Digital Video Interface (DVI) has been designed as a replacement for VGA (analog interface). However, in some cases DVI still supports analog displays. In fact, DVI is the only standard which can carry both analog and digital signals on one interface. If the display is analog, the DVI connection will convert the digital signal to an analog signal, otherwise no conversion will be necessary. It is worth mentioning that, the analog video bandwidth of DVI is higher than VGA, thus higher resolution can be supported compared to VGA. So, it can be applied by high resolution displays such as UXGA and HDTV.

DVI cables or ports with fewer pins are designed for lower resolution devices. In order to support maximum resolution, the DVI port should contain all the pins. Since DVI does not support High-bandwidth Digital Content Protection (HDCP) encryption by default, by using hardware which only includes DVI ports, the video protection is not guaranteed. This is the biggest drawback of DVI. Since HDCP protects video from illegal copying, this feature is very critical for video surveillance systems. KickAss Torrents

Without any form of compression in video streaming, the network can't transmit the raw data. Also, due to large file sizes, storing data on limited capacity of disk drives is not possible. That's why we need to use compression, especially in video surveillance systems. Video compression removes redundant video data, so that the video file can be transmitted or stored effectively. Video content is encoded and decoded by using a video codec method, inside a container format, so the video quality is not degraded at the time of transferring over the network. We study the concept and some different types of video codecs and video containers along with their differences.

What is video codec?

A codec is a software used to compress or decompress a digital media file for transmission over a data network. In fact, a pair of encoding and decoding algorithms that work together is called a video codec, so that encoder uses these algorithms to effectively compress the size of the video file, and then decoder decompress it when needed. Some codecs include both of these components and others include one of them. Moreover, codecs are divided into two categories: lossless and lossy codec. In lossless codec all the information is kept in the original stream, thus the video quality is preserved. On the other hand, in lossy codec due to using lower data bandwidth and missing some of the original data to achieve the best compression, the quality will be reduced.

There are different standards of codec which use different technologies to encode and decode the video file related to intended application. Since video content that is compressed using one standard cannot be decompressed with other standard, different implementation of video codecs are normally not compatible with each other. Because, one algorithm cannot correctly decode the output from another algorithm.

However, implementing many different algorithms in the same software or hardware is possible, so multiple formats can be compressed. Utilizing different methods of compressing data leads to variant bitrate, quality and latency. The time it takes to compress, send, decompress and display a file, called latency.

How video compression can help video surveillance?

Video compression methods use a codec to reduce or eliminate unnecessary files or frames from video files, without any significant degradation in final video. This makes the video file smaller, so more video can be stored on NVR hard drives or files can be kept for longer periods of time.