
VMS | ONVIF | SIP | RTSP
CWT-400
SIP to ONVIF Bridge for VMS Users

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The CWT-400
SIP to ONVIF Bridge
If you need to stream audio to a VMS then the CWT-400 is the product you're looking for!
ONVIF
The ONVIF protocol was developed for the security industry in 2008 as a standard method to allow a wide range of security equipment such as video cameras to communicate with monitoring and recording equipment. The ONVIF standard is now supported by all leading security video camera and video management system (VMS) manufacturers. e.g. Milestone, IndigoVision, JSI 4Sight, etc.
SIP
By contrast, the broadcast and telephony industries have adopted Session Initiation Protocol (SIP) as the standard for audio, video and messaging. Nearly all digital telephones and professional broadcast audio systems use SIP which offers more functionality than ONVIF, particularly in its ability to provide communication between devices whose IP address is unknown to the distant party.
Aside from protocol constraints, users wishing to connect a SIP-enabled audio source to an ONVIF-compliant VMS are confronted by the fact that most VMS equipment assumes the audio equipment to be ‘always on’. This can be a problem because configuration of such equipment on a VMS often involves a discovery process in which the VMS looks for a streaming source, registers it and then assumes it to be permanently available. Furthermore, most examples of VMS equipment have no ability to initiate streaming from front-end devices which may be required to be switched off, for example to save power.
The CWT-400 solves these problems and allows front-end SIP-enabled devices to work with ONVIF-compliant video management systems.
The CWT-400 gets your audio through!
This unique soloution is the hassle-free way to send high quality audio from source to VMS with no fuss.
- Works with all major video management systems
- OPUS in - AAC out means maximum quality
- No intermediate trasncoding
- Simple to install
- Can work without static IP addresses
- Saves $$$ on cellular connections!
A Unique Solution!
The CWT-400 acts as a bridge between SIP-enabled audio devices ONVIF-compliant video management systems. The audio source see the CWT-400 as a SIP client and can call the bridge to start an audio stream, treating the CWT-400 as a codec. By contrast, the video management system will see the CWT-400 as an ONVIF-compliant video camera. The CWT-400 sends a plain video image to maintain the connection and at the same time sends the audio stream which is received by the VMS just as if the sound was coming from a video camera.
In the design of the CWT-400 emphasis has been placed on exceptional audio fidelity. It accepts Opus-encoded audio and converts this to AAC. These are the two highest quality compression standards in the broadcast and security industries respectively. The conversion between the two is direct - there is not intermediate transcoding.
The CWT-400 can be supplied in:
- Single-units in Raspberry Pi form-factor cases
- 2U rack-mountable frames of up to 10 devices
- In sets of 10 in a mobile, carry-on flightcase (special order)
The CWT-400 was developed entirely by our team in Europe.
FAQs
Can I send audio to the CWT-400 using a CODEC?
Yes, provided the codec you are using can communicate using SIP or can act as an RTP audio source then you can use it to send audio to the CWT-400.
Does the CWT-400 have an analogue audio interface?
Yes, the CWT-400 is fitted with a line level analogue output to enable the user to monitor the audio stream passing through it. In fact, you can use the CWT-400 as a SIP to analogue codec if you wish.
Is this a Raspberry Pi?
No, the CWT-400 shares no electronics with the Raspberry Pi and does not require knowledge of Linux to operate. But for convenience we designed the unit to have the same form-factor as the Raspberry Pi so you can use the same enclosures and power supplies as the Pi.
How do I configure the CWT-400?
The CWT-400 has a normal web user interface where the user can configure the SIP and ONVIF settings.
Does the CWT-400 support NAT traversal?
Yes, the CWT-400 is designed to allow users to make connections which cross through firewalls and it supports SIP, STUN, TURN and ICE.
Does the CWT-400 have a display?
The CWT-400 does not come with a display as standard but it has an interface which supports a small OLED screen. This makes it ideal for anyone wishing to put the CWT-400 in their own enclosure.
Do I need a SIP server?
Not necessarily - it depends how you want to configure your network. If your VMS or other ONVIF-compliant device is not on a static IP or you need to pass through a firewall then you might like to use a SIP server to act as a proxy. But if your SIP audio source is on the same network then a SIP server will not be required.
Do I need any special software
No, the CWT-400 is a self-contained device and is configured using a web browser.
Is it easy to set up?
Yes! Just add the CWT-400 to your VMS as an ONVIF device. Your audio device can now place a SIP call to the CWT-400 and start streaming. (Alternatively, the CWT-400 can stream from RTP sources using RTSP to establish the connection.)
Where can I buy one?
The CWT-400 is brand new and during the early part of 2021 is being provided exclusively to customers on our development program. However, if you'd like to be notified when it will go on general release please let us know.
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