NAL Header Layer ID Extension for Scalable Video Decoding
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Solution Overview
Problem
Existing video coding technologies, such as MPEG and ITU-T, do not provide a suitable mechanism for extending the number of layer ID values for the NAL units, leading to inefficiencies and inflexibility in handling a sufficient number of layer ID values.
Innovation Solution
Incorporating an optional extension value in the NAL header to generate layer ID values using multiple values derived from first syntax elements, such as V0+ (F−V0)*2N+S or V0+ ((F−V0)<<N+S, where F is the value of the one or more first syntax elements, V0 is the start value, N is the number of bits used for the second syntax elements, and S is the value of the second syntax elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing video coding technologies (MPEG, ITU-T HEVC) are used without extension mechanisms, then the NAL unit header structure remains simple and standardized, but the number of layer ID values is insufficient and inflexible for handling a sufficient number of layers
Solution Approach 1:
The layer ID value is segmented into two parts: a first part stored in the nuh_layer_id field and a second part stored in the nuh_layer_id_extension_value field. This segmentation allows the system to maintain a simple base structure while extending capacity through optional extension fields, resolving the contradiction between simplicity and adaptability.
Solution Approach 2:
The patent extends the layer ID capacity by adding a temporal dimension through the extension value field. Instead of increasing the bit width of the original field (which would increase complexity), it adds a new dimension (extension field) that only activates when needed, maintaining backward compatibility while providing extended functionality.
2Adaptability or versatility
If the nuh_layer_id field width is increased to accommodate more layer ID values, then the range of layer ID values increases, but the bitstream size and processing complexity increase
Solution Approach 1:
The patent implements partial action by only adding the extension value field when additional layer ID capacity is needed. The extension field is conditional and only present in the bitstream when necessary, avoiding unnecessary bits in standard cases while providing extended range when required.
Solution Approach 2:
The extension field mechanism serves multiple functions: it maintains backward compatibility with existing decoders, provides extended layer ID capacity when needed, and keeps the bitstream compact for standard cases. This multi-functionality resolves the contradiction between range and size.
3Productivity
If a fixed-width nuh_layer_id field is used, then the NAL unit header structure is simple and processing is efficient, but the system cannot handle a sufficient number of layer ID values
Solution Approach 1:
The patent makes the NAL unit header dynamic by introducing a conditional extension field. The header structure adapts based on whether extension is needed: simple for standard cases, extended when additional layer ID capacity is required. This dynamic structure maintains decoding efficiency for common cases while providing adaptability when needed.
Solution Approach 2:
The patent changes the parameter structure by introducing an optional extension field that modifies the effective bit width of the layer ID representation. Instead of fixing the parameter width, it allows the parameter to effectively change size based on requirements, resolving the contradiction between efficiency and adaptability.
Data Source
AI summary
A method of decoding an encoded image includes obtaining a layer identification, Layer ID, indicator from a first field of a header for a network abstraction layer, NAL, unit of the encoded image, determining whether the Layer ID indicator is less than a start value, in response to determining that the Layer ID indicator is not less than the start value, determining the Layer ID value based on the Layer ID indicator and based on an extension value provided in a second field of the header, and decoding the NAL unit based on the Layer ID value. Related decoders, encoding methods, encoders and computer program products are disclosed.