Long Audio Delay
Q: I have modular PA system, with an Audio Source Pack linked to one or more remote Output Packs via wireless Link Kits. I hear a noticeable delay between when I speak into the mic (or play a CD or Siren) and when I hear the sound come out of the Output Packs. How do I fix this?
A: You have too high a value entered into the “Play Buffer” field on the Settings Page of the Link Kit attached to your Output Packs. The play buffer stores a ‘reserve’ of data so that if the network connection gets interrupted, the audio you are streaming will not stop. The larger the play buffer is, the more interruptions in the network your system can handle without audible stuttering or silences. On the other hand, a large play buffer will cause an audible delay between when you send audio from the Audio Source Pack and when you hear that audio from the Output Pack.
To change the Play Buffer, log into the IP address of the Encoder part of the Link Kit attached to the Output Pack by entering the IP Address printed on the 1U Encoder Box into your Web Browser. Note that you can either directly connect a computer to the Ethernet Jack on the Encoder itself, OR remotely connect to the encoder from a remote network location that is on the same network. The Encoder generally has an IP address ending in .2, i.e. 192.168.27.2. For more information, see the Modular PA manuals in the Documents. Once you’ve accessed the correct Encoder’s web interface, select the “Settings” tab and enter the password tmset. Next, enter a lower or higher value in the Play Buffer field – a lower number will reduce the playback delay, and a higher value will create a ‘harder to kill’ playback behavior at the cost of a longer audio delay. Save the settings – the Output Pack Link Kit Encoder will reboot, and you’ll notice the change in play buffer behavior.
Note that while the SENDING Encoder – the one installed in the Audio Source Pack or other ‘transmitting’ device – has a Play Buffer, this has no effect EXCEPT if and when that device receives audio. Since Audio Source Packs normally send audio only, changing the Play Buffer of the A.S.P. will not make a difference in your system behavior. In other words, to reduce the audio delay in your system, reduce the play buffer settings for each Link Kit Encoder installed in an Output Pack or MilPA System.
Note also that you should keep all the Play Buffers in your multi-PA system set the same – this will keep the audio ‘in sync’ throughout your facility. If one Play Buffer is set to a lower value than another Output Pack’s Encoder’s play buffer, you’ll notice the audio stream playing with different amounts of delay at each Output Pack – not good, in most cases!