Scalable Video Encoding via Residual Downsampling
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Solution Overview
Problem
Existing video coding technologies face challenges in providing scalable complexity while maintaining high coding efficiency, particularly for diverse user devices with varying resolution requirements, leading to increased bitrate and complexity in encoders and decoders.
Innovation Solution
The method involves forming a motion-compensated full-resolution prediction, downsampling the prediction residual, and coding the low-resolution downsampled residual, allowing for scalable video encoding that supports diverse user devices with reduced complexity and bitrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If simulcast encoding is used to support diverse user devices with different resolution requirements, then device compatibility is improved, but total bitrate increases
Solution Approach 1:
The video bitstream is segmented into multiple scalability layers (base layer and enhancement layers) with different resolution and quality characteristics. The base layer provides low-resolution video suitable for mobile devices, while enhancement layers add additional resolution and quality for devices capable of processing them. This segmentation allows a single broadcast to serve multiple device types without requiring separate simulcast streams.
Solution Approach 2:
The scalability layers are nested within each other in a hierarchical structure where the base layer is contained within the enhancement layer. The enhancement layer includes all the information from the base layer plus additional data for higher resolution and quality. This nested structure enables progressive decoding where devices can process only the base layer or combine base layer with enhancement layers based on their capabilities, eliminating the need for separate simulcast broadcasts.
2Adaptability or versatility
If spatial scalability encoding is used to provide multiple resolution versions, then device compatibility is improved, but encoder and decoder complexity increases
Solution Approach 1:
The encoder and decoder are designed with dynamic adaptability to handle different scalability layers without requiring completely separate processing paths. The decoder can dynamically switch between processing only the base layer or combining base layer with enhancement layers based on device capabilities. This dynamic approach reduces complexity compared to implementing fully separate encoders and decoders for each resolution level while maintaining support for multiple device types.
3Adaptability or versatility
If traditional scalable coding methods are used, then resolution scalability is improved, but coding efficiency decreases
Solution Approach 1:
The enhancement layer applies local quality enhancement by selectively processing only the residual information and motion compensation data that adds value to the base layer. Rather than re-encoding the entire video at high resolution, the system enhances only the differences between resolution levels, improving coding efficiency while maintaining resolution scalability.
Solution Approach 2:
The system changes encoding parameters adaptively across different scalability layers. The base layer uses parameters optimized for low-resolution playback on mobile devices, while enhancement layers use parameters optimized for high-resolution display. This parameter adaptation allows each layer to be encoded efficiently for its target application, improving overall coding efficiency compared to using a single set of parameters for all resolutions.
Data Source
AI summary
A video decoder, a video decoding method, a video encoder and a video encoding method are disclosed. A video decoder for decoding a video bitstream for an image block includes a motion vector resolution reducer and a motion compensator. The motion vector resolution reducer is for receiving decoded high resolution motion vectors included in the video bitstream and for reducing an accuracy of the high resolution motion vectors to correspond to a low resolution. The motion compensator, in signal communication with the motion vector resolution reducer, is for forming a motion compensated high resolution prediction using the reduced accuracy motion vectors. The video encoder for encoding scalable video comprises a motion compensator for forming a motion compensated full resolution prediction and combining the motion compensated full resolution prediction from an image block to form a prediction residual. The prediction residual is downsampled to form a low resolution downsampled prediction residual and then coded.