How to Setup OBS Studio SRT Stream with AES Encryption

This guide provides a straightforward, step-by-step walkthrough on how to configure OBS Studio to stream using the Secure Reliable Transport (SRT) protocol secured with Advanced Encryption Standard (AES) encryption. You will learn how to format the SRT connection URL, apply the correct encryption parameters, and configure OBS Studio’s stream settings for a secure, low-latency broadcast.

Step 1: Understand the SRT AES URL Syntax

OBS Studio supports SRT natively. To enable AES encryption, you do not use separate input fields for passwords; instead, you append the encryption parameters directly to the SRT destination URL in the query string.

The standard format for an encrypted SRT URL is: srt://[IP_Address]:[Port]?mode=caller&passphrase=[Your_Password]&pbkeylen=[Key_Length]

Key Parameters Explained:

• srt://[IP_Address]:[Port]: The IP address and port of your receiving server (e.g., srt://192.168.1.100:5000).
• mode=caller: Defines OBS as the sender initiating the connection.
• passphrase: The secret password used to encrypt the stream. This must be between 10 and 79 characters long.
• pbkeylen: The Crypto Key Length in bytes. This defines the AES encryption strength.
  • 16 = AES-128 (128-bit encryption)
  • 24 = AES-192 (192-bit encryption)
  • 32 = AES-256 (256-bit encryption)

Example URL using AES-256:
srt://stream.example.com:5000?mode=caller&passphrase=MySecurePassword123&pbkeylen=32

Step 2: Configure OBS Studio Stream Settings

Once you have formulated your SRT URL, apply it inside OBS Studio:

1. Open OBS Studio.
2. Click on Settings in the bottom-right control panel (or go to File > Settings).
3. Select the Stream tab from the left-hand menu.
4. In the Service dropdown menu, select Custom….
5. In the Server text field, paste your formatted SRT URL (e.g., srt://stream.example.com:5000?mode=caller&passphrase=MySecurePassword123&pbkeylen=32).
6. Leave the Stream Key field completely blank (unless your receiving server specifically requires a streamid parameter, which would also be appended to the Server URL as &streamid=your_stream_id).
7. Click Apply, then click OK.

Step 3: Configure Output Settings for SRT

SRT works best with hardware encoders and specific bitrate settings. For an optimal experience:

1. Go back to Settings and select the Output tab.
2. Set the Output Mode to Advanced.
3. Under the Streaming tab, select your encoder (e.g., NVIDIA NVENC H.264 or AMD HW H.264).
4. Set the Rate Control to CBR (Constant Bitrate).
5. Set the Keyframe Interval to 2 seconds (crucial for SRT stream stability).

Step 4: Start and Verify the Stream

1. Click Start Streaming in the main OBS window.
2. Monitor the status bar at the bottom right. A green square indicates a stable, secure connection.
3. Ensure that your receiving decoder (such as VLC, vMix, or a hardware decoder) is configured with the exact same passphrase and pbkeylen settings. If the encryption keys do not match, the receiver will not be able to decrypt and display the video feed.