With the rise in popularity of adding MHL or HDMI interfaces to tablets and smartphones, already-overburdened system designs now face another challenge—how to integrate a secondary video output into a system designed to support only the on-board display?
This is a huge challenge, primarily so based on the number of concurrent outputs that CPU’s generally support and the interface support required. Most mobile-centric application processor support MIPI. While some of these also offer additional support for RGB natively, not all of those offer support for both interfaces to output simultaneously. Additionally, while some mobile-centric processors support native HDMI, very few actually support a native MHL output. Embedded pico projectors also generally require an incoming RGB signal.
This presents an issue, given that a system with MHL/HDMI or an embedded pico projector will require two separate, distinct, and concurrent video data flows from the processor. MIPI and RGB data cannot readily be ‘multiplied’, meaning support for this architecture will require either a (more expensive) processor capable of handling simultaneous, distinct outputs, or a device that accepts a single input from the processor and can bridge the interface to at least 1 differing standard.
The ArcticLink III VX6 offers tablet and smartphone system designers a standard way to solve this increasingly common design issue.
|VX6BxE||MIPI||MIPI & RGB|
|VX6BxG||MIPI||LVDS & RGB|
|VX6BxH||MIPI||MIPI & LVDS|
As the table shows, QuickLogic offers multiple options for “duplicating and bridging”, or “bridging and bridging” two separate outputs bridging a single MIPI-DSI path from the processor to MIPI and RGB, LVDS and RGB, or MIPI and LVDS for easy embed of a pico projector or MHL transmitter The VX6 supports display resolutions up to 1920 x 1080 (WUXGA), including popular resolutions such as 720p (1280 x 720), WXGA (1366 x 768), and 1080p (1920 x 1080). MIPI-DSI is offered in 2 and 4 lane variants with per-lane speeds of 1 Gbps, while LVDS is supported in 1 or 2 channel (4 lanes per channel) architectures. The VX6 supports simultaneous single or dual output.
With VEE (left) and without VEE (right)
Displays are the largest single consumer of power in a typical mobile designs. In tablets, large format, high density displays can consume more than 60% of total system power. As the largest consumer of power, displays also represent the largest opportunity for power reduction. While power savings can be had by simply turning down the brightness, doing so reduces the display viewability to a point where most content is un-viewable. There are other ways to reduce brightness (such as Content Adaptive Backlight Control [CABC] or ambient light correction), but these methods are very limited in the maximum power than can be saved; often this is <5% and almost always content-dependent, thus not predictable.
QuickLogic’s VEE and DPO’s approach to display enhancement and power savings is a radical advancement from these legacy technologies.
To best provide display viewability, QuickLogic employs VEE HD+ on the ArcticLink III VX6 devices. VEE HD+ is based on a model of human perception, which is far beyond other, more primitive methods of display enhancement which are based on machine models of perception. VEE’s human perception model insures that display viewing experience is always most pleasing to the viewer. This stands in contrast to alternative technologies which often sacrifice details in certain areas of the display to increase viewability in other areas, with no concern as to what the content of those particular areas are.
To accomplish this, VEE examines performs a pixel-by-pixel, frame-by-frame analysis of display content, and using the human-eyesight approach, determines the ideal tone curve for each pixel of the embedded display. This insures that the viewer experiences the content in a manner most typical of how the eye would expect to see it, rather than how a machine would best want to interpret the video data.
One common usage issue with smartphone and tablets is the inability to view content, especially videos and images, in bright sunlight. Excessive, bright sunlight reduces or eliminates the viewability of portable device displays by reducing the effective contrast ratio of the display. Through its ability to optimize dynamic range and contrast on a pixel-by-pixel, frame-by-frame basis, VEE can offset sunlight’s negative effects on viewability, allowing the viewing of content on a mobile display at a level approaching what would be expecting natively, without the interference of ambient light.
With no processing requirements placed on the host system, the VX6’s VEE HD+ technology presents an ideal solution for providing users the best display experience without taxing system resources.
VEE HD+ can also be applied to the display path of the pico projector, increasing ‘effective lumens’. One of the biggest issues with pico projector mass market adoption is often mis-stated as insufficient lumen output. In reality, lumen’s are a specification widely open to individual interpretation. Users don’t particularly care how bright the image is—they simply want a projected image that is readily viewable without having to turn off all the lights in the room. As this this is not a realistic thing to ask of ever more demanding consumers, QuickLogic’s VX6 with VEE HD+ can be employed to enable much greater effective lumens due to its ability to optimize the projected content for the viewing environment.
While VEE HD+ works to best improve viewability, DPO HD+ works in concert to best conserve power in the system using intelligent manipulation of the embedded displays brightness. DPO HD+ receives information on ambient light level through the device’s on-board ambient light sensor (ALS), and works with VEE HD+ pixel-by-pixel tone curve to lower display brightness without negatively affecting the viewing experience. During the OEM design process, the OEM can choose to implement VEE and DPO based on desires for (1) the best possible viewing experience, (2) the longest-lasting single charge battery life or (3) a determined-mix of power savings and visual enhancement. While DPO HD+ power savings are completely independent of display content (allowing for predictable, consistent savings), VEE and DPO are not used to control external (MHL/HDMI connected) display brightness or viewing enhancement.
OEM-proven systems (see below) using VEE and DPO HD+ have been shown to extend battery life an average of 25%, with OEMs seeing as much as 41% single-charge battery life extensions.
Real World Power Savings
(Actual results depend on implementation)
In addition to DPO HD+, the ArcticLink III VX3 integrates QuickLogic’s Intelligent Brightness Control (IBC) technology, which allows for even greater power savings. When display content is of lower contrast or dynamic range (such as streamed movies from YouTube), display brightness is often needlessly high. When active, IBC examines display data in an effort to further reduce display brightness without affecting the viewing experience. IBC can add up to an additional 10% in system power savings (content-dependent) on top of DPO’s already impressive savings.