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Audio
While the use of audio in video surveillance systems is still not widespread, having
audio can enhance a system’s ability to detect and interpret events, as well as enable
audio communication over an IP network. The use of audio, however, can be restricted
in some countries, so it is a good idea to check with local authorities.
Topics covered in this chapter include application scenarios, audio equipment, audio
modes, audio detection alarm, audio compression and audio/video synchronization.
8.1
Audio applications
Having audio as an integrated part of a video surveillance system can be an invaluable addition
to a system’s ability to detect and interpret events and emergency situations. The ability of audio
to cover a 360-degree area enables a video surveillance system to extend its coverage beyond a
camera’s field of view. It can instruct a PTZ camera or a PTZ dome camera (or alert the operator
of one) to visually verify an audio alarm.
Audio can also be used to provide users with the ability to not only listen in on an area, but also
communicate orders or requests to visitors or intruders. For instance, if a person in a camera’s
field of view demonstrates suspicious behavior, such as loitering near a bank machine, or is seen
to be entering a restricted area, a remote security guard can send a verbal warning to the
person. In a situation where a person has been injured, being able to remotely communicate
with and notify the victim that help is on the way can also be beneficial. Access control—that is,
a remote ‘doorman’ at an entrance—is another area of application. Other applications include a
remote helpdesk situation (e.g., an unmanned parking garage), and video conferencing. An
audiovisual surveillance system increases the effectiveness of a security or remote monitoring
solution by enhancing a remote user’s ability to receive and communicate information.
AUDIO - CHAPTER 8
