The main function of video compression technologies is to reduce and remove redundant data (i.e. no motion and no change in scenery) in video so it can be effectively stored or sent over a network. Modern efficient compression techniques can achieve a significant reduction in file size without sacrificing video quality.
Video compression technologies are commonly known as codecs. They use an algorithm called an encoder that compresses data at the source (i.e. before storage or transmission). At the destination, they use another algorithm called a decoder to decode and decompress the data. Codecs are used in pairs and are not cross compatible. A video encoded using MPEG4 technology cannot be decoded using a H264 decoder.
There are three standard compression technologies used in digital video recorders and IP cameras:
Motion JPEG or M-JPEG is a video compression format based on the popular JPEG compression used for still images. It forms a video sequence and gives the impression of motion by combining several still JPEG images.
MJPEG is a robust video compression format. Since each frame of video is independent, even if one is dropped, the rest of the video is unaffected. This robustness however also translates to higher bandwidth requirements and higher storage space used.
MPEG4 compression technology in video surveillance refers to MPEG4 Visual. Unlike M-JPEG, MPEG4 is a licensed standard. DVRs, IP cameras and other surveillance products must pay a license fee for each channel of video that uses MPEG4 technology.
In terms of compression, MPEG4 supports low bandwidth applications that require decent quality images. It uses video compression techniques to locate redundant data in video and reduce its size.
H264 also known as MPEG4 Part 10/AVC (Advanced video coding) is the latest MPEG standard for video encoding. As of 2010, it is the preferred video encoding standard since it can compress video significantly without compromising video quality. It provides up to 80% reduction in file size compared to M-JPEG and up to 50% reduction compared to MPEG4.
H264 is jointly defined by two standardization groups, the ITU-T’s Video Coding Experts Group from the telecommunications sector and the ISO/IEC Moving Picture Experts Group from the IT sector. Because of this backing, it is expected that H264 will surpass the other standards in terms of adoption.