Loudness-Level-Chasing Algorithm for Multiformat Live Audio Production

This paper proposes a loudness-level-chasing algorithm for live audio production to manage an integrated loudness level of a downmixed (DMX) signal produced from an immersive audio (IA) signal. The purpose of this study is to establish a method to simulcast the IA and DMX signals at the same integrated loudness level without manual operation. The proposed algorithm derives an adjustment coefficient applied to the amplitude of the DMX signal, taking the difference of the temporary integrated loudness levels of the IA and DMX signals and the remaining time of the program into consideration. The adjustment coefficient is iteratively updated throughout the program and is sequentially applied to the incoming DMX signal. The effectiveness of the adjustment in accordance with the proposed algorithm is verified using four 22.2 multichannel (22.2 ch) sound programs as the IA signals. The DMX signals are produced in the stereo format from the 22.2 ch sound signals using a downmixing method. Simulation experiments confirm that the proposed algorithm adjusts the integrated loudness level of the DMX signal within a deviation of $\pm$0.1 dB from that of the 22.2 ch sound signal. In addition, the results of subjective evaluation carried out by professional sound engineers proves that the adjustment in accordance with the proposed algorithm is non-annoying for listeners if a transition rate of the adjustment coefficient is in the range of 0.1 to 3 dB/s. In summary, the proposed algorithm can effectively manage the integrated loudness level of multiformat audio in live productions.