Palette Coding Quantization for Screen Content Compression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional video coding techniques are inefficient for compressing screen content with discrete-tone characteristics, such as text or computer graphics, as they assume continuous-tone and spatial smoothness, which is not applicable to screen-generated content.
Innovation Solution
Palette-based coding techniques are used, where a palette of dominant colors is created to represent video data, and index values are encoded instead of actual pixel values, with specific methods for deblocking filtering and quantization parameter determination at video encoders and decoders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional video coding techniques are used for screen content, then the coding process is simple, but compression efficiency is poor because the techniques assume continuous-tone and spatial smoothness which does not apply to discrete-tone screen content
Solution Approach 1:
The patent segments the video content identification process by using a content identifier to distinguish between natural video content and screen content. This segmentation allows different coding techniques to be applied to different content types, improving compression efficiency for screen content while maintaining simplicity for natural content.
Solution Approach 2:
The patent changes coding parameters based on content type identification. When screen content is detected, specific coding parameters are adjusted to suit discrete-tone characteristics, thereby improving compression efficiency without unnecessarily complicating the coding of natural content.
2Object-affected harmful factors
If deblocking filtering is applied to palette-coded blocks, then block artifacts may be reduced, but distortion is introduced to the discrete-tone content which degrades quality
Solution Approach 1:
The patent applies preliminary anti-action by identifying palette-coded blocks before filtering and preventing deblocking filtering from being applied to them. This preemptive measure avoids the introduction of distortion to discrete-tone content while still allowing filtering to be applied to other block types where it is beneficial.
Solution Approach 2:
The patent applies different filtering treatments to different block types based on their characteristics. Palette-coded blocks are excluded from deblocking filtering to preserve their discrete-tone quality, while other blocks may receive filtering to reduce artifacts,从而实现局部优化的质量控制。
3Productivity
If quantization is applied to escape pixel values in palette-coded blocks, then compression is improved, but quantization noise is introduced which reduces image quality
Solution Approach 1:
The patent applies partial quantization by distinguishing between palette indices and escape pixel values. Palette indices are protected from quantization to maintain exact color representation, while escape pixel values undergo quantization to achieve compression. This selective approach balances compression needs with quality preservation.
4Productivity
If palette-based coding is used for screen content, then compression efficiency is improved, but the coding and decoding process becomes more complex
Solution Approach 1:
The patent performs preliminary action by pre-identifying screen content regions and determining their suitability for palette-based coding before the actual coding process. This advance preparation allows the system to efficiently apply palette coding only where beneficial, reducing overall complexity while maintaining compression efficiency gains.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Techniques are described for palette-based video coding. In palette-based coding, a video coder may form a so-called "palette" as a table of colors for representing video data of a given block of video data. Rather than coding actual pixel values or their residuals for the given block, the video coder may code index values for one or more of the pixels. The index values map the pixels to entries in the palette representing the colors of the pixels. Techniques are described for determining the application of deblocking filtering for pixels of palette coded blocks at a video encoder or a video decoder. In addition, techniques are described for determining quantization parameter (QP) values and delta QP values used to quantize escape pixel values of palette coded blocks at the video encoder or the video decoder.