MOST150 Around View Monitor on a Mainstream Automotive Infotainment Processor
The traditional AVM system uses a dedicated ECU for two reasons:
- The AVM system needs a lot of computing power because it has to perform continuous video processing on four video channels. The video frame rate is about 25~30 fps, in order to prevent loss of frame, and a dedicated ECU is a simple solution to achieve it.
- The AVM system (4 wide-angle cameras plus dedicated ECU) is expensive and mainly installed in high end vehicles. An AVM ECU can output video signals to the display panel of a head unit. For this kind of ECU modular design, the AVM ECU can be easily connected to an existing head unit as an external video input. However, this comes at a cost and hinders the popularization of AVM systems.
Inside AVM ECU, the main video processing unit may be a video grade DSP or a high speed general purpose SoC. Both of them need lots of RAM to store multiple video frames and ROM to store the AVM binary program. The interface to the 4 cameras is also important. An interface to 4 analog composite cameras needs 4 individual video decoders that convert analog video signals to digital domain signals. An interface to 4 digital uncompressed video cameras (LVDS etc.) needs 4 individual digital high speed receivers. Between 4 channels of digitalized video signals and the video processing unit, there might be a video multiplexer that can put all 4 videos signals into one interface that video processing unit can retrieve from. These above components make up the AVM ECU with a high Bill of Material (BOM).
At the same time, the evolution of head units has sped up dramatically. The requests for true color, fancy user interfaces, 3D Navigation and 1080p video decoding and multiple displays for Rear Seat Entertainment (RSE) have forced chip vendors to design more powerful automotive grade infotainment processors. Benefiting from the fast evolution of embedded SoC for smart phone and tablet, the development of new infotainment processors can also keep up with the trend. For example, inside an infotainment processor there is:
- multi-core high speed CPU
- powerful hardware Video codec engine (VPU)
- 3D Graphic Engine with OPENGL ES support (GPU)
With such powerful mainstream automotive infotainment processors, we can leverage the technology by developing more value-added software functions. Examples such as built-in WIFI, internet access and smart phone connection have become mainstream features for car manufacturers.
After evaluating the infotainment processor architecture, we found that AVM video processing functions could also be accomplished by the infotainment processor inside the head unit. Therefore we began development, from the analog camera AVM system which coexists with infotainment functions and executes simultaneously on the same processor.
However, analog cameras can’t achieve high resolution and are vulnerable to car noise. Therefore, a step forward to digital high definition camera AVM on the head unit is more attractive. AVM with higher video quality and less noise inference on a high resolution display is always welcome.
Quanta Storage Inc. (QSI) has designed a multi-purpose platform (Figure 1) for the development of head unit MOST150 camera AVM and MOST50 Rear Seat Entertainment (RSE).
Fig1. Architecture of Multi-Purpose Platform
MOST150 Cameras
4 MOST150 Cameras, all built with wide angle lenses, provide the video sources for AVM. Each MOST 150 camera can be powered by coaxial cable, and the same cable also transmits low latency and high-definition I-frame-only H.264 compressed video. The only connection is coaxial cable, which is easy to install and reduces the need for extra power and ground cables.
MOST150 Interface Board
QSI designed a multiple coaxial interface board that can support multiple MOST150 devices/cameras in a star topology instead of the original MOST150 ring configuration. That means it eliminates the reliability concern that ring topology is not suitable for ADAS applications. This board will also provide power and receive video streams from the same cable. Furthermore, the board acts as the bridge between the infotainment processor and MOST150 cameras.
MOST50 Rear Seat Entertainment
Besides MOST150 AVM development on this platform, we have also developed MOST50 Rear Seat Entertainment (RSE) for VAN/MPV and Luxury Sedan. The MOST50 RSE connects with the head unit or other MOST50 RSE via the MOST50 UTP network. It gets the audio and video from the head unit and display on the LCD panel. Users can also operate the buttons/touch panel and RSE will send these control commands to the head unit, which is capable of multiple display interaction. That means no infotainment processor is needed in RSE. With this configuration, future system upgrades are simplified by only upgrading the head unit itself, prolonging the life cycle of RSE unit. For example, rear seat passengers can view their cloud contents on MOST50 RSE via head unit 3G/LTE or smart phone connection.
MOST50 Interface Board
The MOST50 interface Board can send multiple audio and video channels into the MOST50 network. Each video channel needs a video encoder to encode the uncompressed digital video signal generated from the infotainment processor. The compressed video then feeds into MOST50 UTP networks for the MOST50 RSE display.
Besides audio and video transmission, it can also access data from the MOST50 network, which can extend applications like dual head unit architecture.
Multi-Purpose Head Unit
With a single mainstream automotive infotainment processor in the head unit, the new platform allows both MOST150/MOST50 Interface Boards to run at the same time.
For MOST150 AVM function, the infotainment processor has to decode 4 channels of 720p H.264 video streams from MOST150 networks. Each decoded digital video has to do fish-eye correction, view angle matrix transformation and stitch all 4 videos, then output to LCD display for users to view the AVM video.
Besides consolidating the AVM and RSE functions, the multi-purpose head unit also includes MirrorLink, MiraCast, Apple iOS device link and more of the latest popular technology via USB and WIFI modules.
MOST150 AVM Development Result:
The latency is less than 100ms between real objects and the images shown on the AVM display. The CPU performance is less than 15 percent for MOST150 AVM when using a 4-core Infotainment processor. With its MOST150 AVM low resource requirement, it allows 3D Navigation, multiple fancy UI and audio playback to run simultaneously on MOST150 AVM.
MOST50 RSE Development Result:
The system can show different 3D fancy UI on 4 displays. And with the help of hardware video codecs in the infotainment processor, it can play back multiple 1080p video files. In today’s ever demanding automotive infotainment market, such a setup (HU+2RSE), has become the new trend and will be widely adopted by manufacturers.
As the result, that means we can reuse the same hardware/software platform to implement the MOST150 AVM infotainment head unit system along with MOST50 RSE support. We can also enhance the system further by integrating Audio/Video/Navigation etc. The multi-purpose platform not only provides a low cost factor, robust connection and high extendibility, it also simplifies the overall system structure by reducing the number of ECUs within a car.
About the author: Wen-Jing Li is software manager of Automotive Business Unit at Quanta Storage Inc. (QSI) Taiwan. He has designed and developed car infotainment and ADAS integrated system architecture. Dino.Lin@qsitw.com.
Article previously published in Elektronik automotive, MOST Special Edition, May 2014, www.elektroniknet.de
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