Multi-channel Production For Radio

File Formats

Multi-channel audio is stored in WAV files on hard disks. Existing computer and IP based production infrastructures can be used and 5.1 files can be transmitted and retrieved like normal audio material. If the system is properly designed, the mixing software, which is part of most digital audio production systems, can be used. If not, any audio treatment must be carried out in an external mixing console.

It would be highly desirable to develop a BWF format for multi-channel audio. It should be designed to carry multi-channel and stereo mixes in the same file. Swedish Radio would prefer using DTS for 5.1 or 6.1 mixes at about 1.5 Mbit/s. Layer 2 coding at minimum 384 kbit/s could be used for the stereo mix.

Coding Aspects

It is virtually impossible to avoid cascading in radio broadcasting, especially in live transmissions. 5.1 channel DTS 96/24 at 1.5 Mbit/s offers excellent audio quality and cascadeability.

Transmission

SR operates an extensive real-time contribution network based on ITU-R J.57 codecs, which are transparent to 1.5 Mbit/s DTS signals. Coders and decoders connect directly to the J.57 devices. No other equipment is needed to convert the dual-channel network to a high-quality 5.1 or 6.1- channel network.

DTS provides an all-digital chain for transparent transmission and broadcasting of 96/24 signals from the studio to the home. Due to instrumental reasons, decoding of DTS signals is needed in order to handle them in SR's continuity control. Any non-DTS signals en route would probably introduce serious drawbacks in terms of reduced quality and indeed higher costs.