H.263
H.263 is a video compression standard originally designed as a low-bit-rate compressed format for videotelephony. It was standardized by the ITU-T Video Coding Experts Group (VCEG) in a project ending in 1995/1996. It is a member of the H.26x family of video coding standards in the domain of the ITU-T.
| Video coding for low bit rate communication | |
| Status | In force |
|---|---|
| First published | 20 March 1996 |
| Latest version | 3rd edition 24 June 2005 |
| Organization | ITU-T |
| Committee | VCEG |
| Base standards | H.261, H.262 (aka MPEG-2), MPEG-1 |
| Related standards | H.264, H.265, H.266, H.323, H.324 |
| Domain | Video compression |
| License | RAND |
| Website | www.itu.int/rec/T-REC-H.263 |
Like the previous H.26x standards, H.263 is a block-based hybrid video coding scheme using 16×16 macroblocks of YCbCr color sample arrays, motion-compensated prediction, an 8×8 discrete cosine transform for prediction differences, zig-zag scanning of transform coefficients, scalar quantization, run-length transform coefficient symbols, and variable-length coding (basically like Huffman coding but with structured coding tables). The first (1995) version of H.263 included some optional features including overlapped block motion compensation and variable block-size motion compensation, and the spec was later extended to add various additional enhanced features in 1998 and 2000. Smaller additions were also made in 1997 and 2001, and a unified edition was produced in 2005.