SRT (Secure Reliable Transport)
Overview
SRT (Secure Reliable Transport) is a modern video transport protocol designed for low-latency, secure, and reliable streaming over unpredictable networks.
In ITVDesk, SRT is intended for public Internet and long-distance streaming scenarios where traditional RTSP/RTP streaming becomes unreliable.
SRT is not part of ONVIF and is not used for LAN-based camera discovery or integration.
Why SRT Exists
Streaming video over the public Internet introduces challenges such as:
- Packet loss due to network congestion
- Jitter and unstable packet arrival
- Bandwidth fluctuations
- Increased latency with TCP-based protocols
Traditional protocols have limitations:
- RTMP (TCP) offers reliability but high latency
- Raw UDP offers low latency but no reliability
- RTSP/RTP works well on LAN but degrades over WAN
SRT was designed to bridge this gap.
How SRT Works
SRT is built on UDP and adds intelligent recovery and control mechanisms:
UDP-Based Transport
- Avoids TCP head-of-line blocking
- Enables low-latency delivery
Adaptive Packet Recovery
- Uses ARQ (Automatic Repeat reQuest)
- Optionally uses FEC (Forward Error Correction)
- Recovers packet loss without large latency spikes
Dynamic Congestion Control
- Continuously adapts bitrate to network conditions
- Prevents congestion while maximizing quality
Stream Encryption
- Supports AES-128 and AES-256 encryption
- Protects content over public networks
SRT vs Other Protocols
| Protocol | Latency | Reliability | Best Use Case |
|---|---|---|---|
| RTSP / RTP | Low (LAN) | Medium | Local networks |
| RTMP | High | High | Legacy CDN workflows |
| Raw UDP | Very Low | None | Controlled networks |
| SRT | Low (WAN) | High | Public Internet streaming |
When to Use SRT in ITVDesk
Use SRT when:
- Streaming over the public Internet
- Network conditions are unstable
- Low latency is required
- Secure transmission is mandatory
Typical use cases:
- Remote contribution
- Inter-site video transport
- Cloud ingestion
- Secure long-distance monitoring
When NOT to Use SRT
Avoid SRT when:
- Using ONVIF discovery or control
- Streaming inside a local LAN
- Multicast distribution is required
- One-to-many broadcast is needed
SRT is designed for point-to-point (one-to-one) connections.
Security Notes
- SRT provides built-in encryption
- No TLS certificates are required
- Encryption keys are configured per connection
Summary
SRT in ITVDesk provides:
- Reliable Internet-grade video transport
- Low latency over unstable networks
- Built-in encryption
- Professional-grade WAN streaming
SRT complements RTSP/RTP but does not replace ONVIF-based workflows.