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Copyright 2006 Psychonomic Society, Inc. 434
Journal
2006, ?? (?), ???-???
The purpose of this article is to give some insight into
digital video recording technology used in security sys-
tems to individuals who study behavior. The purpose is
to caution scientists who are contemplating switching to
digital surveillance systems. At first glance, these systems
would appear very practical to the behavioral scientist,
but the vast majority of systems available are designed
for security purposes, not for studying animal behavior,
and may not be compatible with Ethovision and The Ob-
server. The technology is very new, and although many
advantages are touted over traditional analog recording
(Table 1), scientists who have invested substantially in
these systems have reported difficulties, particularly re-
garding compatibility with behavioral analysis software
such as Ethovision or The Observer. The problem is that
security systems have multiple viewing functions required
for surveillance work but they generally contain propri-
etary compression and limited video export capabilities.
As a result, most systems export digital video to large files
that are in a format that is difficult for behavioral software
to use. In many instances, if a research group wishes to
utilize digital video, it may be better to continue to use
traditional methods of analog recording and to digitize the
video later, using a video capture device (either a PC card
or an external hardware device) that converts the analog
signal to a digital format. Other systems may be available
that could be adapted for research use, such as products
from the movie industry, but they are likely cost prohibi-
tive and are beyond the scope of this article.
What Is a Digital Video Recorder (DVR)?
Digital video recorders (DVRs) work in a fashion simi-
lar to that of a video cassette recorder (VCR), but they rely
on hard drives to store digital data, instead of video tapes
that record analog data. Digital video recorders can record
a video input stream from a variety of sources (Webcam,
capture card, video camera, or television broadcast) by re-
cording the video data and storing the data on a hard drive.
DVRs have all of the same functionality of VCRs (record-
ing, playback, fast forwarding, rewinding, and pausing),
plus the ability to instantly jump to any part of the re-
cording without having to rewind or fast forward the data
stream. The first DVRs that appeared on the market were
mechanical devices that resembled conventional VCRs,
with similar function keys, making them very familiar and
less intimidating, but the shortfall was that a price was
paid in terms of functionality. These devices are still avail-
able but are now also known as personal video recorders
(PVRs). The market demanded more, and soon personal
computer (PC) based DVR systems became available.
PC-based DVR systems are complete hardware/software
computer-based systems incorporating video capture,
video multiplexing, video/audio recording and playback,
The authors thank Derek Haley for help in reviewing the manuscript.
Correspondence concerning this article should be addressed to J. S.
Church, Livestock Welfare Unit, Alberta Agriculture, Food and Rural
Development, Room 306, 7000-113 Street, Edmonton, AB, T6H 5TC
Canada (e-mail: john.church@gov.ab.ca).
The use of digital video recorders (DVRs) for
capturing digital video files for use in both
The Observer and Ethovision
J. S. CHURCH and D. G. MARTZ
Alberta Agriculture, Food and Rural Development, Edmonton, Alberta, Canada
and
N. J. COOK
Alberta Agriculture, Food and Rural Development, Lacombe, Alberta, Canada
Before switching a laboratory from analog to digital, for the recording of video files for use in Noldus
software such as Ethovision and The Observer, researchers need to proceed with caution. There are
obvious advantages in moving to digital recording for behavioral work, including increased storage
capacity; no requirement to purchase video tapes; immediate search by date, time, or event; digital
images are of higher quality; ability to view study sites remotely by Internet connection; and “smart”
features, such as motion detection. But before you throw away your time-lapse video recorders, time
code generators, and video multiplexors, there are some important cautions to take account of. Some
research groups have bought digital surveillance systems on the assumption that they work with Etho-
vision and The Observer, only to be disappointed. The vast majority of systems depend on proprietary
compression software that must then be converted to work properly in Ethovision or The Observer.
