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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.

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