From Communications Components Magazine’s (Taiwan) special June issue on mobile phone components, I bring you “QuickLogic’s Visual Enhancement and Display Power Savings CSSP Chips Integrated into a Mobile Device”. A link to the original simplified-Chinese text is up at http://shop.quicklogic.com/in-the-news/, or you can access the file directly at http://shop.quicklogic.com/assets/press/CCM-Article.pdf
While this article is perhaps more review than anything else to avid readers of QuickLogic.com and blog.QuickLogic.com, there is a bit more detail on the software and drivers used in a CSSP implementation of VEE and DPO that we’ve shared in the past that you may find of interest. For those whose Chinese is, well, as good as mine (which is limited to ordering beer and saying thank you), the original English text is as follows:
Introduction
It is well recognized that a display will look its best when viewed in a dark room with the brightness set to maximum. However, maximum brightness translates into shorter system batter life, with the additional detraction of a lower display lifetime for OLED displays.
Typically, system designers will reduce brightness in order to lengthen battery life. However, reduction in display brightness leads to a degradation of image quality, particularly when ambient light ‘washes out’ the display content with reflected light. This effect is particularly pronounced with some newer OLED touchscreen displays, but is present on all commonly-used displays in mobile handsets, smartphones, tablets, and other handheld consumer devices?
So which path should a developer follow–allow the display to operate at increased brightness levels to increase viewability but sacrifice battery life; or conserve battery life but negatively affect the user experience in display viewability?
QuickLogic’s VEE (Visual Enhancement Engine) and DPO (Display Power Optimizer) proven system blocks (PSBs) can both increase display viewability in all lighting conditions while extending battery life. QuickLogic’s Visual Enhancement Engine technology greatly enhances the viewability of mobile device displays under challenging viewing conditions such as bright ambient light by dynamically optimizing video characteristics to provide a natural viewing experience, while DPO works in concert to reduce display backlight or power levels, extending system battery life as much as 41%.
QuickLogic CSSP Semiconductor Devices
QuickLogic introduced the CSSP (Customer Specific Standard Product) concept to the market back in 2007. A CSSP is a semiconductor device that can have a certain amount of dedicated functions contained (which is refer to this as hard logic), as well as a certain amount of area dedicated to customer-specific programming (referred to as programmable fabric). In QuickLogic’s ArcticLink II VX2, the hard logic contains the VEE and DPO technologies, as well as a PWM function. The remaining portion of the chip (fabric) is used to populate QuickLogic’s other technologies, or in some cases a customer’s technology.
A CSSP is not a pure ASIC (Application-Specific Integrated Circuit) or FGPA (Field Programmable Gate Array).
A CSSP differs from ASIC’s in the following ways:
A CSSP differs from an FPGA in the following ways:
VEE and DPO Functionality
QuickLogic’s Visual Enhancement Engine (VEE) technology enables a television-quality visual experience on portable devices. This technology delivers the next generation of mobile entertainment experience by adapting display data, in real-time, to improve the users viewing experience under difficult conditions like low backlight or in bright ambient light. QuickLogic’s proven VEE solution greatly enhances image and video quality for handset users by compressing the dynamic range to match the characteristics of the display, resulting in a substantially better viewing experience
QuickLogic VEE technology is based on the iridix® algorithm from Apical Limited. iridix is an implementation of a set of algorithms based on the Orthogonal Retina-Morphic Image Transform (ORMIT), developed by Apical and protected by multiple patents. It is a sophisticated method of dynamic range compression (DRC), which differs from conventional methods such as gamma correction in that it applies different tonal and color transformations to every pixel in an displayed image, video, or mixed content. These algorithms implement a model of human perception, which results in a displayed image that retains detail, color and vitality even under difficult viewing conditions. VEE technology specifically addresses the problem of the low contrast ratio of mobile displays to bring a more television-like viewing experience to mobile devices.
