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RTP Multicast Streaming

Overview​

RTP Multicast allows multiple RTSP clients to receive the same audio and video stream using a single multicast RTP transmission.

This significantly reduces:

  • CPU usage
  • Network bandwidth
  • Encoder load

RTP Multicast is especially useful when multiple viewers watch the same ITVDesk Virtual ONVIF IP Camera stream inside a local network (LAN).

Enable Stream Multicast ITVDesk

How RTP Multicast Works in ITVDesk​

When RTP multicast is enabled:

  • The RTSP server assigns a multicast IP address automatically
  • Multicast addresses are randomly selected from the 232.x.x.x range
  • The multicast address cannot be configured manually
  • The RTSP stream URL remains unchanged

Example RTSP URL (same as unicast):

rtsp://<ITVDESK_IP>:5554/ipc1-stream1/screenlive

Multicast Session Behavior​

RTP multicast sessions behave as follows:

  • The first RTSP client starts the encoder and transmits audio/video
  • Additional RTSP clients reuse the same multicast RTP stream
  • All clients receive data from the same multicast address
  • Only one encoder instance is active per stream

This design allows multiple viewers without duplicating encoding work.

Configuration​

To enable RTP multicast streaming, the multicast option must be enabled in ITVDesk Settings (Streaming Service Settings).

tip

RTP Multicast is a global RTSP server option and applies to all streams.

Once enabled:

  • New RTSP sessions may automatically use multicast
  • No special RTSP URL or parameter is required
  • Clients must support multicast reception
Enable Stream Multicast ITVDesk

RTSP Stream Address​

The RTP multicast stream uses the same RTSP URL as a standard unicast stream.

There is no separate multicast URL.

RTSP clients that support multicast will automatically join the multicast group when the stream is opened.

Client Compatibility​

To receive RTP multicast streams, the client must support:

  • RTP multicast
  • UDP transport
  • Multicast routing (IGMP)

Compatible clients typically include:

  • VLC Media Player
  • Professional VMS systems
  • ONVIF-compliant RTSP clients

Testing RTP Multicast​

RTP multicast playback can be tested using a multicast-capable RTSP client.

Open the stream using the standard RTSP URL. Use VLC to test RTP multicast with the following settings:

Enable Stream Multicast ITVDesk

Network Requirements​

RTP multicast requires:

  • Multicast-enabled switches and routers
  • Proper IGMP support
  • UDP traffic allowed on the network

⚠️ RTP multicast does not work across:

  • NAT boundaries
  • Public Internet connections
  • Networks without multicast routing

Limitations & Notes​

  • RTP multicast is intended for LAN environments
  • Not suitable for WAN or Internet streaming
  • Multicast IP addresses are assigned automatically
  • SRTP multicast is not supported
  • Firewalls must allow UDP multicast traffic
tip

When multiple NVR systems are connected to ITVDesk:

  • Unicast RTSP is recommended if more than one NVR records the same stream
  • Each NVR gets its own RTSP session with independent timing and control

RTP multicast is best suited for live viewing scenarios (video walls, monitoring stations, multiple viewers), not for multi-NVR recording setups.

Streaming Topology Overview​

Each NVR receives its own independent RTSP session.

          ┌──────────┐
          │ ITVDesk  │
          └────┬─────┘
               │ RTSP (Unicast)
        ┌──────┴──────┐
        │             │
┌───────▼───────┐ ┌───▼─────────┐
│    NVR #1     │ │   NVR #2    │
│  Recording    │ │  Recording  │
└───────────────┘ └─────────────┘
  • Independent timing
  • Independent reconnect
  • Reliable multi-NVR recording
  • Recommended for production use

RTP Multicast (Live Viewing Only)​

All clients receive the same shared RTP stream.

          ┌──────────┐
          │ ITVDesk  │
          └────┬─────┘
               │ RTP Multicast (232.x.x.x)
        ┌──────┴──────┐
        │             │
┌───────▼───────┐ ┌───▼─────────┐
│    NVR #1     │ │   NVR #2    │
│  Live View    │ │  Live View  │
└───────────────┘ └─────────────┘
  • Single encoder instance
  • Shared RTP stream
  • No per-client isolation
  • Not recommended for multi-NVR recording

Typical Use Cases​

  • Control rooms
  • Monitoring walls
  • Training environments
  • Multiple operators viewing the same live stream
  • Bandwidth-optimized LAN deployments

Summary​

RTP Multicast in ITVDesk provides:

  • Efficient multi-client streaming
  • Single encoder instance per stream
  • Reduced CPU and network usage
  • Transparent RTSP URL usage
  • Ideal LAN-based stream distribution

This feature is recommended when many viewers need the same live stream inside a controlled network environment.

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