Video Compression and Data Flow for Video Surveillance Whitepaper

Executive Summary The desire for increased security has catapulted the popularity of video surveillance systems, which are now widely deployed in places such as airports, banks, public transportation centers and even private homes. The many problems associated with traditional analog-based systems are influencing the push for digital-based systems. Furthermore, with the growing popularity of computer network, semiconductor and video compression technologies, next-generation video surveillance systems will undoubtedly be digital and based on standard technologies and IP networking. This paper discusses how to overcome the constraints of a limited network bandwidth with motion estimation (ME) and motion JPEG techniques. In addition, the paper will explore how DSP exercises video codecs for better performance. In a video surveillance system over Internet Protocol (VSIP), hardware handling the network traffic is an integral part of the camera. This is because video signals are digitalized by the camera and compressed before being transmitted to the video server to overcome the bandwidth limitation of the network. A heterogeneous processor architecture, such as digital signal processor (DSP)/general purpose processor (GPP), is desirable to achieve maximum system performance. Interruptintensive tasks such as video capturing, storing and streaming can be partitioned to GPP while the MIPS-intensive video compression is implemented on the DSP. After the data is transferred to the video server, the server then stores the compressed video streams as files to a hard disk, overcoming traditional quality degradation associated with analog storage devices. Various standards have been developed for compression of digital video signals, which can be classified into two categories: • Motion estimation (ME)-based approaches – N frames are defined as a group of pictures (GOP) in which the first frame is encoded independently. For the other (N–1) frames, only the difference between the previously encoded frame(s) (reference frame(s)) and itself is encoded. Typical standards are MPEG-2, MPEG-4, H.263 and H.264. • Still image compression – Each video frame is encoded independently as a still image. The most well-known standard is the JPEG. MJPEG standard encodes each frame using the JPEG algorithm.