ON Comms specification
November 2026oncommstalkback.comsupport@oncommstalkback.com
Audio
- Codec
- Opus, 48 kHz mono, capped at 32 kbit/s
- Quiet lines
- DTX: a line nobody is talking on sends 3.2 kbit/s
- Lost packets
- RED: each packet also carries the frame before it
- On the wire
- 92.5 kbit/s up per line talked on; 89.2 kbit/s down per person heard (measured)
- Processing
- Echo cancelling, noise suppression and gain control; off for a wired headset in the browser and desktop apps
Transport
- Media
- WebRTC through a forwarding server that never decodes or mixes
- Cloud site
- Audio on UDP 7882; TCP 7881 where UDP is blocked; a TURN relay on UDP 3478; pages and signalling on HTTPS (443)
- ON Comms Server
- One port, TCP and UDP: 26670 by default
Latency
- Mouth to ear
- About 140–330 ms on 4G or 5G; about 60–120 ms on a venue network (budget)
- The server
- 1–5 ms
- Receive buffer
- About 20 ms on a quiet venue network (measured); adapts, or set by hand
- Readout
- Every panel shows its own buffer, round trip and cipher, live
Security
- Audio
- SRTP with AES-256-GCM, keys over DTLS; AES-128 for a device without GCM, shown in amber
- Cloud sites
- HTTPS throughout; a database and signing secret per customer; nightly backups sealed with AES-256-GCM
- Accounts
- bcrypt password hashes; one device per person; saved setups sealed with scrypt and AES-256-GCM
- Recording
- None: audio is never written to disk
Crew apps
- iPhone
- iOS 16.4 or later, with an Apple Watch key (watchOS 10 or later), from the App Store
- Android
- Android 7.0 or later
- Desktop
- The client for Mac (macOS 13 or later, from the Mac App Store) and Windows (64-bit)
- Browser
- Chrome and Edge; Safari on a Mac
Servers
- Cloud
- A site of your own at yourname.oncommstalkback.com
- ON Comms Server
- macOS 13.5 or later (Apple silicon or Intel); 64-bit Windows 10 (1809 or later) or Windows 11
- Licence
- Cloud: by the week, the month or for good. Server: a key, checked weekly, 30 days offline
Camera Tally
- Switchers
- Blackmagic ATEM (UDP 9910, the M/E you choose); vMix (TCP 8099)
- TSL UMD
- 3.1, 4.0 and 5.0, over UDP and TCP; listens on 40001 by default and never sends
- Cloud sites
- ON Comms Tally for Mac (macOS 13.5 or later) and Windows (64-bit)
Audio in and out
- Per line
- A device, then a pair or a channel, each way, with gain in dB
- Devices
- Core Audio on a Mac (Dante Virtual Soundcard included); WASAPI on Windows. Not yet: ASIO
- Cloud sites
- ON Comms Bridge for Mac (macOS 13.5 or later) and Windows (10 version 1809 or later, 64-bit)
Lines and control
- Lines
- As many per group as the show needs; talk, listen or nothing per person, changed live
- Priority
- Ducks the other lines by 6, 12 or 20 dB, or to silence
- Calls
- Private calls with reply keys; mic test lines on cloud sites
- Keys
- Stream Deck through Bitfocus Companion (HTTP); keyboard 1–9 and Space; Apple Watch