[AG-TECH] Audio cutting out

[Andrew Patrick]

You need to determine if it is an audio problem or a packet problem. 
Often things that you would think are packet problems (e.g., packet 
loss, jitter, etc.) turn out to be audio problems.

A few things to try on the audio side:

- in the options menu of RAT, under the Audio category, make sure that 
Silence Suppression and everything else is OFF (not checked).

- make sure that the sampling rate (usually 16-kHz) is set the same on 
the sending and receiving end

- under the Transmission category, make sure that you have selected an 
encoding that is compatible with music.  The usual setting of Linear-16 
should be OK

- for music tests, you might want to try higher sampling rates, such as 
48 kHz, but make sure you set the sampling rate the same on both the 
sending and receiving RAT

- of course you should double-check all of you audio wires and 
connections between your computer and speakers



Jon Johansson wrote:

> 
> We are testing our new room node and are finding that the
> audio is cutting out sporadically, sometimes for a couple
> of seconds. We've seen this in meetings with other sites
> using different nodes and haven't been able to find a cause.
> "Packet loss" seems to be a reasonable guess at the problem
> and sometimes we can actually see some loss on Rat's
> Reception quality matrix, but many times there is no
> measurable sign of loss.
> 
> In the current situation I am running a venue on a
> server under my desk (running RH9). My desktop machine is
> running AG 2.1.2 on WinXP and has been stable for months and
> I've used for many meetings. I've connected to my venue
> server through a 100Mb/s network (actually they are
> directly connected to the same Gig switch but only the AG
> client has Gig ethernet, the venue server has a 100 Mb/s
> ethernet card). In order to get a continuous audio stream
> I'm running Winamp and I've wired the audio out to the
> mic input so that rat is sending a steady music signal
> to the venue.
> 
> The room node is on the same subnet and physically close,
> with a single gateway between my desktop and the node
> equipment. tracert and mtrace from my desktop machine
> give the following:
> 
> C:\Documents and Settings\jonj>tracert ag-audio
> 
> Tracing route to ag-audio.cns.ualberta.ca [129.128.8.205]
> over a maximum of 30 hops:
> 
>   1    <1 ms    <1 ms    <1 ms  ag-audio.cns.ualberta.ca [129.128.8.205]
> 
> Trace complete.
> 
> C:\Documents and Settings\jonj>winmtrace ag-audio 233.59.192.5
> Mtrace from 129.128.8.205 to 129.128.8.151 via group 233.59.192.5
> mtrace: Source & receiver appear to be directly connected
> Querying full reverse path...
>   0  tyr.cns.ualberta.ca (129.128.8.151)
>  -1  cnsgw.ucs.ualberta.ca (129.128.8.1)  PIM  thresh^ 0
>  -2  ag-audio.cns.ualberta.ca (129.128.8.205)
> Round trip time 0 ms; total ttl of 1 required.
> 
> Waiting to accumulate statistics...Results after 10 seconds:
> 
>   Source        Response Dest    Overall     Packet Statistics For Traffic
> From
> 129.128.8.205   224.0.1.32       Packet      129.128.8.205 To 233.59.192.5
>      v       __/  rtt    0 ms     Rate       Lost/Sent = Pct  Rate
> 129.128.8.1     cnsgw.ucs.ualberta.ca
>      v      \__   ttl    2         0 pps        ?/0            0 pps
> 129.128.8.151   129.128.8.151
>   Receiver      Query Source
> 
> 
> Our network is quite robust and in trying to create additional loss
> we started several simultaneous large data transfers, without
> affecting the rat audio output noticably.
> 
> I don't know where else to look for problems without starting
> to dissect RAT itself. Would anyone have suggestions?
> 
> Thanks,
> Jon.
> 
> -- 
> Jon I Johansson             *  Research Computing Support
> jon.johansson at ualberta.ca   *  Computing and Network Services
> Tel.: (780) 492-9304        *  University of Alberta
> Fax.: (780) 492-1729        *  Edmonton, Alberta, CANADA
>  
> 

-- 
Andrew Patrick, Ph.D.
Senior Scientist
Information Security Group, Institute for Information Technology
National Research Council (NRC), Ottawa, Canada
E-mail: Andrew.Patrick at nrc-cnrc.gc.ca
WWW - NRC:  http://iit-iti.nrc-cnrc.gc.ca
WWW - Personal: http://www.andrewpatrick.ca
Phone: (613) 991-3374   Fax: (613) 952-7151  Cell: (613) 277-9211