Set RIST Buffer and Encryption in FFmpeg

This guide explains how to configure the packet recovery buffer size and encryption key for the Reliable Internet Stream Transport (RIST) protocol using FFmpeg. You will learn the specific URL parameters required to secure your stream with AES encryption and set up an optimal retransmission buffer to prevent packet loss over unstable networks.

RIST Configuration Parameters

FFmpeg configures RIST options directly within the output or input URL query string. To configure the packet recovery buffer and encryption, you will use three primary parameters:

• buffer: Sets the packet recovery buffer size (retransmission queue) in milliseconds. This determines how long the stream can tolerate network drops.
• secret: Defines the pre-shared passphrase used for stream encryption.
• aes_type: Specifies the AES encryption strength. Supported values are 128 or 256 (representing AES-128 and AES-256).

FFmpeg Command Syntax

The parameters are appended to the RIST URL using the standard query string format (?param1=value1&param2=value2).

1. Streaming Out (Sender)

To stream a file to a remote RIST receiver with a 1000ms (1 second) packet recovery buffer and 256-bit AES encryption, use the following command:

ffmpeg -re -i input.mp4 -f mpegts "rist://192.168.1.50:5000?buffer=1000&secret=MySecurePassword123&aes_type=256"

2. Receiving the Stream (Receiver)

To receive the encrypted stream, the receiver must use matching buffer and encryption settings. If the receiver is listening for incoming connections, add the listen=1 parameter:

ffmpeg -i "rist://0.0.0.0:5000?buffer=1000&secret=MySecurePassword123&aes_type=256&listen=1" -c copy output.mp4

Important Considerations

• Buffer Size: The buffer value should be set to at least 2.5 times the round-trip time (RTT) of your network path for effective Automatic Repeat reQuest (ARQ) packet recovery.
• Secret Key Length: The secret password must be between 8 and 128 characters long.
• Protocol Support: Ensure your FFmpeg build is compiled with RIST support (compiled with --enable-librist). You can verify this by running ffmpeg -protocols and checking if rist is listed.