Display Tile Caching for Reducing Bandwidth and Latency
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Solution Overview
Problem
Conventional methods for managing display data are inefficient, leading to high memory requirements, increased latency, and bandwidth usage due to the need to store and transfer redundant data across multiple frames, especially as display device resolution and connectivity increase.
Innovation Solution
A method that divides display data into tiles, uses caching to identify and reuse unchanged tiles, and transmits only changed tiles or their identifiers, reducing the need for redundant data transmission and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods store complete frame buffers in memory for display, then display data can be read and rastered directly onto the display device, but large areas of memory are dedicated to storage and memory requirements increase as display resolution and number of connected display devices increase
Solution Approach 1:
The frame buffer is divided into multiple tiles, where each tile represents a portion of the display data. This segmentation allows the system to process and transmit only specific tile data rather than entire frame buffers, reducing memory requirements and improving transmission efficiency.
Solution Approach 2:
The patent extracts only the changed tiles from the frame buffer for transmission, rather than transmitting complete frame buffers. This extraction process identifies which tiles have changed since the previous frame and transmits only those specific tiles, significantly reducing bandwidth usage and memory requirements.
2Speed
If complete frame buffers are prepared and transferred from external memory to local memory, then display data is available for rastering, but data transfers are slow and increase latency and bandwidth usage
Solution Approach 1:
The patent extracts only the changed tiles from external memory for transfer to local memory, rather than transferring complete frame buffers. This selective extraction reduces the volume of data transferred, thereby increasing transfer speed and reducing latency.
Solution Approach 2:
The system performs preliminary identification of changed tiles before the data transfer process begins. By pre-processing the frame buffer to identify which tiles have changed, the system prepares the minimal necessary data for transfer, reducing overall transfer time and latency.
3Productivity
If redundant data is transmitted across multiple frames, then display data can be continuously updated, but bandwidth usage increases and processing power is wasted on encoding and transmitting unchanged data
Solution Approach 1:
The patent extracts only the changed tiles from each frame for transmission, filtering out unchanged tiles. This extraction process eliminates redundant data transmission, reducing bandwidth usage and processing requirements while maintaining continuous display updates.
Solution Approach 2:
The system periodically identifies and transmits only the changed portions of the display data between frames. This periodic selective transmission, rather than continuous full-frame transmission, reduces bandwidth usage and processing energy while maintaining display refresh rates.
4Reliability
If multiple frame buffers are used with one being read and displayed while another is written to, then tearing is prevented, but memory requirements increase
Solution Approach 1:
The patent segments the frame buffer into tiles and applies caching mechanisms to store tile data. This segmentation allows the system to use fewer complete frame buffers while maintaining display stability, as changed tiles can be retrieved from cache rather than requiring full duplicate frame buffers.
Solution Approach 2:
The system changes the parameter of frame buffer management from storing complete frame buffers to storing individual tile data in cache. This parameter change reduces memory requirements while maintaining the ability to prevent tearing through dual-buffering techniques.
Data Source
AI summary
A method of managing display data involves maintaining caches (25, 29) of most recently used tiles of display data at a host (21) and at a display control device (22). The caches (25, 29) are synchronised so that they contain the same data in the same locations. When the host (21) generates a tile that needs encoding and transmitting, it checks to see if that tile is already stored in the host cache (25). If so, it sends a cache ID to the display control device (22); otherwise, it encodes and sends the tile. When the display control device (22) receives data, it identifies it either as a cache ID or as an encoded tile. If it is a cache ID, the data is retrieved from the display control device cache (29) and sent for display (23); otherwise, it decodes the tile and sends it for display (23). Both caches (25, 29) are updated so that the tile is indicated as the most recently accessed item in each cache (25, 29).