Behavior Research Methods
2006, 38 (3), 434-438
DVR USE FOR THE OBSERVER AND ETHOVISION 435
video display, and remote video access via modem, Inter-
net, or local area network. More recently, advances have
been made with high-end digital non–PC-based DVRs that
can duplicate the functions of a PC-based DVR. These em-
bedded DVRs do not use a Windows operating system and
contain no software at all on the hard disk(s). All applica-
tions are contained, or embedded, in firmware (software
encoded on chips). Mobile DVRs are embedded systems
that were originally developed for use in vehicles. They
incorporate antishock and antivibration mountings and
generally have 12-V DC power inputs. At the heart of any
DVR system is a video capture card or a similar device.
They are called capture cards because they “capture” and
record the video (encoding), but they are also responsible
for playback and display of the video on screen (decod-
ing). The other component most often includes some kind
of CCTV (closed circuit television) camera. Digital video
recorders are sophisticated integrated systems composed
of a combination of hardware components, software pro-
grams, and subassemblies. These systems are most com-
monly used for security monitoring purposes via video
surveillance and should not be confused with set-top con-
sumer cable boxes such as TiVo. Although these are also
referred to as DVRs, the purpose and function of the two
systems are different.
Problems With Implementing Security-Based
Systems for Behavioral Research
In purchasing a surveillance system, the first priority
should be to assess and understand your needs. It is im-
perative that the system accomplish exactly what you want
it to do; otherwise, the capital expenditure required to pur-
chase the system will be wasted. The problem is that most
of the companies and individuals selling these systems
are unfamiliar with the unique application of the DVR for
behavioral observation and simply assume that the system
will work. From a hardware perspective, the systems seem
simple enough; most comprise two main components:
cameras and a DVR. However, within each of these two
components, there are a number of choices to consider,
with prices varying significantly. In April 2005, the In-
ternational Security Conference and Exhibition West was
held in Las Vegas. The conference was attended by 21,000
industry participants with 825 exhibitors. Of the exhibi-
tors, one third (246) were promoting some combination of
camera/DVR system for security monitoring. Generally,
all of them are custom-built systems, and consequently,
there is a lack of standardization between products. This
especially raises problems for the scientist who is trying
to select the appropriate digital recording system to meet
specific behavioral observation needs. Some problems
encountered with implementing security-based systems
for behavioral research are the following: Specific sys-
tems often work with only certain cameras; the quality
of the recorded video is less than optimal; recorded and
display speeds are not what has been stated; they are un-
able to play back video on computers or machines other
than the one on which it has been recorded; the numbers
of days of storage is less than what has been specified; no
local support is available for the product; the file format,
when decoded, is not compatible with Ethovision and The
Observer; and frames are intermittently dropped, due to
processor use, but the audio is recorded continuously, re-
sulting in video and audio that is out of sync and virtually
unusable.
Understanding Compression Formats
Working with digital video requires a large amount of
storage capacity, and digital video generally needs to be
compressed before it can be stored. All companies provide
some form of their own proprietary compression. Com-
pression technology is based on mathematical algorithms.
Compression is performed when an input video stream is
analyzed and information that is indiscernible to the viewer
is discarded. It is actually a case of compression and decom-
pression: Information is compressed to travel down the net-
work and then decompressed for transmittal when it comes
out the other side—hence, the name codec. A video codec
is software that can compress a video source (encoding), as
well as play compressed video (decoding). Standards are
set by the International Organization for Standardization—
a nongovernmental organization that works to promote the
development of standardization in order to facilitate the in-
ternational exchange of goods and services and to encour-
Table 1
Advantages of DVR Versus Analog Recording
Characteristic Digital Analog
Search ability Instant by date, time, or Manual search
event
Storage capacity Months of footage, high Requirement to buy
capacity, no degradation of videotapes, quality degrades
quality over time over time
Duplication No signal or quality loss on Video signal degradation on
recording, copying video is rerecording or duplication,
virtually instant copying video is in real time
Image quality High quality Poor image quality
Remote monitoring View multiple locations Limited monitoring capability
over Internet
Intelligent features Motion detection, remote No intelligence
notification
436 CHURCH, MARTZ, AND COOK
age worldwide intellectual, scientific, technological, and
economic activity—and the International Electrotechnical
Commission, the international standards and assessment
body for the field of electrotechnology. These two indus-
try bodies recognize a number of standard compression
formats, including MPEG-1, MPEG-2, MPEG-4, Morgan
JPEG (MJPEG), Wavelet JPEG, H.264, and so forth. Man-
ufacturers purchase a license to utilize one of these com-
pression formats, but many attempt to “tweak” the format
themselves, making the format unstable for use with either
Ethovision or The Observer. AVI is especially problematic,
but nevertheless, it is a format that many digital surveillance
companies use. It is important to note that Ethovision does
not support all formats of AVI (such as DivX) or MPEG-4.
