fuhrman diversified, integrated systems guaranteed to do what you need a video system to do. fieldcam
Introduction Fieldcam custom closed circuit video systems
questionnaires
Custom System Types
System Components
White Papers
video tutorial trail

  MULTI-CAMERA SYSTEMS

Multi-camera systems using one recorder for two or more remote cameras require careful analysis of the following parameters:

A.     Are the subjects to be viewed by the cameras close enough together to allow reasonable cable lengths from the cameras to the recorder?  Will the same be true of future projects for the system or will you have to buy additional recorders for future projects?

B.      Are the levels of activity at each site sufficiently similar that the same temporal interval can be used for all cameras?

C.        Do you plan on using the recording system for analysis playback?  If recording and analysis are to be done simultaneously at different location,  additional hardware is required for the analysis location.  Some exceptions to this are possible if a networkable digital recorder has internet or data network (T1, LAN, etc.) access, since certain digital recorders can be remotely downloaded to offsite computers while the recorder is actively recording new images.

Multi-camera recording technology and terminology

Multiplexing

Sequential digital switching, compression and recording of the images from two or more cameras onto the recording media that is synchronized with the recording interval chosen at up to 60 images per second per channel.  As the images are passing through the multiplexing system, a flag is placed on each image going to the recorder to indicate the camera of origin.  During recording or playback,  the images from each camera can be placed in a specific location on the monitor or the images can be displayed sequentially or any individual camera can be played back at full screen size at full resolution unlike quad processor units which have highly degraded images when a single camera is displayed full screen size. Certain digital multiplexer recording systems allow remote monitoring by internet / local network (dialup , DSL, LAN, WAN, T1 etc.) of live video or previously recorded video while the multiplexer continues to record.

It is very important to remember that the recording interval is not the Temporal Interval (TI).  For example if the recording interval is 1 second and 4 cameras are being recorded, the TI is 4 seconds.  If subjects are moving quickly,  data could easily be lost in that interval.  Because of this potential data loss factor, we rarely build systems using multiplexers with more than 4 channels even though units from the security industry can have as many as 32 channels

PIP

Picture in picture is sometimes useful when only two cameras are required and a second monitor is not wanted since both images can be displayed on the same monitor.  It is also the technique of choice when the images from each camera must be recorded simultaneously.  Simultaneous imaging is usually required for fast moving subjects that require orthogonal or stereo imaging. 

There are two technologies available to create PIP.  A digital technique which digitizes the images from both cameras  and allows the insertion of the full image of either camera into a small image (usually) at the bottom of the monitor screen.  A switch allows image choice.  This technology can be used with virtually any two cameras but after recording the images cannot be interchanged nor can one image alone be displayed.



The alternate technology uses only certain types of cameras that can be synchronized or genlocked.  A master camera is chosen to synchronize a slave camera.  When this is done, either camera can be adjusted to fill all or part of the monitor image.  However they are not the full image of each camera but only a that portion which you display on the screen.  Again after recording the images cannot be interchanged nor can one image alone be displayed.



Quad processor image systems

A technology that allows the images from up to four camera to be simultaneously recorded as a single image on the media. The problem is that 3/4s of the pixels from each camera image is not recorded and that the image quality if you try to enlarge the 1/4 image to full size is very poor. After recording one image can be displayed but the quality is very poor.  This technology is not recommended.



 

Home | Introduction | Questionnaires | Custom System Types | System Components
White Papers | Video Tutorial Trail | Contact Us | Site Map

©Copyright 2007, Fuhrman Diversified, Inc.
FIELDCAM, FIELDCAM WCMS, FIELDCAM BASIC, FIELDCAM TLV, MDP AND BURROW PROBE
ARE TRADEMARKS OF FUHRMAN DIVERSIFIED INC.