HD Player
Index
113
Rev. 6.4
block. In level 4 the parity disk receives excessive load for writes and no load for
reads. In Level 5 the load is balanced across the disks.
Resolution
•
Detail. In digital video and audio, the number of bits (4, 8, 10, 12, etc.)
determines the resolution of the digital signal. Four bits yields a
resolution of one in 16. Eight bits yields a resolution of one in 256. Ten
bits yields a resolution of one in 1,024. Eight bits is the minimum
acceptable for broadcast television.
•
A measure of the finest detail that can be seen, or resolved, in a
reproduced image.
While influenced by the number of pixels in an image (for high definition
approximately 2,000 x 1,000, broadcast NTSC TV 720 x 487, broadcast PAL
TV 720 x 576), note that the pixel numbers do not define ultimate resolution but
merely the resolution of that part of the equipment. The quality of lenses, display
tubes, film process and film scanners, etc., used to produce the image on the
screen must all be taken into account. This is why a live broadcast of the Super
Bowl looks better than a broadcast recorded and played off of VHS, while all are
NTSC or PAL.
RS-232
A standard, single-ended (unbalanced) interconnection scheme for serial data
communications
RS-422
A medium range (typically up to 300 m/1000 ft or more) balanced serial data
transmission standard. Data is sent using an ECL signal on two twisted pairs for
bi-directional operation. Full specification includes 9-way D-type connectors
and optional additional signal lines.
RS-422 is widely used for control links around production and post areas for a
range of equipment.
Sampling
Process by which an analog signal is measured, often millions of times per
second for video, in order to convert the analog signal to digital. The official
sampling standard for standard definition television is ITU-R 601.
For TV pictures eight or 10 bits are normally used; for sound, 16 or 20-bits are
common, and 24-bits are being introduced. The ITU-R 601 standard defines the
sampling of video components based on 13.5 MHz, and AES/EBU defines
sampling of 44.1 and 48 kHz for audio.
Sampling
frequency
The number of discrete sample measurements made in a given period of time.
Often expressed in megahertz for video.
SCSI
Small computer systems interface. A very widely used high data rate, general
purpose, parallel interface. A maximum of eight devices can be connected to one
bus, for example a controller, and up to seven disks or devices of different types
- Winchester disks, optical disks, tape drives, etc.- and may be shared between
several computers.
SCSI specifies a cabling standard (50-way), a protocol for sending and receiving
commands and their format. It is intended as a device-independent interface so
the host computer needs no details about the peripherals it controls. But with two
versions (single ended and balanced), two types of connectors and numerous
variations in the level of implementation of the interface, SCSI devices cannot
"plug and play" on a computer with which they have not been tested. Also, with
total bus cabling for the popular single ended configuration limited to 18 feet (6
meters), all devices must be close.
