An essential architectural characteristic of XR clients is the reliance on a functional split between a set of composite pre-renderers that are implemented as parts of a presentation engine and a set of post-rendering operations implemented on an End Device prior to final output. Split rendering may be a necessity if the End Device is power constrained or limited in computational power. However, split rendering is not precluded from other End Devices that do not have such constraints. Nonetheless, throughout this this TR, when referring to the End Device in split rendering context, it may also be called lightweight End Device or lightweight UE. The functional split assumed in split renderer architectures is a result of stringent implementation and operational requirements applicable for rendering of XR media on XR devices. For head-tracked immersive audio, the need to rely on a split renderer architecture, may depend on various factors among which the round-trip latency on the interface between the renderer in the presentation engine and the lightweight End Device is a decisive parameter. There are scenarios where this latency may be substantial which may make preferable a split rendering approach with pose correction in the End Device for binaural audio in a similar way as for video unless decoding and head-tracked binaural audio rendering on the lightweight End Device does not exceed its strict complexity constraints. In other scenarios, that latency may be sufficiently low, in which case the head-tracked binaural rendering can exclusively be done in the presentation engine. It is notable that the transmission over the interface may generally be bit rate constrained and dependent on the specific physical interface properties. Technical solutions for the provision of immersive audio in split rendering scenarios are largely dependent on the associated properties and imposed requirements, which are identified by the present TR.

The present document identifies relevant guidelines and IVAS [2] related requirements associated with split rendering scenarios for immersive audio. It covers:

• Design guidelines/constraints related to complexity and memory as well as constraints related to relevant interfaces between presentation engine and End Device such as bit rate, latency, down- and upstream traffic characteristics.
• Design guidelines/constraints related to functional capability requirements such as rendering of non-diegetic sounds, 3DoF rendering of diegetic immersive sounds.
• Performance guidelines/requirements.

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