Perceptual Evaluation of Higher-Order Ambisonic Codecs on Both Synthetic Mixing and Native Recordings

Abstract: Spatial audio is spreading in applications such as virtual and augmented reality and immersive games. The higher-order ambisonic (HOA) format is particularly useful in this context. Transmitting spatial information requires multiple channels, e.g., 16 channels for 3rd-order ambisonics, resulting in increased memory requirements for storage and higher bitrates for communication. Therefore, efficient compression algorithms are necessary for those contents. The recently standardized IVAS codec allows the coding of HOA content for communication use-cases. Here, we propose to evaluate it in comparison with a basic multi-mono approach across a variety of contents and spatialization methods. Results show that IVAS outperforms the multi-mono approach at the same bitrate. In particular, this codec exploits inter-channel correlation to reduce the bitrate. We point out that it is therefore especially robust for signals with a high interchannel correlation, such as those composed of a limited number of plane waves. Conversely, the multi-mono approach is unable to exploit this correlation and performs poorly on this type of signal.