Required bit rate of MPEG-4 AAC for 22.2 multichannel sound contribution and distribution

摘要

22.2 multichannel sound (22.2 ch sound) is currently broadcast using MPEG-4 Advanced Audio Coding (AAC) in 8K Super Hi-Vision broadcasting in Japan. The use of MPEG-4 AAC for contribution and distribution transmissions is also planned. Contribution and distribution transmissions require sufficient audio quality to withstand repeated coding and decoding processes. In this study, the bit rate of MPEG-4 AAC for a 22.2 ch sound signal satisfying tandem transmission quality was investigated by the subjective evaluation specified in Recommendation ITU-R BS.l 116-3. The basic audio quality of 72 stimuli made from a combination of six bit rates, three different numbers of tandems, and four contents were evaluated by 28 listeners. The required bit rates of 22.2 sound material transmission for three, five and seven tandems were concluded to be 96, 144, and 160 kbit/s per channel, respectively.