Motion JPEG

Motion JPEG ( MJPEG) is a video codec, in which each frame is separately compressed as a JPEG image.

Overview

The compressed with MJPEG video is not dependent on the movement of the image quality in contrast to the compressed with MPEG. Because of high quality ( at 3.125 MB / s ( 25 Mbit / s) about SVHS quality) of the video and the existing encoder hardware is this standard often used by digital cameras. Through the individual compression of all individual images, it is possible with this format to cut a video clip without the need of Recodierens picture exactly what is only possible with key frames in MPEG in general. There are numerous variants of the format, some of which are not compatible with each other.

For the QuickTime format, Apple has defined two types of coding: MJPEG -A and MJPEG -B. The second version is no longer compatible with the JPEG File Interchange Format - individual images can not be easily converted from the video stream into a JPEG image without changing the information in the header of the file.

The compression rate is 1:5 to 1:13 between uncompressed formats, including RGB / 8 (1-1), or YCbCr / 8 ( 1:1.5 or 1:2 ) and the MPEG-2 compression (about 1: 25 to 1:100). With high quality corresponding to PAL video in about 30 Mbit / s, which is why most digital cameras can record only relatively short sequences.

Application

Server

M -JPEG is applied to IP-Cams, ie network cameras. Here, the stream is often sent over the HTTP protocol. For the client (usually a Web browser) can display the data correctly, the special MIME type multipart / x - mixed-replace is; boundary = used. It follows an arbitrary string for the separation between the individual pictures after the MIME type boundary =. This is followed by the individual JPEG compressed images, separated by the string defined in the MIME type. Example implementations can be found in and.

Clients

Commonly used clients for displaying M -JPEG streams are common web browser such as Firefox. At present, Internet Explorer does not support M -JPEG streams. Solutions exist, such as Java applets for this popular browser. Network Compatible Multimedia player like VLC and MPlayer are also suitable for the representation of an M -JPEG stream. In addition, the game console Nintendo Wii and PlayStation 3 and PlayStation Portable from Sony, as well as the Safari browser of the iPhone by Apple movies in M -JPEG format can play.