Host Content Adaptive Backlight Control for HMDs
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Solution Overview
Problem
Conventional content adaptive backlight control (CABC) techniques in head-mounted display (HMD) devices suffer from lag, resulting in noticeable artifacts due to the delayed calculation of backlight dimming based on previous frame image data, which affects image quality and user experience.
Innovation Solution
Implementing a system where the host device generates and transmits concurrent backlight configuration data with pixel data, allowing the display device to update both the pixel elements and backlight intensity simultaneously for each frame, using techniques like 2-bits per pixel sparse encoding and compression to ensure synchronized processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CABC techniques are implemented by the display driver calculating backlight intensity based on previous frame image data, then power consumption is reduced and image quality is enhanced, but a lag occurs resulting in noticeable artifacts
Solution Approach 1:
The host device calculates the backlight configuration data in advance based on the current frame image data before transmitting it to the display device. This preliminary calculation allows the backlight intensity to be adjusted concurrently with the pixel updates, eliminating the one-frame lag inherent in conventional display driver-based CABC implementations.
2Reliability
If the host device generates and transmits concurrent backlight configuration data with pixel data, then the backlight intensity is adjusted in real-time improving image quality, but the device complexity and data transmission requirements increase
Solution Approach 1:
The backlight configuration data is merged with the pixel data into a single frame buffer image that is transmitted from the host device to the display device. This combining approach allows concurrent backlight control information to be sent along with the display data without requiring separate communication channels or increasing overall system complexity.
Solution Approach 2:
The frame buffer image serves multiple functions: it contains both the pixel data for display and the embedded backlight configuration data for backlight control. This multi-functionality allows a single data structure to accomplish both display rendering and backlight synchronization tasks.
3Reliability
If backlight configuration data is embedded in the frame buffer image, then concurrent updates are achieved, but the data processing and encoding complexity increases
Solution Approach 1:
The frame buffer image is segmented into different regions: a first region containing pixel data and a second region containing backlight configuration data. This segmentation allows the display device to efficiently extract and process the relevant data portions without dealing with the entire frame buffer, reducing processing complexity while maintaining synchronization.
Data Source
AI summary
A method and apparatus for content adaptive backlight control (CABC) is disclosed. A display device comprises a display surface including a plurality of pixel elements and a backlight configured to illuminate the display surface. A display driver of the display device is configured to receive a frame of display data, including pixel data for displaying an image on the display surface and backlight configuration data for adjusting the backlight when displaying the image. The display driver is further configured to update the plurality of pixel elements using the pixel data, and update an intensity of the backlight using the backlight configuration data. More specifically, the updates to the backlight and the display surface are performed concurrently for the received frame of display data.