engleski

SOURCE AUDIO CODING IN DIGITAL RADIO MONDIALE

Digital Radio Mondiale (DRM) is a new digital radio broadcasting system originally intended for use at frequencies below 30 MHz, while efforts are made to extend the use of the system to the frequency range up to 120 MHz. The purpose of developing and introducing this system is to replace all existing analog radio broadcasting systems operating in the fore mentioned frequency range. Furthermore, the system is fully incorporated in the existing frequency plan for easier implementation, thereby using standard AM channels of 9 (10) kHz bandwidth or half-channels of 4.5 (5) kHz width. In some cases, when allowed by the frequency plan, double channels of 18 (20) kHz width can be used. In any case, the usable bandwidth is rather narrow, which represented a big obstacle for realization of DRM for a long time. This was due to the lack of audio coding methods efficient enough to compress the source audio signal to a size acceptable for transmission in the mentioned bandwidth, while maintaining a reasonable sound quality. Finally, the development of MPEG-4 Audio standard opened up the possibility to overcome this problem and offer interference-free listening at near-FM quality, covering great distances with a single transmitter. The methods of source coding for audio signals defined in the MPEG-4 standard and modified for specific use in DRM system will be presented in this paper.

DRM; source coding; audio signal

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