Axis 2400+ Manual do Utilizador descarregar pdf (Página 31)

The size of digital images is measured in kilo Bytes.

Digital images can be stored on a computer hard disk,

the capacity for which is measured in Giga Bytes.

Several million digital images can be stored onto a

single hard disk. When the hard disk is full, the old

images can be erased automatically to make space for

new ones. Network video products effectively eliminate

the job of switching tapes.

1 kB (kilo Bytes) ~ 1,000 Bytes

1 MB (Mega Byte) ~ 1,000,000 Bytes

1 GB (Giga Byte) ~ 1,000,000,000 Bytes

1 TB (Tera Byte) ~ 1,000,000,000,000 Bytes

Example

One image per second, 24 hours per day for almost two

months can be stored on one 120 GB hard disk. Each

image will be of much higher quality than an image

from a VHS tape.

A typical size of a high-quality image is 25 KB

A typical size of a hard disk is 120 GB

120,000,000,000 Bytes / 25,000 Bytes = 4,800,000

4,800,000 / 60 sec. / 60 min. / 24 h = 55 days

Storage and transmission

Images can be stored and transmitted by analog or digital means. Traditional

analog video cameras transmit images over a coax cable and store them on

magnetic tape. Although this works well in many cases, the image quality

is lower when the video signal is transmitted over long cable distances. The

resolution of a magnetic tape can also be quite low. By comparison, digital

images never lose quality during transmission or storage.

One 120 GB hard disk can store 4,8 million still images. This is equivalent to 9 VHS tapes (E180).

A NALOG VS. DIGITAL

VHS TAPE E120

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 51 52

Sem comentários

Axis 2400+ Manual do Utilizador Página 31