While the VEE uses statistical information gathered pixel-by-pixel, frame-by-frame to adjust the value of individual pixels, QuickLogic’s Display Power Optimizer (DPO) uses that same information to adjust the backlight. The ability to provide a unique tone curve for each pixel, as well as have tight control over the display backlight, gives greater flexibility than the global adjustments of alternative implementations. The QuickLogic approach results in greater power savings and the entirely new capability of adapting to a bright environment. DPO seamlessly integrates with the QuickLogic VEE, ensuring longer battery life and an excellent visual experience by coupling the PWM driving the display backlight with the display content processing parameters of the VEE technology.
CSSP Integration into a Smartphone or Tablet Device
Hardware
VEE and DPO are hardware based technologies, integrated into consumer devices via a CSSP (Customer Specific Standard Product) chip from QuickLogic. The CSSP is placed in the display path, between the CPU/Applications Processor and the display, as shown in Figure 2.
As shown in Figure 2, the CSSP chip receives the display data directly from the applications processor. Ambient light information is gathered either through direct i2c communication with the ambient light sensor (ALS), or through the applications processor over i2c.
QuickLogic’s CSSP chips are designed to be CPU-independent, requiring allocation of no processing resources from the host system. Additionally, they require no special peripheral circuitry to operate, making integration into a smartphone or tablet design a very quick and easy task.
Finally, as VEE and DPO-enabled CSSPs are designed for the smartphone and tablet markets, they meet the required size, cost, and power consumption targets that OEMs and system designers require.
Software
As part of the CSSP development process, QuickLogic also provides software and even firmware for our customers.
As an example of this, QuickLogic has developed three distinct software pieces to implement a VEE and DPO-embedded CSSP into the Android OS. They are veeapp.apk, settings.apk, and the Mobile Device Display Optimizer (also known as QlAutoAl.apk).
VEEApp.apk
VEEApp is a Linux application with two modes: command line and daemon. It sits within the library level of Android, above the kernel level. VEEApp communicates with the Android Power Manager to get updated ambient light and display backlight levels and communicates with the QuickLogic VX chip to correctly operate VEE and DPO. VEEApp is programmed to the customer’s unique system by QuickLogic, and requires no development work on the part of the system designer.
Settings.apk
The settings.apk file offers run-time control of display brightness and visual enhancement. The settings.apk file is where the VEE and DPO calibration tables are stored.
Mobile Device Display Optimizer
QuickLogic’s Mobile Device Display Optimizer (MDDO, or QlAutoAl.apk) is an Android application designed to replace the standard Auto Brightness window within Android in systems with a QuickLogic CSSP featuring VEE and DPO.
How VEE and DPO Operate
VEE and DPO are contained within a QuickLogic CSSP chip. The actual operation of VEE and DPO is detailed below.
- The ambient light condition is determined through an Ambient Light Sensor (ALS)
- Upon start up, the CSSP requests the ambient light value. Android reports all ongoing changes in ambient light to the CSSP through QuickLogic software daemon that communicates to Android APIs
- Alternative method: The CSSP can communicate directly with the ambient light sensor through I2C to determine ambient light level. Polling of ambient light data can be programmed at any interval on the CSSP
- Display backlight levels
- Upon start up, the CSSP requests the display backlight level. Android reports all changes to display backlight level to the CSSP through QuickLogic software daemon that communicates to Android power manager where ambient light / display backlight tables are typically stored
- Alternative method: backlight is modulated by instruction of the CSSP through the existing processor or Super I/O chip via a PWM, or the CSSP drives directly it on-board PWM.
- Veeapp daemon determines optimum VEE strength and display backlight level for ambient light conditions by use of calibration table
- The calibration table is created during product development by OEM and QuickLogic. One calibration table is completed and is appropriate for all systems built with the same bill of materials (same display, ALS, and processor)
- Backlight level and VEE strength are adjusted to provide the best possible viewing experience and power savings per the calibration table
- The CSSP can be programmed for immediate changes to backlight/VEE strength with ambient light changes, or for a ‘breathing’ effect for smoother changes
- User adjustments to backlight are accounted for through calibration table—VEE and DPO are fully capable of automatic operation with a standard Auto Brightness curve or manual brightness settings
