SRT Configuration

Secure Reliable Transport (SRT) is an open-source protocol designed for low-latency, high-reliability video transport over unpredictable networks. It uses UDP with ARQ (Automatic Repeat Request) error correction and AES encryption, making it the protocol of choice for remote contribution and professional ingest workflows.

When to use SRT

SRT excels in scenarios where reliability and security are critical:

• Remote contribution — Sending camera feeds from on-location to a central production facility over the public internet
• Unreliable networks — Cellular, satellite, or congested public Wi-Fi where packet loss is expected
• Encrypted transport — Content that requires AES-128 or AES-256 encryption in transit
• Bonded connections — Combining multiple network interfaces for higher aggregate bandwidth

For sub-second latency in browser-based workflows, consider WebRTC instead. For maximum encoder compatibility with no latency requirements, RTMP remains the simplest option.

SRT connection modes

SRT supports two connection modes. The mode you choose depends on your network topology and firewall configuration.

{% tabs %} {% tab label=“Caller Mode (Recommended)” %} In caller mode, your encoder initiates the connection to the WAVE SRT listener. This is the most common configuration and works well when WAVE’s ingest endpoint has a public IP.

Encoder settings:

• Mode: Caller
• Host: Your WAVE SRT ingest URL (e.g. srt://ingest.wave.online)
• Port: 9000 (default) or the port shown in your stream settings
• Stream ID: Your WAVE stream key
• Latency: 200ms minimum (increase if you experience packet loss) {% /tab %}

{% tab label=“Listener Mode” %} In listener mode, your encoder listens on a port and WAVE connects to it. This is useful when the encoder is behind a firewall that cannot accept outbound SRT connections, but can accept inbound ones.

Encoder settings:

• Mode: Listener
• Port: Choose an available UDP port (e.g. 9000)
• Passphrase: Set to match your WAVE stream configuration

WAVE settings:

• Configure WAVE to connect as a caller to your encoder’s public IP and port via the dashboard under Stream Settings > Advanced > SRT Pull Mode. {% /tab %} {% /tabs %}

Encryption

SRT supports AES encryption to protect your stream content in transit. WAVE supports both AES-128 and AES-256.

{% callout type=“info” title=“Encryption is optional but recommended” %} While SRT works without encryption, we strongly recommend enabling it for any content sent over the public internet. The performance overhead of AES encryption is negligible on modern hardware. {% /callout %}

To enable encryption:

1. In your WAVE stream settings, navigate to Ingest > SRT > Encryption.
2. Choose AES-128 or AES-256 and enter a passphrase (10-79 characters).
3. Enter the same passphrase in your encoder’s SRT configuration.

{% callout type=“warning” title=“Passphrase mismatch” %} If the passphrase on your encoder does not match the WAVE stream configuration exactly, the SRT handshake will fail silently. Passphrases are case-sensitive and must match character for character. {% /callout %}

Latency tuning

The SRT latency parameter controls the size of the receive buffer. A higher value provides more time for retransmissions (better for lossy networks), while a lower value reduces end-to-end delay.

Network quality	Recommended latency	Use case
Excellent (wired LAN)	120-200ms	Studio-to-studio within the same facility
Good (stable broadband)	200-500ms	Home office to cloud
Fair (cellular/Wi-Fi)	500-1000ms	On-location mobile contribution
Poor (satellite, high loss)	1000-2000ms	Remote or hostile network environments

{% callout type=“tip” title=“Start high, tune down” %} Begin with a latency of 500ms and gradually reduce it while monitoring the packet recovery rate in the WAVE dashboard. If recovery exceeds 5%, increase the latency buffer. {% /callout %}

Bandwidth overhead

SRT’s ARQ mechanism adds bandwidth overhead proportional to network packet loss. Plan for approximately:

• 0% loss: ~2% overhead (protocol framing)
• 1% loss: ~5% overhead
• 5% loss: ~15-20% overhead
• 10% loss: ~30-40% overhead (consider increasing latency or switching networks)

Ensure your available upload bandwidth exceeds your stream bitrate plus the expected overhead for your network conditions.

Monitoring SRT connections

The WAVE dashboard provides real-time SRT connection metrics under Stream > Health > SRT Details:

• RTT (Round-Trip Time): Network latency between encoder and WAVE
• Packet Loss: Percentage of packets lost and recovered
• Retransmission Rate: How aggressively ARQ is recovering lost packets
• Available Bandwidth: Estimated bandwidth on the path
• Buffer Fill Level: How much of the latency buffer is in use

{% troubleshooter issue=“srt-handshake-timeout” /%}

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