On Ultra Low-Delay Compression of Higher Order Ambisonics Signals

The challenge of coding delay is becoming increasingly recognized as a barrier to the broader implementation of Higher Order Ambisonics (HOA), which is a highly flexible format for spatial audio encoding and reproduction. A low latency is essential for various applications, such as virtual reality, interactive gaming, and live online music sessions. Unfortunately, significant strides in the development of spatial audio codecs often compromise on latency to enhance compression efficiency. This work presents a low-delay codec designed for the compression of HOA signals. The codec uses a combination of singular value decomposition, short-term linear prediction, cascaded long-term prediction, and sub-band coding, as well as entropy coding, in order to maximally compress HOA signals while maintaining a low delay. A variety of configurations allow for algorithmic delays between 54 samples to 206 samples, at the cost of bitrate given a fixed quality level. The proposed codec outperforms the low-delay implementation of a standard codec for HOA lossy compression, both in terms of delay and bitrate at medium and higher quality levels.