User manual

Science Manual – Using Video Images for Fisheries Monitoring 17
Figure 3.6: A low-budget underwater bullet camera with 30 m of cable
3.5 Recording hardware
3.5.1 Mains-powered recording hardware
The best option for recording data is a computer-based recording system consisting
of a digital video recorder (DVR) card installed in a PC. The files can be recorded
onto an external or removable hard drive so that the data are portable and easy to
take back to the office for analysis or transfer to another machine if necessary.
Following analysis, the data can be copied in entirety onto an archive drive, short
sections of the movie file can be selected and stored or if there is no reason to store
the information, the data can be wiped off the hard drive.
A basic computer-based digital video system consists of a desktop PC with a DVR
card, such as the SuperDVR card produced by Voltek (Table 3.4), installed. The
DVR card may require a certain PC specification including a particular standard of
graphics card or the equivalent onboard graphics facilities, so be sure to check what
is required before you buy. These cards will record files in MPEG4 format, which is a
widely used digital video standard, so that the data are compatible with image
processing software. The DVR cards are supplied with easy-to-use software with
which to program the required settings. The user can change the frame rate at which
the file is recorded, set up a recording schedule, change the resolution and alter
other settings as required.
• MAINS-POWERED RECORDING
HARDWARE (PC + DVR card)
• 12-VOLT RECORDING HARDWARE
Low-power digital video recorders
Low-power computers