It is important to recognize that the market is changing
fast and that new standards are rapidly emerging. Much of
the information with regard to compression formats will
likely be obsolete in 5 years. MPEG-4 has emerged as one
of the new standards for both multimedia and Web com-
pression. MPEG-4 is based on object-based compression;
individual objects within a scene are tracked separately and
compressed together to create an MPEG-4 file. This results
in efficient compression that is very scalable, from low bit
rates to very high. It also allows developers to control ob-
jects independently in a scene and, therefore, introduces
interactivity. As a result, it has become a popular format in
the digital surveillance industry and will likely become a
new standard in the future. MPEG-4 is now available and
compatible with The Observer XT that has recently been
released from Noldus. However, it is important to reiterate
that it is still not compatible with Ethovision. In our experi-
ence, for the majority of researchers, it is best to stick with
either MPEG-1 or MPEG-2 in order to maintain compat-
ibility with behavioral software packages.
MPEG-1
. MPEG is a file format for compressing full-
motion digital video that was produced by the Moving
Picture Expert Group of the International Standards Orga-
nization. It was originally designed for up to 1.5 Mbit/sec.
For the last couple of years, MPEG-1 has been the stan-
dard for the compression of moving pictures and audio.
This format was primarily used for CD-ROM video ap-
plications, and it is still a popular standard for video for
use on the Internet, transmitted as *.mpg files. MPEG-1
is the standard of compression for VideoCD, the most
popular video distribution format throughout most of
Asia. Of interest, Level 3 of MPEG-1 is also the standard
of digital compression for audio, better known as MP3.
Although MPEG-1 produces better results than do Quick-
Time (.mov) and AVI, the MPEG-1 standard provides a
video quality that is slightly below that of traditional VCR
analog recording. The advantage of MPEG-1 is that the
files are relatively small (about 10 MB/min) and, there-
fore, take up less storage space. A further advantage is that
MPEG-1 software decompression comes standard on the
Windows operating systems, so it will work on a variety
of computers. If continuous observation is an important
consideration, or if observation is going to take place over
a long period of time, and quality may not be imperative,
this is a very useful format to use.
MPEG-2
. The MPEG-2 format offers higher video
quality than does MPEG-1, but the downside is that the
file size increases dramatically (about four times the size,
or approximately 40 MB/min). MPEG-2 is the standard
on which most digital television set-top boxes and com-
mercial DVD compression are based. Although it is based
on MPEG-1, it was designed for the compression and
transmission of digital broadcast television. The advan-
tage of MPEG-2 is the improved quality, sufficient for all
the major television standards, including NTSC. The most
significant improvement over MPEG-1 is its ability to
compress interlaced video. MPEG-2 scales well to HDTV
resolution and bit rates, which essentially eliminates the
need for MPEG-3. In terms of quality for behavioral ob-
servations, MPEG-2 is adequate for the vast majority of
behavioral researchers.
