Video Standards

The display of pictures as a video requires more than 15 pictures per second in order to be perceived as a film by the human eye. Concerning the colour information, each pixel needs 24 bit. Compression algorithms utilise the correlations of the pixels inside a picture as well as in between consecutive pictures. Due to compression, spacial and temporal redundancies can be taken in advantage.

H.261

H.261 was the first digital standard for the codification of motion pictures and was adopted in 1988 by the ITU.
This standard forms the basis to run video conferences through ISDN-lines. The necessary reduction of image data for the low bandwidth is implemented by means of the DPCM technique.
The maximum delay for compression and decompression is defined with 150 ms. Beside some other mechanisms a prediction model is used for the following sequence of pictures by Intra-frames and Predicted-frames.

H.262

H.262 is a different term for MPEG-2 Part 3. It defines a video codec that is primarly used for the codification of DVDs and is normally not applied in video conferences.

H.263

H.263 is a ITU-standard which is used for video coding. It's a further development of H.261 whereby its compression rate has been improved significantly.
H.263 was optimised for a low data transmission rate and sequences with relatively low motion.
It was further adopted in MPEG-4 Part 2.

H.264

H.264 is a video compression algorithm which has been developed together with MPEG. The standard here, identical in wording, is called MPEG-4/AVC and corresponds to MPEG-4 part 10.
H.264 is based on its ITU-predecessors (H.261, H.263) as well as on the MPEG-predecessors (MPEG-1, MPEG-2). Compared to H.263, in video conferences with the same image quality the significant development leads to a data reduction by half.

H.265

H.265 is a different term for Standard High Efficiency Video Coding (HEVC). It has been jointly developed by the Moving Picture Experts Group (MPEG) and the International Telecommunication Union (ITU).
Compared to H.264, it has twice as strong compression without any loss of quality and is able to display picture sizes between 320x240 and 8192x4320.