The Good, the Bad and the Blurry

A Comprehensive Look at Analog and Digital

An armed robbery turns deadly when the perpetrator guns down a clerk. There were no living witnesses to the crime. Investigators search the scene for clues. Two different video surveillance systems are found covering the area of the crime: one inside the store and the other at the adjacent gas station. One video surveillance system is connected to an analog timelapse recorder. The other system is connected to a digital video recorder (DVR). One system provides evidence that is easy to recover and usable video images of the suspect. The other system...not so much. Which system, analog or digital, is causing the problems and why?

“The hard drive containing the video evidence is sometimes worthless without the DVR it came from. It would be like seeing a beautiful fingerprint at a crime scene but being unable to photograph or lift it for analysis."

Some people may be surprised to hear that the video surveillance system connected to the DVR is causing problems for law enforcement. Most information disseminated about digital technologies is that they are far superior to the older analog technologies. It’s digital, so it must be better. While that may be true for some technology, it is not necessarily true for the video surveillance marketplace. Propaganda from security manufacturers and installers tells a wild tale of image quality vastly superior to analog videotapes and features that make digital easier to use. From the perspective of law enforcement, nothing could be further from the truth.

One of the most important features for any video surveillance system is the ability to archive critical information onto removable media. The system needs a feature for the recovery of video evidence that can be submitted for analysis. On an analog system, the evidence is recorded to a videotape. This videotape is ejected from the timelapse VCR and submitted as evidence for analysis. Analog video surveillance systems incorporated this feature by default. Videotapes contained the evidence and their portability from system to evidence was simple.

On a digital system, the evidence is recorded to a hard drive. In comparison to an analog system the hard drive would be “ejected” from the system and submitted as evidence for analysis. Unfortunately, it’s not that easy. Some DVRs do utilize a removable hard drive enclosure in their design. This design makes it easy to “eject” the hard drive and submit it as evidence. One drawback of this design is the cost to replace the drive. If a videotape is seized as evidence, the cost to replace that videotape is around two dollars. The cost to replace the hard drive and its removable hard drive enclosure may cost $300
or more. The other drawback occurs when the hard drive is submitted as evidence. The data on the hard drive may be useless to the forensic video analyst. The hard drive containing the video evidence is sometimes worthless without the DVR it came from. It would be like seeing a beautiful fingerprint at a crime scene but being unable to photograph or lift it for analysis. Submitting a hard drive from a digital video surveillance system does not ensure that the evidence is in a format that can be used for analysis.


Not all of the DVRs use removable hard drive enclosures. To access the hard drive the system could be taken apart, screw by screw. Is it worth the effort to go this far in all cases? Consider also the size of the hard drive. Is it worth all the trouble to seize 500 Gigabytes of data that contain 30 days of information for a 15 minute crime? Is it worth all the trouble to seize 5 Terabytes of data that hold 365 days of information for a 15 minute crime? In some cases, the answer may be yes. In the vast majority of cases, the answer most definitely will be no. Removing the hard drive is not always the answer for recovery from digital video surveillance systems.

Knowing that replacing hard drives is expensive and those critical incidents needing to be archived may be short in duration, manufacturers of DVRs have incorporated alternative archival procedures. CD/DVD writers, USB connections, network connections, and flash media drives have all been included among others as methods for archiving video data from a DVR. Some of these methods may seem easy – a digital equivalent to “eject the videotape” from analog timelapse recorders. These alternative methods for recovering video evidence must be reviewed in terms of ease of use and image quality.

The ease of use issue also applies to the resulting video data that is archived from the DVR to the removable media. With each success of recovering the video evidence from a digital video surveillance system, comes the inevitable question: what does the video data need in order to play back? Just like the removable hard drive may need the DVR to play the video, the video data on a CD, DVD or any other media may need proprietary software in order to play back. Some DVRs may include this as part of the archiving package with the video data but many others do not. So the evidence we gather and bring back for analysis is useless without that player. Proprietary players are another hazard of the video recovery process.

The second factor with archival features is image quality. The archival feature may include the ability to provide video evidence as a standard file format. This may seem like an excellent choice. Video that is stored in a standard file format may be viewed from readily available players like Windows Media Player. The problem with these formats is that they often recompress the original data. A good comparison to this process would be to photocopy a document. The information is there but the quality is not the same. Having an archival feature that degrades the image quality is not an acceptable solution.

