Vibration like sound on audio

AllStarLink
1

Having an issue with multiple nodes experiencing a vibrato/fast stuttering effect on certain user’s syllables.

It seems to be random. More noticeable on some voices than others. Seems like it affects female voices more than male voices. It only lasts for about 100-200ms. It can happen at the beginning of a transmission, or 60 seconds into a transmission. Almost like a buffer of some sort is playing catch up.

Link paths are stable and have plenty of bandwidth. Most sites are on cable modems or enterprise networks. Latency and jitter look good via the CLI iax2 show channels command.

Audio levels on all nodes are aligned properly using an Aeroflex service monitor and the SimpleUSB tools. Running the latest updates, and all nodes are running on Raspberry Pi 5 4gb boards.

I tried playing with the jitter buffer settings in SimpleUSB, but it did not seem to make any difference.

If I restrict the RADIO vocoder selection in iax.conf to allow only G762aal2, it is almost non-existent. However, it is quite noticeable when using ULAW or SLIN. I prefer to use ULAW at a minimum, with SLIN being the primary choice.

Any suggestions?

Eric

K2CB

Setup Information

********** AllStarLink [ASL] Version Info **********

OS : Debian GNU/Linux 12 (bookworm)
OS Kernel : 6.1.0-40-amd64

Asterisk : 22.4.1+asl3-3.5.5-1.deb12
ASL [app_rpt] : 3.5.5

Installed ASL packages :

Package Version
============================== ==============================
allmon3 1.6.0-3.deb12
asl3 3.9-1.deb12
asl3-asterisk 2:22.4.1+asl3-3.5.5-1.deb12
asl3-asterisk-config 2:22.4.1+asl3-3.5.5-1.deb12
asl3-asterisk-modules 2:22.4.1+asl3-3.5.5-1.deb12
asl3-menu 1.14-1.deb12
asl3-update-nodelist 1.5.1-1.deb12
cockpit 337-1~bpo12+1
cockpit-bridge 337-1~bpo12+1
cockpit-networkmanager 337-1~bpo12+1
cockpit-packagekit 337-1~bpo12+1
cockpit-storaged 337-1~bpo12+1
cockpit-system 337-1~bpo12+1
cockpit-ws 337-1~bpo12+1
dahdi 1:3.1.0-2
dahdi-dkms 1:3.4.0-8.asl.deb12
dahdi-linux 1:3.4.0-8.asl.deb12

2

Transmit or receive audio? What interface?

3

On incoming (receive audio into the soundcard board) from other nodes.

Using the Masters Communications RL-20M at two sites, the RL-33M at two sites, and a few of the Repeater-Builder RIM-Lite Scom and RLC boards at other sites.

I hear it occur on system users originating on either the Master or RB board based sites.

Eric

K2CB

4

If anyone would like to hear it, please feel free to connect to my hub node 616530.

Eric

K2CB

5

Does it kind of sound like a burst fire from an automatic weapon?

6

Yes it does, even though it's only about 200 milliseconds at best.

7

Interesting, I have been noticing this sound on my local ASL3 repeater for a few weeks.

8

For what it is worth, I was doing some experimenting with usbradio versus simpleusb, for other reasons. It appeared as if this machine-gun vibration like effect that I occasionally hear on some users was absent while running usbradio. I will have to experiment and listen some more.

Eric
K2CB

9

After some observation, I am noticing an awful lot of this from ASL3 nodes, specifically, both usbradio and simpleusb.

What seems to be happening, just listening by ear, is that, every few seconds, half of every frame (assuming each frame is 20 ms) goes missing, which creates a 50 hz modulation/scraping/stair stepping effect. It comes and goes in cycles. It might be completely solid for, say, about five seconds, then it scrapes for a second, it’s fine for another five seconds, etc. If a test tone is injected into the node’s RX, it’s very noticeable that it is no longer a completely smooth sine wave.

I can make an extreme example of this sound by generating 10 milliseconds of white noise in my DAW, followed by 10 milliseconds of silence, then looping it forever.

I am monitoring nodes with a device that is not affected in such a way, so when it happens, it’s very clear that the node on the other end is ASL3 using one of the two channel drivers.

It doesn’t matter if the ASL3 node in question is running on a Raspberry Pi or some other device.

Not all ASL3 nodes do it, but lots of them do, including some that I know for a fact are ClearNodes.

This doesn’t happen with RTCM, by the way. Only the two USB channels.

If anyone is looking for concrete examples, I can probably make recordings available. I don’t currently have a local ASL3 node with a sound fob attached for testing purposes, but I can change that soon.

10

A recording would be splendid, so we can all be sure that we are talking about / describing the same issue.

11

I have tried switching from SimpleUSB to USBRadio. It occurs using either one.

I have tried using various codes. SLIN, ULAW, G726..... It occurs using any of them.

My latency on the links looks fairly good. Not sure what to try next.

12

To your point, Patrick, I have taken one of my nodes and connected to a few large systems out in WA and IL, and can listen to them for hours, and never hear it occur. I noticed that those nodes were negotiating using G726, so I am wondering if they are using older HamVoip nodes. Maybe that's why I do not hear it when connecting to these other systems.

13

I have a bunch of HamVoIP nodes still, which all negotiate either with slin or ulaw (usually slin) and they definitely have never done that. So, yeah, could be, since HamVoIP likes to default to G726.

FWIW, I just today set up an ASL3 node for a friend using a Raspberry Pi 3 mmodel B Plus, usbradio (DSP) and a DINAH connected to a Kenwood TM-V71A, and it, so far, hasn’t exhibited this behavior at all.