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DIGITALVIDEOCOMPRESSIONSTANDARDS 547intracoding of at least one macroblock in every 132. The
picture structure is based on the Group of Blocks, I and P
frames. According to section 4.2.2:Each picture is divided into groups of blocks
(GOBs). A group of blocks (GOB) comprises one
twelfth of the CIF or one third of the QCIF picture
areas (see Figure 6). A GOB relates to 176 pels
by 48 lines of Y and the spatially corresponding
88 pels by 24 lines of each of CBand CR.ITU-T H.261 supports motion compensation at only
full pixel resolution. ITU-T H.263 improves upon ITU-T
H.261 by using half-pixel precision for the motion com-
pensation and provides support for additional negotiablecoding options for improved compression performance. A
new ITU-T standard (tentatively named H.263+) is being
developed in cooperation with the MPEG committee.Proprietary Codecs
Cinepak (http://www.cinepak.com) and Indeo from Intel
(http://www.intel.com) are in common use in streaming
media applications. The Aware MotionWavelets codec
(http://www.aware.com) is a wavelet-based codec us-
ing only intra-frame compression. Qubit from Quvis
(http://www.quvis.com) is a three-dimensional wavelet
codec, which provides both spatial and temporal com-
pression. Note, in passing, that the wavelet-based codecs
soften the brightness edges in a manner that some
viewers and video editors find objectionable. These issuesTable 4Additional Well-Known Applications of Video Compression, Together with Requirements and Possible SolutionsApplication Requirements Possible Solutions
Video Conferencing (PSTN) 352 ×288 pixels at 29.97 fps, 24-bit color H.261, H.263, MPEG-4, Aware wavelet I frames
Compress about 73 Mbps to 56.6 kbps in
real time (about 1289:1)
Desktop Video Editing 1024 ×768 pixels at 29.97 fps, 24-bit color Cinepak, Indeo, MPEG-4, Aware wavelet I frames
Store 120-min movie on 18-MB disk
Compress about 468 to 18 MB (26:1)
Digital Cinema 1920 ×1080 pixels at 24 fps, 30-bit color Qualcomm ABS DCT (http://www.qualcomm.
com)
Transmit movie to theater over 45 Mbps line (Morley, 2000), Qubit (http://www.qubis.com)
Compress 1.5 Gbps to 45 Mbps (33:1)
Wireless Video One- and two-way scalable real-time
video from 160×120 pixels
monochrome to 640×480 with 24-bit
color over network without QoS at
9.6 kbps (iMode) and up to 2 Mbps
(Universal Mobile Telecommunication
System).MPEG-4 Visual with Dynamic Resolution
Conversion,
MPEG-4 Facial Animation wavelet video
(http://www.packetvideo.com,
http://www.envivio.com, http://www.
drfreedmaninc.com)Display video on small screens with low
resolution and with 33–200 MHz
requiring low power consumption for
extended battery life.
Home Shopping Customer sees and hears personal sales
assistant on television and then
customer speaks via telephone to
assistant in call center equipped with
camera, encoder telephone, call routing,
and graphics workstation.MPEG-2 (Simple Profile), MPEG-4 (http://www.
iseetv.net, http://www.avaya.com)Science When the Galileo spacecraft High Gain
Antenna failed to deploy close to Jupiter,
the mission required compression of
science and engineering data streams
from 13.4 kbps to 10 bps for
transmission via the S-band antenna.See Cheung and Tong (1993) noting particularly
the low complexity encoding on a small
onboard processor. The encoded imagery
could be unpacked with higher computing
power on Earth.
This situation is also relevant to two-way
wireless video.
Medicine Remote medicine and telesurgery—Full
motion virtual reality stereo video
compression over fiber optic, Internet 2,
or satellite links (subject to delays of up
to a few seconds)See Riva, Gamberini, and Davide (2001) and a
simulator at http://synaptic.mvc.acc.uk/home.
html.