Summary of S4-260109: Reproduction of Immersive Scenes for Testing

Introduction and Background

This discussion paper from HEAD acoustics addresses challenges in testing immersive capture performance of UEs under the ATIAS_Ph3-MED work item. While ATIAS_Ph2 introduced acoustic tests for transparent UE capture using ETSI TS 103 224's 8.0/8.1-channel loudspeaker arrays, these systems lack sufficient spatial accuracy for immersive capture testing.

3GPP SA4 has liaised with ETSI TC STQ to extend ETSI TS 103 224 for immersive scene reproduction using higher-dimensional microphone and loudspeaker arrays. However, several open questions remain regarding implementation.

Use Cases and Test Setups

The paper identifies three physical/acoustical test setups currently defined in TS 26.260:

• Headset UE
• Handheld hands-free UE
• Table-mounted hands-free UE

Each setup covers both user capture and spatial capture scenarios (conversational vs. non-conversational services).

Open Questions Raised:

• Are any test setups/use cases missing?
• What is the priority ranking of use cases (most/least important)?
• Which scene types are appropriate for each use case (e.g., "rock concert" or "nature" may not suit table-mounted scenarios)?
• Are different immersive audio formats (type/complexity) required per use case?

Test Complexity Considerations

The document acknowledges that accurate immersive scene reproduction requires higher complexity than mono telephony UE testing. The IVAS codec supports formats like HOA3, establishing minimum reproduction system requirements. The general principle proposed is that "immersive playback capabilities" should preferably exceed the "immersive capture capabilities" of the UE under test.

Complexity Adaptation Examples:

Table-mounted UE with HOA3 capture: - Since a test table is part of the setup, a loudspeaker array covering only a half-sphere might be sufficient

Handheld hands-free UE: - State-of-the-art mobile phones in coming years will likely have only ~5-6 microphones - May not support capture/render/transmission of real HOA3 - Question raised whether sound field simulation systems must reproduce HOA4 accurately for such devices

Audio Material for Testing

Similar to recent transparent capture testing extensions in TS 26.260, a range of immersive scenes should be tested. ETSI TS 103 224 provides an audio material database for this purpose.

Identified Challenges:

• During transparency test drafting, certain desired scenes/noise types (covering specific level ranges, dynamics, immersive cues) could not be identified in existing databases
• The same issue may arise for immersive audio format test methods
• While collecting suitable audio material is within ETSI STQ's scope for extending ETSI TS 103 224, availability by end of Release-20 (conclusion of ATIAS_Ph3-MED) depends on user contributions
• Several publicly available databases exist, but license terms often prohibit commercial usage

Conclusion

The paper highlights challenges in introducing immersive sound field reproduction for testing UE capture performance—a major goal of ATIAS_Ph3-MED. Some open questions may be resolved quickly through discussion, while others require further investigation. The source specifically invites delegates to contribute audio material for testing (with license terms/conditions to be confirmed).