icodec [sun4i-codec], device 0: CDC PCM Codec-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: SPDIF [On-board SPDIF], device 0: spdif-dit-hifi dit-hifi-0 []
  Subdevices: 0/1
  Subdevice #0: subdevice #0

• output of squeezelite -l

Output devices:
  null                           - Discard all samples (playback) or generate zero samples (capture)
  default:CARD=sun4icodec        - sun4i-codec,  - Default Audio Device
  sysdefault:CARD=sun4icodec     - sun4i-codec,  - Default Audio Device
  dmix:CARD=sun4icodec,DEV=0     - sun4i-codec,  - Direct sample mixing device
  dsnoop:CARD=sun4icodec,DEV=0   - sun4i-codec,  - Direct sample snooping device
  hw:CARD=sun4icodec,DEV=0       - sun4i-codec,  - Direct hardware device without any conversions
  plughw:CARD=sun4icodec,DEV=0   - sun4i-codec,  - Hardware device with all software conversions
  default:CARD=SPDIF             - On-board SPDIF,  - Default Audio Device
  sysdefault:CARD=SPDIF          - On-board SPDIF,  - Default Audio Device
  dmix:CARD=SPDIF,DEV=0          - On-board SPDIF,  - Direct sample mixing device
  dsnoop:CARD=SPDIF,DEV=0        - On-board SPDIF,  - Direct sample snooping device
  hw:CARD=SPDIF,DEV=0            - On-board SPDIF,  - Direct hardware device without any conversions
  plughw:CARD=SPDIF,DEV=0        - On-board SPDIF,  - Hardware device with all software conversions

 

I run squeezlite with option -o hw:1

other options I tried was -o default:CARD=SPDIF, -o hw:CARD=SPDIF,DEV=0, plughw:CARD=SPDIF,DEV=0

The default option was the worst in terms of interrupts, I think.

 

Any hints?  Cannot see anything suspicious in the logs.  The interrupts do not appear if I use the hw:0 (sun4icodec), but the volume level and noise is much better with the spdif.

I read somewhere that it is normally not necessary to mess with buffer or alsa parameters. (-b / -a options in squeezelite)

 

[matrzh]

I am answering my own question.

I finally did play with the -a and -b options of squeezelite, and it seems that the option -a 400 does the trick, which is 400ms seconds of alsa buffer time, if I read the man page correctly.

I have been listening to squeezelite for the last 10 minutes or so and did not have an interruption, so far.

specifying a stream buffer with -b does not change anything (or only very marginally).

So for me:

To make squeezelite work well with spdif on a cubietruck (Allwinner A20 processor), I need to launch it as follows

squeezelite -o hw:1 -a 400

To properly load it with systemd, the following lines need to be in /etc/default/squeezelite :
 

SL_SOUNDCARD="hw:1" 
SB_EXTRA_ARGS="-a 400"

Maybe it helps someone