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.

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H.263
Video coding for low bit rate communication
StatusIn force
First published20 March 1996 (1996-03-20)
Latest version3rd edition
24 June 2005 (2005-06-24)
OrganizationITU-T
CommitteeVCEG
Base standardsH.261, H.262 (aka MPEG-2), MPEG-1
Related standardsH.264, H.265, H.266, H.323, H.324
DomainVideo compression
LicenseRAND[1][2]
Websitewww.itu.int/rec/T-REC-H.263
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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).[3] 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.