Video and Media Servers: Technology and Applications, Second Edition

Compression Technology

Video compression technology has enabled more data to be stored in much less space. The 25 Mb/s motion-JPEG (M-JPEG) systems of several years ago have now migrated to MPEG-2 and DV. Bit rates are reduced to as low as 6-to-8 Mb/s (long GOP) with acceptable picture quality. Board sets for servers are gradually dropping the combination MJPEG/MPEG-2 codecs and producing only MPEG-2 or MPEG-2/DV sets.

Standardization on compressors and bit streams (e.g., MPEG transport streams) are enabling multiple video streams to be multiplexed into a single DS3-like format and transported over satellite to store-and-forward servers. High definition compressed video would not only be stored within the facility, but distributed direct to home either via satellite or 8VSB transmission.

Table 21-1: Hard Disk Drive interfaces and modes.

DRIVE INTERFACE DEVELOPMENT

INTERFACE

MODE

MAX DATA RATE

ATA-1

PIO-0

3.3 Mb/s

SCSI

SCSI

5 Mb/s

ATA-1

PIO-1

5.2 Mb/s

ATA-1

PIO-2

8.3 Mb/s

SCSI-2

Fast-Wide SCSI

10 Mb/s

ATA-2

PIO-3

11.1 Mb/s

ATA-3

PIO-4

16.7 Mb/s

SCSI-2

Fast-Wide SCSI

20 Mb/s

SCSI-3

UltraSCSI

20 Mb/s

ATA-4

Ultra

33 Mb/s

SCSI-3

Wide UltraSCSI

40 Mb/s

SCSI-3

Ultra2 SCSI

40 Mb/s

ATA-5

Ultra

66 Mb/s

SCSI-3

Wide Ultra2 SCSI

80 Mb/s

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