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H.263:
A standard for variable low bit rate coding of video. H.263 is better than
MPEG-1/MPEG-2 for low resolutions and low bit rates. H.263 is less
flexible than MPEG, but therefore requires much less overhead. HD-0: A
set of formats based partially on the ATSC Table 3, suggested by The DTV
Team as the initial stage of the digital television rollout. Pixel
values represent full aperture for ITU-R 601. The DTV Team's HD0
Compression Format Constraints.
HD-1:
A set of formats partially based on the ATSC Table 3, suggested by The
DTV Team as the second stage of the digital television rollout, expected
to be formalized in the year 2000. Pixel values represent full aperture
for ITU-R 601. (Items in bold have been added to HD-0.) The DTV Team's
HD1 Compression Format Constraints.
HD-2:
A set of formats partially based on the ATSC Table 3, suggested by The
DTV Team as the third stage of the digital television rollout contingent
on some extreme advances in video compression over the next five years.
Pixel values represent full aperture for ITU-R 601. (Items in bold have
been added to HD-1.) The DTV Team's HD2 Compression Format Constraints
HD
D5: A compressed recording system developed by Panasonic which uses
compression at about 4:1 to record HD material on standard D5 cassettes.
HD D5 supports the 1080 and the 1035 interlaced line standards at both
60 Hz and 59.94 Hz field rates, all 720 progressive line standards and
the 1080 progressive line standard at 24, 25 and 30 frame rates. Four
uncompressed audio channels sampled at 40 kHz, 20 bits per sample, are
also supported.
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HDCAM:
Sometimes called HD Betacam--is a means of recording compressed
high-definition video on a tape format (1/2-inch) which uses the1125/60
markets and supports both 1080 and 1035 active line standards.
Quantization from 10 bits to 8 bits and DCT intra-frame compression are
used to reduce the data rate. Four uncompressed audio channels sampled
at 48 kHz, 20 bits per sample, are also supported.
HDTV:
High definition television. The 1,125-, 1,080- and 1,035-line interlace
and 720 and 1,080-line progressive formats in a 16:9 aspect ratio.
Officially a format is high definition if it has at least twice the
horizontal and vertical resolution of the standard signal being used.
There is a debate as to whether 480-line progressive is also high
definition. It is the opinion of the editors that 480-line progressive
is not an HDTV format, but does provide better resolution than 480-line
interlace, making it an enhanced definition format.
HFC:
Hybrid fiber coax. A type of network that contains both fiber-optic cables
and copper coaxial cables. The fiber-optic cables carry TV signals from
the head-end office to the neighborhood; the signals are then converted
to electrical signals and then go to coaxial cables.
HIPPI:
High performance parallel interface. A parallel data channel used in
mainframe computers that supports data transfer rates of 100 Mbps.
Huffman coding: This compresses data by assigning short codes to
frequently-occurring sequences and longer ones to those less frequent.
Assignments are held in a Huffman Table. The more likely a sequence is
to occur the shorter will be the code that replaces it. It is widely
used in video compression systems where it often contributes a 2:1
reduction in data.
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