Driving The Future Of Automotive Displays With Video Compression

Mobile devices have heavily influenced the demand for displays in all areas of our lives over the last decade, and one area where there has been a particularly rapid transformation is in cars. This article will look at some of display trends in cars and investigate how VESA (Video Electronics Standards Association) video compression codecs can be leveraged by automotive designers to meet these trends.

Looking at some of the innovative car designs from leading automotive manufacturers at CES (Consumer Electronics Show) this year, we can see that displays are a key element of next-generation cars and are set to get even bigger and even more sophisticated in the years to come. BMW, for example, previewed its future in-car entertainment system known as the “BMW Theatre Screen”; it features a massive 31-inch 8K resolution screen (7680 × 2160 pixels) with built-in 5G connectivity. It is nothing short of a full cinematic experience all from the back seat of a car!

While most of us have not yet had the chance to experience something like this, we have all become accustomed to having more displays in our cars, and not just for entertainment. A driver instrument cluster display, a center console display, and even a co-driver display are common car features these days. Not only has the number of displays inside cars been growing, but these displays have been getting bigger and bigger with each new generation of cars, and consequently so too have their display resolutions.

There is also a growing trend towards replacing mirrors with displays. For example, in some cars the rear-view mirror has been replaced by a display connected to a rear camera. Substituting the traditional rear-view mirror with a display system has many advantages. It can provide a wider viewing angle, and the rear view cannot be obstructed by passengers, or any object carried in the vehicle. In addition, critical safety information, such as the distance between the vehicles or obstacles behind, can be added as an overlay on the display.

All these displays result in a huge increase in the total amount of display bandwidth inside cars. Implementing video connectivity in cars is challenging because all the displays and their display connections need to meet strict Electro-Magnetic Compatibility (EMC) requirements and they cannot be too power hungry, something which is even more important for electric vehicles. What is more, when used for safety critical ADAS (advanced driver assistance systems), such as pedestrian detection or lane departure warnings, displays need to support functional safety according to the ISO 26262 standard and Automotive Safety Integrity Level (ASIL) classifications.

So why not simply add extra cables to drive all these displays? More cables are not the answer for automotive manufacturers as more cabling adds to the weight and cost of a car’s wiring harness, one of the heaviest and most expensive components of a vehicle.

Given their low latency, low footprint, and visually lossless performance, DSC (Display Stream Compression) and VDC-M (VESA Display Compression) are excellent candidates for automotive manufacturers integrating more, larger, and higher-performance displays. Video compression can reduce the number of cables needed as it allows more video streams to be carried over a single display link. Compression can also reduce power and solve EMI (Electro Magnetic Interference) challenges, as each link could be operated at a lower bandwidth. Finally, video compression can enable higher quality displays by allowing High Dynamic Range (HDR) content to be carried with no more bandwidth than Standard Dynamic Range content.

VESA DSC and VDC-M have been adopted into the MIPI DSI-2 display interface specification, one of the most widely used embedded display interfaces for mobile, AR/VR, and now automotive applications. Last year, the MIPI Display Working Group conducted a study to show that VDC-M compression was safe to use for automotive applications. The study was published as a whitepaper and concluded that VDC-M compression was visually lossless for automotive use cases, meaning that the test images compressed at a maximum 6:1 compression ratio were indistinguishable from the same images that had not been compressed.

Rambus offers encoder and decoder IP cores supporting the VESA DSC and VDC-M compression standards, as well as a MIPI DSI-2 controller. These IP solutions are silicon-proven and tailored for use in safety-critical automotive applications.

Additional resources:

• Rambus VESA DSC & VDC-M IP Cores
• Rambus MIPI DSI-2 Controller IP Core