![]() A megabyte is used to measure file size.A megabit is used to measure download and upload speeds.Here are the bare essentials of what you should know: ![]() Understanding Mbps helps you make an informed decision when shopping for internet service and for calculating what speed you need based on your typical uses. Internet speeds usually get advertised in megabits per second (Mbps), so it pays to know what the term means and how much data one megabit contains. Remember, video stream quality and data bandwidth are directly correlated but, a customer does not need to provision for balance-sheet breaking data pipes in order to view good resolution surveillance video streams.The difference in speed scales is mainly technical, but it has a bearing when making broadband buying decisions. The quality of the video stream may not be the best but, the viewer gets a live video stream from all the cameras at the site under surveillance. Doing the math returns a figure of 292.571 in turn, pointing the viewer to a bit rate of 256 Kbps. ![]() If the quality of the connection, for a given bandwidth, is poor the likelihood of dropped frames is high, and the playback frame rate may be lesser than the recorded frame rate (resulting in poor video quality).Īnother way of working out which bit-rate to go with, is to take the bandwidth available, between the site where the cameras are located and the remote user, (let’s say 2 Mbps) and divide it by the number of surveillance cameras at the site (let’s say 7). There is a caveat to this statement, though. A process of trial and error, though, soon establishes that the improvement in the quality of the video stream does not improve significantly (apparent to the human eye) above a certain bit-rate (in the case of the Mistral Smartvue cameras, 1.5 Mbps).So, if video stream quality is important, but bandwidth is at a premium, this is the bit-rate to go with. ![]() Ideally, a remote viewer would like to settle for the highest bit-rate however, we don’t live in an ideal world (unless the viewer has an 100 Mbps Ethernet pipeline to its location). InsightServer2, from Mistral Smartvue, offers the following Bit-Rate options: Typically, video management applications allow the viewer to select the bit rate s/he would like to apply for the video stream, from the surveillance camera. The compressed bandwidth requirement, using the above mentioned video compression standards, looks something like the figures given in the table below. Let’s now apply video compression to the raw data bandwidth calculated above. The higher the compression, the greater the possibility of the presence of compression artefacts (frame break-up, blockiness, etc.) in the reconstituted image. The higher the Bit Rate, the better the quality of the video stream. The level of compression possible is dependent on the video quality acceptable to the viewer with a Bit-Rate figure encapsulating the bandwidth requirement for a given quality of video stream. We will not go into the details of each standard, except to state that bandwidth reduction of anywhere between 80 – 99.5% is possible through the use of video compression.Īll video compression standards work on the Constant Bit Rate (CBR) process, with minor variations. The popular video compression standards are MJPEG, MPEG4, and H.264 (also referred to as MPEG4-AVC). It is huge and, it represents the bandwidth requirement of just one content generating source (a surveillance camera, in this case).Īlong comes video compression, and the bandwidth requirement starts getting manageable. This is the raw data bandwidth requirement. 720 x 480, and transmitting at 30 fps (frames per second) the relevant numbers add up as follows: ![]() If we take a camera capturing an image at D1 (DVD) resolution, viz. Bit Rate = Frame Size * Frame Rate (fps).Frame Size = Resolution * Colour Depth (Chrominance/Luminance information).There are additional factors such as audio bandwidth and protocol (communication and compression) overheads but, these do not add significantly to the bandwidth. One question in the minds of many users and potential users of video surveillance is, How do I calculate the quantum of data generated by a surveillance camera and what is the bandwidth required to stream live video stream to remote viewers?Ĭalculating the approximate bandwidth of a video stream is a matter of multiplying the resolution of the captured image with the number of frames for the moving image. ![]()
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