About Systems

A: DVR is functioned as an mage Compression Machine?which processes and squeezes the images and saves them into hard disk. In fact, image compression is complicated and need mass-data mathematics. It is the core-technology of DVR. The major difference differences between PC-Based and Stand-Alone Digital Video Recorders (DVR) is on the ability to add and extend channels. On a Stand-Alone DVR the channels are set and can be added. But on a PC-Based DVR, channels can be added at any time as needed. For example, if an 8 channel Stand-Alone DVR is purchased, that means the maximum number of cameras that can be connected to this DVR is 8. On the other hand, if a PC-Based DVR system was purchased, the channels can be added on later to a maximum of 32 channels.

A: Broadly speaking, surveillance systems can be categorized as standalone type or networked type. For the standalone type of surveillance system, recording is done on a standalone DVR and playback is via a TV. For the networked type of surveillance system, the DVR has network capabilities that allow remote monitoring over the Internet. For some networked surveillance system, recording is done separately on a PC.  For hassle free all-in-one CCTV without need for drilling & hacking walls, take a look at Memo Cam.

A: The biggest advantage of a DVR is transferring analog image to digital and saving it to Hard Disk. Accordingly, compression method will be the key role of improving transmission as well as reducing memory size. Of the various formats, JPEG and MPEG is the most widely used in the market place. The major difference between JPEG and MPEG is in compression techniques. JPEG processes images by compressing one by one still picture but MJPEG compresses image sequence by sequence.

JPEG compress method can be divided into JPEG, M-JPEG, and Wavelet; several formats.

MPEG compress method can be divided into H.263, MPEG, MPEG-II, and MPEG-IV.

A: All video signals transmitted from Network Cameras and Servers must be compressed, transmitted and then decompressed. There are two primary standards for video compression:

MJPEG (Motion JPEG). In this format the video stream is sent as a series of still images (frames), rather like a traditional cartoon. The compression takes place within each individual frame. Each individual frame is a standalone JPEG image which can easily be used for evidential purposes. MJPEG makes it relatively easy to view live images in a fast frame-rate and to record them at a lower rate. Most network Cameras and Servers offer MJPEG compression.

MPEG-4. Many network cameras offer this compression method as well as MJPEG, a few offer just MPEG-4. MPEG-4 compression offers much more efficient use of bandwidth and can be used for multi-casting. However, the compression takes place between frames, ie just taking account of the changes from one frame to the next. This offers better viewing at lower bandwidth utilization, but is not recommended for security applications because a still image can be difficult to verify for evidential purposes.

H.264 is a new compression method similar to MPEG-4 but with even better compression. This is used in a few network cameras, but viewing platforms for this compression method are limited at the moment.

A: Basically, OS can be divided into two major systems, Windows and Linux. All PC-Based DVR and parts of Stand Alone DVR rely on an Operating System to function. Frankly speaking, they provide End Users more functions and software to utilize than Non-OS DVRs. On the other hand, Non-OS DVRs appear a bit more stable than OS DVRs, since all software of Non-OS system are designed only for its self use.

A: Traditional (sometimes called analogue) CCTV systems generally operate on coaxial cables with a single video signal on each cable. These analogue signals are normally recorded onto VHS tape, or more recently onto hard-disk based Digital Video Recorders (DVR). Network CCTV system use standard Ethernet network protocols to transmit digital video streams around the network, where they can be recorded on PC-based or Embedded Systems.

A: Network Video Servers take the analogue video signals from standard CCTV cameras and re-transmit them onto the local area network in the same way as a network camera.
They are used in a number of circumstances, for example, to integrate an existing analogue system into a networked system or to enable specialized non-network cameras to be used.
Camera supplies Network Video Servers in 1, 2 & 4 channel configurations. We also supply Video Servers with digital recording capability.

Wireless Network Cameras operate on the IEEE Ethernet 802.11b/g standard and are compatible with all wireless routers and access points which meet these standards. The theoretical maximum distance for wireless transmission is several hundred meters, but in practical terms this distance is significantly reduced if there are obstructions, e.g. walls, in the way. Wireless connections are suitable for indoor, short-distance transmission, but require additional equipment, e.g. outdoor antennas, for other installations. In many installations finding a suitable mains power point can be as difficult as putting in a network cable. We often find that Power Over Ethernet is a better alternative to wireless.