What is H.263?
H.263 is one of the traditional video compression standards. It was initially designed specifically for video telephony as a standard that uses low bitrates for compressing various files.
H.263 was initially standardized as early as 1995/1996 by the ITU-T Video Coding Experts Group (VCEG). The H.263 belongs to a long line of video standards of the H.26x class.
History of H.263
The H.263 standard is based on the previous H.26x variants because it is also a block-based hybrid video encoding algorithm.
The initial version, launched in 1995, included additional features like overlapped block motion compensation. More features were added in 1998 and 2000 until the final, unified version of the standard was released in 2005.
H.263 vs. H.262 & H.261
- H.263 is an evolved version of the traditional H.261 and H.262 algorithms.
- The primary difference is that H.263 uses low bitrates compared to the previous H.261 and H.262 standards.
- Many design features like the DCT (short for Discrete Cosine Transform) and the use of intra-frames and predictive coding for inter-frames.
- It also offers improvement in smoothening compressed blocks to avoid inconsistencies upon decompression during playback.
- Another unique feature in H.263 but not in the previous standards is the inclusion of the B frame.
- H.262 and H.261 used the I and P frames for compression.
- H.263 also uses the revolutionary B or Bi-Directional frame, a technology that can precisely predict the position of an object by analyzing the past and future frames.
- B-frames are more efficient because they have greater availability of options based on how data can be compressed temporally and spatially.
- B-frames, however, are resource-heavy and might lead to slower speeds.