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Case study: MOST150 AVM on car infotainment processor

Posted: 09 Dec 2014     Print Version  Bookmark and Share

Keywords:Around View Monitor  AVM  ADAS  ECU  MOST50 

Around View Monitor (AVM) is a popular application among Advanced Driver Assistance Systems (ADAS). The AVM system converts video recorded by four cameras, which are mounted in the car, into a top view video. The driver can have a better viewing angle of the surrounding objects. Hence, with the help of AVM, drivers will feel more comfortable when parking the car or driving through a narrow alley.

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 popularisation 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 analogue composite cameras needs 4 individual video decoders that convert analogue 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 digitalised 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 colour, 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 analogue camera AVM system which coexists with infotainment functions and executes simultaneously on the same processor.

However, analogue 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.

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