Networking audio

Introduction

This page deals with sending audio to distant clients through the network. The network in question is a LAN this does not cover contacting clients over the Internet. With proper NAT and firewall setup this could be possible but first you have to make sure it works on the LAN.

The preferred transport and protocol is RTP over UDP.

The audio preferences menu

Details of the settings are covered here: https://github.com/f4exb/sdrangel/blob/master/sdrgui/audio.md The concerned settings are 5 to 14. The settings to consider at client side are:

• Address (11): this is the "remote" address i.e. the address of the network interface on the client that will receive the stream
• Port (12): this is the port at which the client listens
• Stream parameters (5, 8, 9): these settings result in a format described in SDP form at (10)
• You will want to check the RTP flag (14) to transmit using RTP protocol

Receiving the stream in a client application

You may use VLC, cvlc or MX Player for example. MX player is recommended on Android clients. All these applications will read a .sdp file as input. This is a text file that describes the stream. For example:

c=IN IP4 192.168.1.3
m=audio 9998 RTP/AVP 96 
a=rtpmap:96 L16/48000/1

• 192.168.1.3 is the IPv4 address of the interface that receives the stream.
• 9998 is the port that receives the stream
• 96 is the RTP payload type