Mixed NAL Unit Video Coding for Efficient Subpicture Transmission
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Solution Overview
Problem
The increasing demand for high-resolution and high-quality images leads to a significant increase in transmission and storage costs due to the rise in the amount of transmitted information, necessitating high-efficient image compression technologies.
Innovation Solution
An image encoding and decoding method and apparatus based on mixed NAL unit types, allowing for the partitioning of a current picture into subpictures with different NAL unit types, and determining the NAL unit type of each slice based on the VCL NAL unit type information to enhance encoding and decoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-resolution and high-quality images are transmitted, then image quality is improved, but transmission cost and storage cost increase
Solution Approach 1:
The current picture is divided into multiple subpictures, each with different NAL unit types (e.g., RASL, RADL, TRAIL). This segmentation allows different regions of the image to be encoded with different compression levels and accessibilities, enabling selective transmission of critical regions while compressing less important areas, thus reducing overall transmission data while maintaining perceived image quality.
Solution Approach 2:
Different subpictures within the same picture are assigned different NAL unit types with different quality characteristics. For example, RASL subpictures provide random access with lower quality, while RADL subpictures provide decoded leading quality. This local quality differentiation allows the system to optimize transmission by sending high-quality data only where necessary and lower-quality data elsewhere, reducing total transmission volume while maintaining acceptable overall image quality.
2Productivity
If multiple subpictures with different NAL unit types are used, then encoding efficiency is improved, but device complexity increases
Solution Approach 1:
The NAL unit type for each subpicture is determined in advance during the encoding phase based on predefined criteria and picture characteristics. This preliminary determination allows the encoder to optimize the bitstream structure before transmission, improving encoding efficiency by selecting appropriate compression parameters for each subpicture region without requiring complex real-time decisions during decoding.
Solution Approach 2:
The decoding apparatus determines the NAL unit type of the current picture by analyzing the bitstream structure and VCL NAL unit type information already present in the transmitted data. This self-service approach allows the decoder to automatically adapt to different subpicture types without requiring additional complex control signals or external information, thereby improving encoding efficiency while limiting the increase in device complexity.
Data Source
AI summary
Disclosed herein are an image encoding and decoding method and apparatus. The image decoding method may include obtaining video coding layer (VCL) network abstraction layer (NAL) unit type information of a current picture from a bitstream, determining a NAL unit type of each of a plurality of slices included in the current picture, based on the obtained VCL NAL unit type information, and decoding the plurality of slices based on the determined NAL unit type. The current picture may include a first subpicture and a second subpicture having different NAL unit types based on that at least some of the plurality of slices have different NAL unit types, and a NAL unit type of the second subpicture may be determined based on a NAL unit type of the first subpicture.