Compact NAL Unit Header Encoding for Video Decoding

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The current NAL unit header in HEVC and VVC requires two bytes, with the second byte often containing unnecessary zero bits, and many NAL unit type values are reserved or unused, leading to inefficient bit usage.

Innovation Solution

The proposed solution is to use a more compact representation of the NAL unit header by signaling the NAL unit type with one or two codewords in the first byte, and only using a NAL unit header extension for less frequently used NAL unit types, thereby reducing bit usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the NAL unit header uses two bytes for all NAL unit types, then all NAL unit types can be represented, but bit efficiency deteriorates because many NAL unit types are reserved or unused and the second byte contains unnecessary zero bits

Engineering Contradiction:

Improvebit usageVSAvoidNAL unit type representation

Core Design Contradiction:

Quantity of substanceVSAdaptability or versatility

Solution Approach 1:

The NAL unit header is segmented into a first part (always present) and a second part (extension, present only when needed). The first part contains the essential NAL unit type information that can be represented with one byte, while the second part extends the representation only for less frequently used NAL unit types, achieving both bit efficiency and complete type representation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The NAL unit header structure is made dynamic rather than fixed. The presence of the second part varies based on the specific NAL unit type being represented. Common NAL unit types use only the first part, while less frequent types trigger the second part, allowing the header size to adapt to the actual data requirements.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the NAL unit header extension is used for all NAL unit types, then complete NAL unit type representation is achieved, but bit efficiency deteriorates due to unnecessary extension bits for common types

Engineering Contradiction:

ImproveNAL unit type representationVSAvoidbit usage

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

Different parts of the NAL unit header have different qualities or properties. The first part provides basic representation for all types, while the second part provides enhanced representation only for specific subsets of types (less frequently used ones). This local differentiation optimizes bit usage by applying extension only where necessary.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The extension mechanism applies partial action by being selectively activated only for less frequently used NAL unit types rather than being universally applied to all types. This partial application avoids excessive bit usage for common types while still providing complete representation capability when needed.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS12267511B2Compact network abstraction layer (NAL) unit header

Publication Date: 2025.04.01 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

There are provided mechanisms performed by a video decoder. The method comprises obtaining a network abstraction layer (NAL) unit having a particular NAL unit type. The obtained NAL unit comprises a NAL unit header. The NAL unit header of the obtained NAL unit comprises at least a first part comprising N bits. The method comprises obtaining NAL unit header (NUH) extension information that indicates whether or not the NAL unit header further comprises a second part that comprises M bits. The method comprises determining, based on the NUH extension information, a NAL unit type value specifying the particular NAL unit type of the obtained NAL unit.