Summary of S4-260141: Target Platforms for ULBC

1. Introduction and Motivation

This contribution addresses a gap in TR 26.940 regarding target platforms for Ultra Low Bit rate Codec (ULBC) deployment. While the TR currently discusses NPU as a possible platform in clause 6.2.1.5.1, it lacks coverage of other non-NPU platforms. The document aims to complete this missing information, particularly focusing on DSP-enabled devices.

2. Technical Problem Statement

The contribution identifies an inconsistency in TR 26.940:

• Clause 6.2.1.1 states that the codec must support real-time processing alongside other audio processing units and should fit real-time resource constraints of CPUs, potential accelerators, and DSPs across a range of devices
• Clause 6.2.1.5.1 currently only describes NPU as a target platform, omitting DSP and other non-NPU platforms

The source references previous contributions (S4aA250267 and S4-251747) that discussed the need for DSP deployment and provided clarification on DSP-enabled UE devices.

3. DSP-Enabled Device Definition

The contribution adopts the definition from S4-251747 for DSP-enabled UE devices:

• Devices with DSP only or devices with multiple computing units including DSP
• For multi-unit devices (with CPU/NPU/DSP), there remains a preference for DSP deployment due to:
• Lower power consumption
• Reduced heat generation
• Better battery life
• Target devices include vehicle-mounted devices, glasses, and mobile phones with low computational capability
• DSP refers to audio processing DSPs available in mobile phones or other devices for voice communication

4. Proposed Text Changes

Main Technical Contribution

The proposal adds a new paragraph to clause 6.2.1.5.1 that:

1. Acknowledges vendor flexibility: Vendors may choose any computing unit to implement ULBC based on business needs or product constraints

2. Highlights DSP advantages:

3. Cheaper in terms of silicon real estate
4. Less power hungry
5. Less heat generation
6. Typically single-threaded for synchronized real-time execution with low overhead

7. Potentially wider range of product support

8. Establishes DSP deployment requirement: ULBC should be deployable on DSP-enabled UE devices, including:

9. Devices with DSP only

10. Devices with multiple computing units including DSP

11. Provides deployment rationale: Even when CPU or NPU are available, DSP may be preferred for power-sensitive applications (wearables, mobile phones)

12. Defines DSP computational power: Audio processing DSPs typically range from several hundred to over a thousand MIPS

Context Preservation

The proposal maintains the existing text about:
- NPU prevalence in modern smartphones
- NPU being 5-20x more power efficient than CPUs for AI tasks
- The note that ULBC may need to run on non-NPU platforms in certain configurations

5. Technical Impact

This contribution ensures that TR 26.940 provides comprehensive guidance on target platforms for ULBC deployment, balancing the AI-optimized NPU approach with the power-efficient DSP approach, thereby supporting a wider range of device implementations and use cases.