ITU-T Recommendation H.263
Title: Video coding for low bit rate communication
Date of adoption: 03/1996
This Recommendation specifies a coded representation that can be used for compressing the moving picture component of audio-visual services at low bit rates. The basic configuration of the video source coding algorithm is based on Recommendation H.261 and is a hybrid of inter-picture prediction to utilize temporal redundancy and transform coding of the remaining signal to reduce spatial redundancy. The source coder can operate on five standardised picture formats: sub-QCIF, QCIF, CIF, 4CIF and 16CIF.
The decoder has motion compensation capability, allowing optional incorporation of this technique in the coder. Half pixel precision is used for the motion compensation, as opposed to Recommendation H.261 where full pixel precision and a loopfilter are used. Variable length coding is used for the symbols to be transmitted.
In addition to the basic video source coding algorithm, four negotiable coding options are included for improved performance: Unrestricted Motion Vectors, Syntax-based Arithmetic Coding, Advanced Prediction and PB-frames. All these options can be used together or separately.