Raspberri Pi > Pi audio link for broadcast comms

Asterisk Asterisk General
#1

Hello,

I work in television broadcast and we regularly use a variety of methods for 2 way communications between sites, however these can sometimes be quite pricey and inflexible.

I was wondering if asterisk would be the right tool to achieve the following:

Raspberry Pi in site A connected to Raspberry Pi in site B over a VPN. Each pi would be connected to a USB sound card with say 4 audio inputs and outputs. I’d like to have 4, two way connections going between the Pi’s. Ideally I’d like to be able to build a nice web interface or node red style thing to establish the connections. I feel like SIP would be the most obvious way of doing this, but am fairly new to this side of the industry.

Would anyone have any pointers of suggestions on how to get started?

I’ve had asterisk up and running with webRTC clients, but want something with less of a user interface and more just straight audio links.

Thanks in advance,
Dan

#2

Is this 4 independent conversations or is it 8 participants all in the same party line like a group edit or table read?

Will each participant be using a telephone or an audio (not telephony’ish) headset with a boom?

If independent conversations, does the configuration need to change or is it always A1/B1, A2/B2, etc.?

#3

What it is the final goal here ?

#4

So it would be 4 separate conversations, in the broadcast world it’s what we refer to as a 4-wire. So in this case, with the 4 inputs and output from the soundcard, it would be 4x4wires.

The inputs and outputs would tie into a seperate intercom system, so for example if you had a director in site A, they would have a button that talks to a director in site B and vice versa. When they press the button the audio would go into the sound card and come out at the other end.

The goal here is to essentially use Asterisk/SIP as an audio transport tool.

#5

I think the Jack() app could work for you

#6

Is Asterisk over-kill for this task?

Would something like this Octo HAT and a fixed application running on each Pi that copies audio frames from each channel, concatenates the frames into IP packets and sends it to the other Pi such that a frame read from A1 is written to B1, B1 to A1, A2 to B2, B2 to A2, etc. do the trick?

#7

As @sedwards imp;ies, Asterisk is likely to be an overkill for this. However, sometimes overkill solutions an be the easiest solutions, as they can involve less technical programming.

#8

Two edged sword :slight_smile:

That additional complexity could put you on the receiving end of a ‘Tom Cruise Covid Rant’ for stopping production and not being able to diagnose and resolve the issue in the field.

Production intercom systems can be complex and expensive ($x0,000):

https://videoengineer.net/pages/intercom_systems.htm
https://www.clearcom.com/choosing-the-right-wireless-intercom-system-2-wire-4-wire-interfacing-part-2-of-9/

There’s even a job title associated – ‘Intercom Configuration Specialist’ – who knew :slight_smile:

Of course, it all depends on the level of complexity the OP needs. Something that just powers up, searches for it’s mate, and establishes 4 fixed ‘circuits’ between matching ports on sound cards or is there more detail that needs to be revealed to make decisions?