The digital radio DAB+ (Digital Audio Broadcast) must be assigned the capacity to broadcast with a high data rate, otherwise there is a risk for an inferior audio quality. This is one of the conclusions from research collaboration between Luleå University of Technology and Swedish Radio. The results are published in the latest issue of Journal of the Audio Engineering Society.
"We have indications showing that close to 300 kilobit per second would be needed to get what is referred to as a perceptually transparent system where no quality degradations can be noticed," says Jan Berg, associate professor at Luleå University of Technology, who has been responsible for the research project.
The digital solution DAB+, the forthcoming system for digital radio, is comparable to an ordinary FM-system down to 160 kilobit/second. Below that rate, the quality is significantly degraded. In the project that has been going on for two years, with 5 people involved, several tests have been made with experienced listeners as participants. These have assessed the audio quality according to international recommendations. The tests show that data rates close to what is maximally available in DAB+ should be used.
"If you aim to compete with a high-quality FM system, you should run DAB+ at its maximum of 192 kilobit/second in order to maintain the quality for sounds that are typical and frequently occurring in broadcasting," says Jan Berg.
The paper identifies two conflicting targets: the high data rate required to achieve good sounding digital radio, and the demand for capacity to make room for more radio channels, both within the same bandwidth.
"Therefore this study is important for those who will decide on the allocation of the data rate," says Lars Jonsson, technology strategist at Swedish Radio, one of the participants in the project.
In the published paper, it is also established that there are several services offering audio that is coded with higher data rates and that this puts pressure on the audio quality of the digital radio not to be inferior.
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