H.263 - definition
A video codec standard originally designed as a low-bitrate compressed format for videoconferencing. It has been widely adopted as the standard for video streaming over mobile networks.
Standard image sizes specified by H.263 include SQCIF (128 x 96 pixels), QCIF (176 x 144), and CIF (352 x 288) resolutions.
H.263 handles only the visual part of a video stream, the audio is encoded using audio encoders such as AMR.