Considerations of storage
. The primary advantage
of digital video is that it is easier to manipulate with
Noldus software than are analog sources; also, hardware
prices have decreased rapidly in recent years. However,
digital video still requires considerable storage capacity
and needs to be compressed before it can be stored on
a disk medium. Most DVR systems have a lot of flex-
ibility in terms of file storage. Often, files can be stored
on large hard drives or even stored on the departmental
server over a network. Many systems included CD/DVD
burner software, allowing the end-user to burn the files to
a CD or DVD for archival storage, and some miniaturized
systems are designed to work with memory sticks. Due
to the large size of the digital video files, most users will
want to store to a DVD format. However, there are multi-
ple DVD formats. DVD stands for Digital Versatile/Video
Disc, DVDR stands for DVD Recordable, and DVDRW
for DVD ReWritable. This medium looks very similar to
regular audio/music compact discs or DVD-Video discs
that are sold by the recording and movie industries. There
are three competing DVD recording standards or formats;
DVD-R/DVD-RW (supported by the DVDForum), and
DVD+R/DVD+RW (supported by the DVD Alliance),
which have pretty similar features and are compatible with
many standalone DVD players and recorders, whereas
DVD-RAM has less player and recorder compatibility
but better recording features. It is important to determine
which format is compatible with the individual DVR under
consideration. DVD-RAM has the best recording features,
but it is not compatible with most DVD-ROM drives and
DVD-Video players. This format should be considered
more as a removable hard disk (this format is supported
by the DVDForum).
As was mentioned previously, digital video needs to
be compressed before it is stored on a disk medium. With
many DVR systems on the market, you can set the sound
and image quality of the resulting media file. However,
the higher the quality, the larger the file. Thus, the high-
est quality of images and sound require a large amount of
space on the disk. In practical terms, most users select their
quality with the capacity of their long-term storage media
in mind. For example, with an MPEG-1 of 10 MB/min,
you can fit about 1 h of video onto one CD (700 MB).
DVR USE FOR THE OBSERVER AND ETHOVISION 437
Both DVD-R and DVD-RW support single-sided 4.37-GB
DVDs (called DVD-5) and double-sided 8.75-GB DVDs
(called DVD-10). Some disks are dual layered. A dual-
layer writable DVD+R or DVD-R can hold 7.95 GB
(called DVD-9), and dual-layered double-sided disks can
hold 15.9 GB (called DVD-18).
Considerations about frame rate
. An important con-
sideration when analyzing specifications of a DVR system
is to clarify frame, or images, per second. Many labs have
reported that the frame rate promised has not been the same
as the frame rate realized under laboratory conditions. The
frame rate issue is very tricky. The fact is the speeds that
manufacturers quote are usually the “maximum” obtain-
able, meaning those obtainable under ideal conditions,
and do not take into account other functions that the PC,
software, or video card might be processing simultane-
ously. There are an infinite number of ways of presenting
these numbers, and the numbers can often be misleading.
A standard in the marketplace is 30 frames/sec, which is
considered to be real-time/real-motion video, but that is
for a single video stream. For example, if four cameras
are recording simultaneously, all in real-time/real-motion
video, 120 frames/sec with full unshared resources is re-
quired. It is very important that frame rate be clarified;
for example, the manufacturer may be discussing the fol-
lowing: the total number of frames/images/sec for the en-
tire card spread across all cameras (cumulative total); the
total number of frames for each individual channel; the
maximum frame capacity of the hardware, not taking into
account software switching, simultaneous functions, and
so forth (rated hardware capacity); the display speed; the
recording speed; or a combination of all of the above.
Advantages of DVR
One of the immediate advantages of digital versus an-
alog recording for behavioral observation is that digital
video no longer requires special hardware for reading time
codes, controlling the video, or displaying an image or
multiple images on the monitor. Most DVR systems have
software solutions that negate the need for many tradi-
tional hardware requirements in an analog-based system,
such as time code generators, video signal splitting de-
vices, or even time lapse video recorders. In most cases,
the DVR can provide all of those things. The advantages
and disadvantages of DVR and analog video are outlined
in Table 1.
New features of DVR
. The reality is that DVRs are
part of a very young technology; new features are continu-
ally emerging, and the bar is being pushed higher every
day. With constant demand for new features, a powerful
foundation is required. But new features mean new un-
known variables and accompanying problems.
It is important to remember that the software that is pro-
vided with the DVR system is the foundation of the sys-
tem and at least as important as the hardware. At the heart
of any good DVR software program is a solid database
structure. Hardware components aside, the architecture of
the software’s database is the single most important part of
the DVR. How the database stores the video files and what
happens when multiple users simultaneously access the
database are important issues that must be resolved. What
happens when you have to search through thousands of
files or conduct queries? How long does it take to convert
or export the files from compressed files to files that the
user can actually use? What file format will ultimately be
used with the behavioral software package? These are all
important questions that the end-user must be aware of.
