GMSL Steps Out of the Car to Enable New Applications for Miniature Surveillance Cameras

by Neal Kurifss and Michael Jackson

The last blog in this series presented some ideas on how security and surveillance camera designs can benefit from the ‘2-in-1’ power and data features offered by industrial Ethernet. This blog explores some new and emerging use cases for miniature surveillance cameras and how they can be realized by exploiting the unique features of Analog Devices’ Gigabit Multimedia Serial Link (GMSL) technology.  

Conventional Security Cameras are Designed to be Noticed

It is perhaps somewhat ironic that while security and surveillance cameras provide users with a means to capture evidence of intruders performing unauthorized acts (trespassing or stealing), they are probably even more useful at deterring people from carrying them out in the first instance. Therefore, to make people aware that their actions are being observed, many cameras are intentionally designed to be bigger than they need to be and installed in locations where they are quickly noticed. While conventional pan-tilt-zoom (PTZ) security cameras typically include a motor to allow them to move (hence broadening their field of view), they can’t provide continuous scene coverage, meaning intruders can bypass them. Using multiple cameras can ensure 100% coverage, but large PTZ cameras require even more space, and this approach is expensive, not only in terms of the cost of the units themselves but also that of installing cabling to provide connectivity and power for the additional cameras. 

Miniaturization Enables New Multi-camera Use Cases for Even Greater Security 

While PTZ security cameras can be conveniently installed in retail premises and offices (which typically have sufficient space), they are often too big to be used in other locations, like elevators, automated teller machines (ATMs), and public transport (rail and buses). Furthermore, large, and noticeable security cameras are considered ‘distasteful’ by retailers of jewelry or other high-end products who want their clients to feel trusted (while still reserving their right to observe and record every movement a customer makes!). Another emerging trend is multiple micro-cameras being installed in smart buildings alongside other utilities like air conditioning, lighting luminaires, and power outlets. 

Figure 1 Micro-camera module installed in the power outlet 

For a combination of practical and aesthetic reasons, these use cases require multiple cameras with miniature form factors and cabling that can simultaneously carry power and transport high-bandwidth video (and even sometimes also the audio feed from accompanying speakers). Ethernet is not a good solution for applications like these because the connectors and cabling it requires are too bulky – for example, an RJ45 jack is comparable to the size of some small cameras.  

Figure 2 An Ethernet RJ45 jack similar in size to some micro camera modules 

GMSL is THE Power and Data Solution for Multi-micro-camera Applications 

GMSL is a data serializer-deserializer (SerDes) technology that was developed to address the high-speed data requirements when using multiple cameras to enhance automobile safety, but its features are also ideal for enabling the use cases previously discussed. These features include:  

• Simultaneous transmission of high-definition (HD) video, audio, and control signals over a single cable - coaxial or single twisted pair (STP) 
• Excellent signal integrity over distances up to 15 meters 

• Real-time link diagnostics, including ‘frozen-frame’ detection 
• Deterministic low latency 
• Power over coaxial cable 

GMSL supports a wide range of video interfaces including CSI-2, DSI, HDMI,eDP, DP, and oLDI. 

Figure 3 GMSL carries power and data between a camera module and an image processor 

Analog Devices recently released next-generation GMSL2 SerDes products – the MAX96717 serializer and MAX96714 quad-deserializer - which use CSI to interface between an image sensor and a processor at data rates up to 6 Gbps, while maintaining backward compatibility with GMSL1 data rates (3 Gbps). 

Table 1 GMSL1 and GMSL2 product-pairs from Analog Devices 

Figure 4: Block diagram of a 4-camera GMSL2 solution

Figure 5 shows a demonstration reference design for a 4-camera GMSL2 solution featuring: 

• Four 7.4MP Sony Cameras running at 4.4Gbps with embedded GMSL2 Serializer 
• ~15m LEONI Dacar 302 Coax cables 
• GMSL2 Quad De-serializer aggregates 4 streams to 17.6Gbps through a 4-trio CPHY port 
• Nvidia Xavier SoC processes RAW images and outputs HDMI 
• Four tiling images with scaled resolutions on a 4K display 

Figure 5: ADI's 4-camera GMSL reference design

With GMSL, camera module data transfer, cabling, and power are simplified, allowing the module electronics and interface to be miniaturized to meet the requirements of new and emerging use cases for security and surveillance camera applications. The next blog in this series will explore augmented vision applications for security and surveillance cameras.