User manual

18 Science Manual – Using Video Images for Fisheries Monitoring
Standardised format: Is it
compatible?
Digital recorders are reasonably cheap and some
may be attractive low-power options. But beware of
compatibility problems. Many will store data in a
proprietary format that has to be converted to a
standard format to be shared or analysed with
software. For this reason, we have favoured
standard PCs with digital video cards for collecting
video files and sourced a suitable low-power PC.
A system such as this can be
used to record video files which
can then be bought back to the
office and either watched
(applicable for video validation
of other counters) or played
back through image capture
and review software such as
Fishtick (Section 3.7). A less
labour-intensive method of
collecting data involves
installing image capture
software on site and bringing data back for review only.
The image processing and analysis packages described in Section 3.7 determine the
specification of the computer.
3.5.2 Twelve-volt recording options
If it is not possible to access mains power at a site or for simple exploratory work,
there are recording systems which will operate on a 12-volt power supply. What you
choose will depend on your budget, the amount of data you wish to collect and how
you plan to use it.
Low-power digital video recorders
Buyer beware: Many commercial digital video recorders store data in a proprietary
data format. Image analysis or motion detection tools designed for data in a standard
MPEG format will not work with proprietary data. Check that the product you are
buying can save data to an MPEG format and not just provide a process to convert it
later.
Low-power 12-volt digital video recorders such as Timespace Technology X200 DVR
have been used by Environment Agency teams in Wales and in the South West.
When choosing a DVR, things to look out for include whether the camera can take
multiple video inputs, and
what media the data are recorded onto (such as a removable hard disk cartridge).
Most DVRs will have a range of recording options including timer, schedule and
alarm recording. It is useful if the DVR is supplied with a reviewer as this allows the
user to program settings, watch the live feed in order to set the cameras up correctly
and review recordings. Alternatively, a battery-powered video monitor, such as the
CCTV test monitor supplied by System Q (Table 3.4), can be used. After the
required data have been collected, the removable storage media can be taken away
for review and the data downloaded to PC.
The cost and functionality of digital video recorders can vary widely. For example, at
£2,400 the Timespace X200 is the most expensive 12-volt recording option tested for
this project (Table 3.2), being more comprehensive than the other two systems
discussed here. It has a huge range of menu options, many of which are not
applicable for the type of fish counting set-up required, which makes it more complex
than necessary to configure.