One other item to keep in mind is that both MPEG-2 and MPEG-4 are subject to licensing fees, which can add additional costs to the maintenance of a network video system. It is important to ask your vendor if the license fees are paid. If not, you will incur additional costs later on.
Another important consideration is the use of proprietary compression. Some vendors don't adhere to a standard 100 percent or use their own techniques. If proprietary compression is used, users will no longer be able to access or view their files should that particular vendor stop supporting that technology.
Proprietary compression also comes into consideration if the surveillance video will potentially be used in court. If so, using industry standard compression ensures that video evidence will be admissible. Some courts believe that evidentiary video should be based on individual frames, not related to each other or manipulated. This would eliminate MPEG because of the way the information is processed. The British court system, which has been leading digital video admissibility, requires an audit trail that describes how the images were obtained, where they were stored, etc., to make sure the information is not tampered with in any way. As digital video becomes more widely adopted, the issue of admissibility in court will be one to watch.
Compression is one of the most important factors to building a successful network video system. It influences image and video quality, latency, cost of the network, storage, and can even determine whether video is court admissible. Because of these considerations, it is important to choose your compression standard carefully ... otherwise, the video may be rendered obsolete for your purposes.
Does one compression standard fit all?
When considering this question and when designing a network video application, the following issues should be addressed:
- What frame rate is required?
- Is the same frame rate needed at all times?
- Is recording/monitoring needed at all times, or only upon motion/event?
- For how long must the video be stored?
- What resolution is required?
- What image quality is required?
- What level of latency (total time for encoding and decoding) is acceptable?
- How robus/secure must the system be?
- What is the available network bandwidth?
- What is the budget for the system?
About the author: As the general manager for Axis Communications, Fredrik Nilsson oversees the company's operations in North America. In this role, he manages all aspects of the business, including sales, marketing, business expansion and finance. He can be reached via email at firstname.lastname@example.org.