C1 Studios

C1 Espresso is a cafe on High Street, near the Christchurch Polytech. Early in 2003 the owners, Sam and Fleur, undertook a project to set up a radio studio in the café. The studio is capable of streaming high-quality digital stereo audio as a remote studio for a radio station, and as an Internet radio station.

The studio was launched on 1 May 2003, in association with the local university's radio station RDU, by broadcasting pre-recorded music as well as live performances from the launch party in the evening.

The audio codecs and virtual private network system were all designed, built, installed and commissioned by Crystal Rock.

Physical Network

The communications system between C1 and the radio station is a Virtual Private Network (VPN) over the Internet (Figure 1).

Figure 1 - Physical Network

The Internet connection at C1 is a wireless link across High St to the Matrx office. This wireless link is provided by a Wifi router at Matrx and an 802.11b radio in the VPN server at C1.

Virtual Private Network

The VPN servers are Linux-based platforms with a secure encrypted tunnel over the Internet. All of the services required between the two sites are carried over this VPN, including:

• high-quality stereo audio
• IP telephony
• remote control

Audio Codecs

The audio codecs are Linux-based platforms with ogg vorbis encoding and decoding capabilities. These codecs are capable of serving an Internet radio stream with either ogg vorbis or MPEG layer 3.

IP Telephony

There is an IP telephone circuit at C1 Studios that is a virtual extension to the telephone exchange at the radio station. This telephone circuit is capable of forwarding up to four extensions.

The Voice-Over IP (VOIP) protocols are all handled by the VPN servers so that simple analogue connections can be used at each site. This means that any regular telephone can be used in the studio.