Motion detection is an exciting new feature of many
DVR systems. Motion detection essentially allows for a
motion-detection–triggered record function or alarm. Mo-
tion detection is a very useful alternative to simple con-
tinuous recording. Often, continuous recording is used by
behavioral scientists because they do not want to miss a
behavioral activity or event that is difficult to detect with
scan sampling. By recording only when activity is occur-
ring, one can store significantly more video on the hard
disk, but more important, the researcher does not waste
time on playback watching when no activity is occurring.
Often, the system can be preset to capture a brief time seg-
ment prior to the motion’s occurring, which could be very
useful data. Along with motion detection, many systems
allow the user to specify an area within the field of view
of a camera and perform a search for any motion that oc-
curs within that zone, a useful feature that could be used
to refine behavioral tracking with Ethovision.
Another useful advantage of DVR systems, in compari-
son with other alternatives, is the ability to monitor the
system remotely over the Internet. In order to connect the
DVR to the Internet from a remote location, generally all
that is required is an IP address of the location where the
DVR is situated. In addition, many systems not only allow
one to remotely view cameras simultaneously, but also
allow one to manage the main functions of the DVR as
well. And finally, cameras can be locally or remotely con-
trolled for panning, tilting, and zooming. It is important
to caution the user, however, about the pitfalls of keeping
a recording computer connected to the Internet. Often,
automatic software updates, antivirus software, and other
externally directed processes can reduce available pro-
cessing from the CPU and may interfere with the file’s
being recorded.
The inclusion of diagnostic software, which constantly
monitors different functions of the hardware and software
of both the DVR and the server or other storage medium,
is also very useful. If the diagnostic software detects any
deviations from the established baseline criteria, the sys-
tem can notify the system administrator that it has de-
tected a problem. The inclusion of remote diagnostic soft-
ware, which allows the research scientist or a technician
to monitor system performance and diagnose and repair
potential problems remotely, is also very useful. This fea-
ture could save on unnecessary service calls to the DVR’s
physical location, which may be thousands of miles away
from support personnel.
Often, the ability to time/date stamp the data file is a
feature built into many systems. In the future, it is very
likely that additional data will be readily superimposed
on the video files generated from DVR systems. Already
438 CHURCH, MARTZ, AND COOK
POS (point of sale) information is being included as em-
bedded text on the video files in some DVR systems used
for security surveillance in the restaurant industry. The
ability to include additional data, such as physiological
or environmental measures, will likely become standard
features of many DVR systems in the future.
Important questions to ask about DVR
. The biggest
obstacle within the DVR industry that researchers need to
be aware of is that a number of entities that were already
in the security business in the last generation of CCTV
technology have attempted to cross over into a world that
is far removed from their core competence. DVR systems
are primarily an information technology product. Noth-
ing within the last generation of CCTV resembles this,
nor does it lend itself to a knowledge base that is readily
transferable. The last generation of surveillance equip-
ment depended on mechanical analog-based products,
which are, in essence, fixed machines. As this article has
outlined, DVRs are sophisticated network appliances that
are primarily software based. Many companies have en-
tered this business with the best of intentions but have
become quickly overwhelmed. With each new company
that enters into the marketplace, another one goes out of
business. Unfortunately, the number of assemblers and
would-be manufacturers are in the thousands, and the
number continues to grow. There are, however, a number
of key questions that a researcher should ask the supplier
when considering a switch from an analog to a DVR-based
system:
What experience do they have with the product?
How long have they been in business?
If you have a problem who do you call?
How long does it take to get service?
Where are their service centers located?
Are the end files that are generated compatible with
Noldus behavioral software?
In this article, we have attempted to cover the basics
on the use of DVRs designed for security surveillance in
behavioral research, how they work, and their components
and software, as well as related concerns. On the basis
of the facts presented in this article, we are hopeful that
behavioral researchers will formulate the right questions
before acquiring a new DVR-based system.
(Manuscript received September 30, 2005;
revision accepted for publication January 21, 2006.)
