audio underrun?

W5UXH

Just wondering if the underruns are anything that I can / should address somehow?  These seem to only show up in the browser log tab, not the "ms" list displayed at the Beagle ssh terminal connection.  They seem to show up on some of the connections but not on others that are also connected at the same time.

Tue Jan  3 20:17:31 2017 6d:01:57:09 01..      SND0: audio underrun 40 ::ffff:216.189.202.129 -------------------------
Tue Jan  3 20:17:31 2017 6d:01:57:09 01..      SND0: audio underrun 41 ::ffff:216.189.202.129 -------------------------
Tue Jan  3 20:17:33 2017 6d:01:57:11 01..      SND0: audio underrun 42 ::ffff:216.189.202.129 -------------------------
Tue Jan  3 20:20:39 2017 6d:02:00:17 01..      SND0: audio underrun 43 ::ffff:216.189.202.129 -------------------------
Tue Jan  3 20:20:39 2017 6d:02:00:17 01..      SND0: audio underrun 44 ::ffff:216.189.202.129 -------------------------
Tue Jan  3 20:20:40 2017 6d:02:00:18 01..      SND0: audio underrun 45 ::ffff:216.189.202.129 -------------------------

jks

Occasional under-runs like this are not unusual and not a problem. There are many sources of problems causing network traffic to be stalled. It doesn't matter for the waterfall but of course has bad consequences for the audio.

One of the factors that can't be controlled is Linux / Debian on the Beagle behaving badly. Although Linux generally is pretty good about process scheduling occasionally something happens which keeps the Kiwi server from running often enough. Due to the various resource constraints of FPGA buffering, SPI link speed etc. the Kiwi software must wakeup on average every 9 milliseconds. And buffer overflow leading to audio under-run occurs if a single stall exceeding about 20 milliseconds occurs.

Many people have asked for a wider audio bandwidth but that contributes directly to this problem.