IVAS Bitstream Structure for Immersive Audio Mode Flexibility
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Solution Overview
Problem
Existing voice and video encoder/decoder (codec) standards lack efficient and robust bitstream formats for immersive voice and audio services (IVAS) that support a range of audio service capabilities, including mono to stereo upmixing and fully immersive audio encoding, decoding, and rendering across various devices and network nodes.
Innovation Solution
The implementation of an IVAS bitstream format that includes a common header (CH), tool header (TH), metadata payload (MDP), and EVS payload (EP) sections, enabling efficient encoding and decoding of spatial metadata and EVS coded bits for immersive audio signals, with bitrate distribution control and quantization strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a unified codec standard is used for traditional audio services, then device compatibility is maintained, but it cannot efficiently support immersive audio services with spatial metadata and multiple coding modes
Solution Approach 1:
The bitstream is divided into distinct sections including Common Header (CH), Tool Header (TH), Metadata Payload (MDP), and Enhanced Voice Services Payload (EP). Each section serves a specific function: CH contains global parameters, TH contains tool-specific parameters, MDP contains spatial metadata, and EP contains coded audio bits. This segmentation allows the system to support immersive audio services while maintaining clear structure and device compatibility.
Solution Approach 2:
The IVAS bitstream format is designed to be universal, supporting multiple coding modes (mono, stereo, immersive audio) and various device types within a single standardized format. The flexible structure with optional sections and parameter indicators enables the same bitstream format to serve both traditional audio services and advanced immersive audio services across diverse devices including mobile phones, tablets, computers, and VR/AR devices.
2Adaptability or versatility
If spatial metadata and multiple coding modes are supported, then immersive audio capability is enhanced, but bitstream processing complexity increases
Solution Approach 1:
The bitstream format incorporates dynamic elements including mode indicators that specify the current coding mode (mono, stereo, or immersive), quantization strategy indicators that adapt to different bitrate requirements, and tool header sections that are conditionally present based on the selected coding mode. This dynamic structure allows the encoder and decoder to efficiently process only the relevant parameters for the active coding mode, reducing processing complexity while maintaining support for multiple modes.
3Manufacturing precision
If bitrate distribution control and quantization strategies are implemented, then audio quality is improved, but processing overhead increases
Solution Approach 1:
The Common Header section contains pre-calculated parameters including bitrate distribution control information and quantization strategy indicators that are determined before the actual audio coding process. These preliminary parameters guide the subsequent encoding and decoding operations, allowing the system to achieve high audio quality through controlled bitrate allocation and appropriate quantization without requiring complex real-time processing decisions during the main coding loop.
Data Source
AI summary
Encoding/decoding an immersive voice and audio services (IVAS) bitstream comprises: encoding/decoding a coding mode indicator in a common header (CH) section of an IVAS bitstream, encoding/decoding a mode header or tool header in the tool header (TH) section of the bitstream, the TH section following the CH section, encoding/decoding a metadata payload in a metadata payload (MDP) section of the bitstream, the MDP section following the CH section, encoding/decoding an enhanced voice services (EVS) payload in an EVS payload (EP) section of the bitstream, the EP section following the CH section, and on the encoder side, storing or streaming the encoded bitstream, and on the decoder side, controlling an audio decoder based on the coding mode, the tool header, the EVS payload, and the metadata payload or storing a representation of same.