The Influence of the Bitrate Level on the Subjective Sound Quality Perception of the Concatenated Non-Entropic Audio Coding Algorithms in the Digital Broadcasting Chain

摘要

Digital Audio Broadcasting (DAB) and all similar systems for digital radio and television broadcasting are inevitably associated with lossy psychoacoustic audio compression. The coding algorithms are continuously being improved. To achieve high sound quality a lower bitrate, required by the broadcasters, is now sufficient. This paper compares the relevant digital audio codecs: MPEG 2 and AAC in three profiles (AAC LC, HE-AAC v1 and HE-AAC v2). The well-known MP3 format is also added for a better comparison. A brief description of the basic functional principles of the codecs is followed by a comparison of their efficiency keeping in mind the subjectively comparable sound quality. The main contribution of this paper is the verification of the relationship of the bitrate level and sound quality in broadcasting environment and the finding out the influence of other, often more significant factors, such as the primary quality of the input recordings and the concatenation of non-entropic coding, on the subjective perception in the digital broadcasting chain. These findings are supported by the results of a unique research analysis providing an insight into which specific audio encoding configurations are used for DAB+ radio broadcasting in practice, in Europe as a whole and in individual European countries.