IP Camera Protocols: PSIA ONVIF CGI ISAPI

Based on HIS Markit research and investigation, over 66 million network cameras will be shipped globally, greatly outpace the shipment of HD CCTV cameras (28 million). Although the growth becomes slower than past years due to the global gloomy economy and the aggressive price competition, the market research company forecasts that the world market for video surveillance will grow by over 7% in 2016. 

Apparently, the maturing network camera standard and protocols make a great contribution to the fast development and market growth of IP surveillance products. PSIA and ONVIF are two major standards/protocols that universally adopted by IP surveillance products. On one hand, these standards has reduced the cost and complexity of IP video surveillance, also solved the interoperatability between different network devices.

Back to 2009, Ajit Dubey, senior project manager of the Embedded System Group wrote that Interoperability was a key challenge for security professionals managing PTZ, network configuration and legacy compatibility. While IP provided the benefits of connectivity, wider uptake faced a number of challenges. Manufacturers had a selection of video coding standards, which each had different profiles. There was more fragmentation in streaming protocols, storage formats and video analytics. Configuring PTZ functionality was also difficult between third-party video devices. 

1#. What’s PSIA?

PSIA, its full name is Physical Security Interoperability Alliance, it was formed in 2008 with mission to create standards-based interfaces for physical security hardware and software platforms. The alliance pursue the goal of bringing interoperability to network based security systems. This alliance has more than 50 physical security manufacturers and system integrator such as Honywell, Tyco, United Technologies, Milestone, Allegion etc. 

2#. What’s ONVIF?

ONVIF also founed in 2008, ONVIF is the abbreviation of open network video interface forum, it’s an open organization led by Sony, Axis, Bosch. After 8 years development, the ONVIF becomes the universal standard intending to solve the connection and interopratebility problems between different IP based security products. The organization currently has Profile S, Profile C, Profile G, Profile Q etc different specifications dedicated to different applications. More than 1000 manufacturers joined the ONVIF membership. 

As we previously mentioned, PSIA and ONVIF are main standards being used by different IP security products. However, ONVIF owns the largest group of manufacturers, there are millions products are compliant with ONVIF products, among them about 5000 products are certified by ONVIF. It seems PSIA will be phased out because lacking the support by manufacturers. However, some companies such as Hikvision providing the products are compliant with both ONVIF and PSIA standards. 

3#. What’s difference between PSIA and ONVIF?

Since both standards share the same mission and goal.  Not only manufacturers and integrator seem to be suffering from indecision, many users don’t know the difference between them.

According to the article written by Ajit Dubey, PSIA had defined specifications which were more general for the broader physical security market including access control, storage and more. While the ONVIF seems to concentrate on IP video streaming, particularly network cameras and video analytics. So, the ONVIF made the specification intending to solve the interface problem of video stream transceiver. The specification criteria includes device discovery, device configuration, events, PTZ control, video analytics, push notification and video streaming etc functions.

Ajit Dubey also listed the technology differences between ONVIF and PSIA, which may drive the adoption of standards in the IP surveillance market.

1. PSIA uses the representational state transfer (REST) architecture. On the other side, the ONVIF specification is built upon open platform web service standards such as XML (for data description syntax), Simple Object Access Protocol (SOAP, SOAP 1.2) to transfer message and WSDL to describe the services. Almost all Web services are using REST today, it’s simple to use compared to SOAP and only requires less overhead than SOAP. 

2. ONVIF can provide 100-percent interoperability between compliant products as far as device discovery is concerned, this dues to using the Microsoft-centric technology (WS Discovery) for its device discovery mechanism. This means all ONVIF compliant network devices must adopt the WS Discovery method. 

PSIA offers several different mechanisms for device discovery, including Bonjour, uPnP, Zeroconf . While PSIA provides more flexibility to adopt mechanisms for device discovery, However, this also leads to complexity in interoperability for connecting PSIA-compliant products. E.g, a PSIA-compliant camera supporting Bonjour cannot be connected with a PSIA-compliant video management system supporting UPnP, despite both the camera and video management system being PSIA-compliant. 

3. PSIA can not provide 100 percent interoperability for PSIA specifications compared to ONVIF specifications. The reason is PSIA uses generalized message format for event and notifications, while the ONVIF’s event notification is based on the WS-Notify framework.

4. PSIA provides an easy interface for analytics integration compared to rigid ONVIF specifications.

5. Due to its REST-based architecture, PSIA's implementation is lightweight compared to ONVIF's SOAP-based architecture implementation.

4#. What's CGI and ISAPI?

Except above mentioned two main standards, some manufacturers produce the IP cameras support CGI and ISAPI. Both CGI and ISAPI are used for web development. CGI, that's common gateway interface typically runs on Linux OS, it's a script running on server to interact with client's HTML webpage. CGI is the one of important WWW technologies, it performs as a bridge to link the application program (CGI program) and web server. It's also a specification to transfer messages between program and web server. By contrast, ISAPI is an N-tier API of Internet Information Services (IIS) runs on Windows OS. The ISAPI is the abbreviation of Internet Server Application Programming Interface.

When using the CGI protocol, the users can type the commands: http://{ipaddress}:{port)/snapshot.cgi?user=admin&pwd=password to config the snapshot setting. Typically, the IP camera manufacturers will provide users a document to list all the CGI commands that the IP camera can support. Other network cameras may support the ISAPI, users can use the commands such as http://{ipaddress}:{port)/snapshoot.exe?user=admin&pwd=password or http://{ipaddress}:{port)/snapshoot.dll?user=admin&pwd=password to access the camera's snapshot setting. 

Obviously, by using the CGI and ISAPI, the camera can provide much more flexibility to users, especially when they want to achieve certain function based on their exclusive requirement or integrate the camera to different security systems.

5#. What's GB/T28181 standard?

Chinese government (Ministry of Public Security) released the GB/T28181 standard to the video surveillance market with purpose to solve the monopoly of ONVIF. GB/T28181 is the code name for the <security video surveillance network system of information transmission , switching, control technology requirements>, it's released dated back to 2012. Many Chinese network video surveillance products support GB/T28181 standard along with ONVIF. Since it's a national standard to Chinese products, unlikely this standard will be adopted globally.