App_jack.c – Error – Failing To Write To Ringbuffer

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Hi all,

I have been successufully using JACK application within Asterisk. Yet I
am hearing quite some glitches in both input and output ends

I am using jack with an external sound card RME HAmmerfall DSP Mutliface
, but also tried the internal sound card, without a significant change.

What seems to have improved a bit the quality was to change the jack settings to larger periods to its maximum 4096. There no longer sudden burst of noise, but the audio still choppy and distorted. And Asterisk console prints the following message:

WARNING[1837][C-00000003]: app_jack.c:598 queue_voice_frame: Tried to write 3532 bytes to the ringbuffer, but only wrote 2279

where the “only wrote” value changes between 0, 2279, 2255

jack is running with the following setting:

jackd -d alsa -r 44100 -p 4096 -nperiod 3 -C hw:DSP -P hw:DSP -S

I am on Asterisk 14.4.0 on Debian Jessie (8.7).

The extension I am using:
exten => 1234,1,Answer()
same = n,JACK(i(system:playback_1),o(mpv:out_0));

Any ideas of what can be done to improve the audio quality when using JACK app?

Thanks a