D-Link DCS-1100 - mydlink-enabled Wired Network Camera Uživatelský manuál stáhnout pdf (Strana 26)

101

Audio Compression – Audio Codec

 Advanced Audio Coding (AAC)

• Advanced Audio Coding (AAC) is a standardized encoding mechanism for digital

audio that uses lossy compression. AAC generally offers better sound quality

than MP3 at many bit rates. AAC encoding compresses more efficiently and thus

produces higher quality audio with smaller file sizes.

 Adaptive Multi-Rate (AMR)

• Adaptive Multi-Rate (AMR) is an audio data compression scheme optimized for

speech coding. AMR is now widely used in GSM and UMTS. It uses link

adaptation to select from one of eight different bit rates based on link conditions.

 Adaptive Differential Pulse-Code Modulation (ADPCM)

• ADPCM (adaptive differential pulse-code modulation) is a technique for

converting sound or analog information to digital information by taking frequent

samples of the sound and converting the value of the sampled sound modulation

in binary terms. ADPCM is used to send sound on fiber-optic long-distance lines

to store sound together with text, images, and codes to CD-ROM or other media.

IP Surveillance Essential

• Audio

102

Field of View

 There are three types of surveillance camera’s field of view:

• Normal View

Normal view offers the same field of view with human eye.

• Telephoto

Telephoto offers narrower field of view as compared to human eye, but better details of

image. This type of view is usually used for small or far surveillance object.

• Wide Angle

Wide angle offers wider field of view as compared to human eye, but lesser details of image.

This type is usually used for viewing larger areas of surveillance.

IP Surveillance Essential

• Lens Elements

Wide Angle Normal View Telephoto

103

Field of View

 There are three types of lens categorized based on how their field of view is

adjusted:

• Fixed lens

This type of lens provides fixed focal length and only supports one field of view,

either of telephoto, normal or wide angle, and is usually designed for optimal

resolution. A fixed IP camera usually has 4 mm focal length.

• Verifocal lens

This type of lens provides a variety of vocal length and supports different fields of

view. A verifocal IP camera offers a range of 3 mm to 8 mm focal length. One

limitation of such lens is that users need to manually refocus the lens every time

they change the field of view of the camera.

• Zoom lens

Similar to verifocal lens, Zoom lens gives users the flexibility of adjusting the

focal length and field of view. With zoom lens, users do not need to refocus the

lens when they adjust the focal length. A lens zoom capability is the ratio

between the lens’ shortest and longest focal length, for example in the case of an

8x-zoom, the shortest focal length will be 6 mm and the longest 48 mm.

IP Surveillance Essential

• Lens Elements

104

Matching Lens and Sensor

 When an IP camera offers an exchangeable lens feature, selecting a

suitable lens for the camera is one of the most important factor in order to

fully utilize the camera’s capability.

 If a smaller lens is used instead of the one that actually fits the image

sensor of the camera, the resulting image will have black corners (Left

Image below). If a larger lens is used instead of the one that actually fits the

image sensor of the camera, it will not fully utilize the lens’ field of view

(Right Image below), and will have a smaller field of field than the lens’

capability.

IP Surveillance Essential

• Lens Elements

1/2” Sensor

Black

Corner

2/3” Lens

1/2” Lens

1/3” Lens

1/2” Sensor1/2” Sensor

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 32 33

Komentáře k této Příručce

Žádné komentáře

D-Link DCS-1100 - mydlink-enabled Wired Network Camera Uživatelský manuál Strana 26

Komentáře k této Příručce

Související produkty a manuály pro Bezpečnostní kamery D-Link DCS-1100 - mydlink-enabled Wired Network Camera