Compression: H.261 (px64)

• Videoconferencing following international standards uses this approach, with p from 1 to 30, covering the range of 1 ISDN connection (64 Kbps) up past the capacity of a T-1 link (1.54 Mbps).
• Since this is done in real-time, minimal motion compensation can be achieved.
• The connection has a fixed bandwidth, so buffering is needed to smooth the flow, and when too many bits are used for compressing a complex image, the quantization quality is reduced to compensate thereafter. A feedback control adaptively adjusts to these changes.
• DCT and Huffman coding are used as in MPEG.
• H.261 was updated later by H.320.