TABLE OF CONTENTS Digital video coding has gone through a long history of technological evolution (see Figure 5.2). The first practical digital video coding standard was H.261, proposed by the International Telecommunication Union (ITU-T) in 1990 [2], originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbps. The coding algorithm was designed to be able to operate at a data rate between 40 kbps and 2 Mbps. The standard supports both CIF (352 288) and QCIF (176 144) video frames with the 4 : 2 : 0 chroma subsampling. Owing to the pioneering effort of H.261 design and collaborative development, all subsequent international video coding standards (MPEG-1, MPEG-2/H.262, H.263, and even H.264) have been following a similar architectural design and standardization process. The H.261 standard is part of the H.320 group of standards for audio and visual communications. It forms the heart of many early-stage digital video applications in video conferencing and video communications systems, such as studio-based and desktop video conferencing, surveillance and monitoring, telemedicine, and computer-based training. In its later revision (the so-called version 2), H.261 allows a backward-compatible scheme for sending still picture graphics with 704 576 resolution.
As discussed in Chapter 3, MPEG-1 is a system-level standard which defines a group of audio and video (AV) coding and compression standards agreed upon by the MPEG committee. The MPEG-1 video coding standard [3] was...