Video surveillance systems are quickly switching from analog videotape to digital video data. The illustration offered by the manufacture and designers of DVRs as being superior in quality and ease of use has yet to be realized. So what should law enforcement do? The answer is education, equipment, and standard operating procedures. With the strategy outlined below the recovery of video evidence from digital surveillance systems will be feasible. The resulting evidence will provide law enforcement with video information that can be used for investigative purposes and evidence in a court of law.

With analog video surveillance systems education was designed mostly for the forensic video analyst. This person was responsible for the enhancement of the video evidence for investigative purposes. The detective or crime scene analyst responsible for recovering the video evidence may or may not have received any training on this type of technology. From a recovery perspective analog video surveillance systems seemed very straightforward: recover the videotape and bring it to the forensic video analyst. It was the analyst who needed to know how to play it back, what tools were available for enhancing the evidence, and how to produce the derivative evidence that aided the investigation. Education was critical for providing these skills.

Now with digital video surveillance systems education must be provided to the person responsible for recovering the evidence and the forensic video analyst. The detective or crime scene analyst must have some understanding of computer technology and the design of DVRs. They must also be aware of the typical methods available for recovering video evidence as well as the pitfalls of each. With this education they will be able to look for the best evidence from a DVR and be able to make the right decisions in deciding what to keep as evidence. Education on surveillance systems should be available for each person who handles digital video evidence.

With analog videotapes, the most expensive purchase was for the forensic video analysis system to capture and enhance the video evidence. With today’s digital surveillance systems, money will also need to be invested in equipment for the recovery of video evidence.

Equipment is also a necessity for law enforcement in the pursuit of digital video evidence. With analog videotapes, the most expensive purchase was for the forensic
video analysis system to capture and enhance the video evidence. With today’s digital surveillance systems, money will also need to be invested in equipment for the recovery of video evidence. This recovery kit needs to be designed to handle a variety of archival methods. Not only should removable media like CDs, DVDs, USB drives and flash media be procured, but the kit should also contain a laptop computer, DVD writer, flash media reader, and scan converter among other key items.
Using a laptop that also incorporates forensic video analysis software will enable
the user to verify the video evidence at the scene and provide enhanced
images at the time of recovery. Recovering digital video evidence is best accomplished when the equipment necessary to do the job right is available.

Finally standard operating procedures (SOPs) should be developed for the recovery
of digital video evidence. SOPs provide the steps to be taken when faced with a particular event or operation. Designing SOPs provides a consistent manner in which to extract the video evidence. With digital surveillance systems, a thoroughly designed SOP can describe the methodology in extracting the video evidence. It can also describe at what point the technical level of the procedure escalates dictating when to call in the person with more advanced training. With a plan in place, everyone knows what is expected and how to make that expectation reality. The recovery of digital video evidence will be approached in a uniform manner
with SOPs.

Although digital video surveillance systems show remendous potential and are becoming the de facto standard, ease of use and image quality is still a concern when compared to its analog cousin. It was a fairly straightforward operation in analog systems to eject the videotape from the timelapse recorder, capture the evidence, and apply a variety of tools to enhance the evidence. The digital counterparts are far more complex. Each recorder has different control buttons, features, and menus. Digital evidence is harder to access and sometimes cannot be readily played. The image quality may have been compromised by the effects of compression. Digital video surveillance systems have a long way to go in order to be considered superior in usage and image quality.

Until digital systems can be streamlined in functionality, features, and ease of operation, law enforcement must prepare for the complexities involved with digital video surveillance systems. Education should be provided to any person who handles
digital video evidence. The ability to recover digital video evidence regardless
of the method can be ensured through the procurement of the proper equipment. Providing a uniform manner in which to approach and recover video evidence through SOPs is also necessary. It is mandatory for law enforcement to have the education, equipment, and SOPs to capture the best evidence regardless of system type.

So the next time an armed robbery turns deadly and a digital video surveillance
system is found, what will be the experience of the investigators at the scene?
Will they be frustrated with their lack of knowledge on how to get the video evidence? Will they lack the equipment necessary to recover the video evidence? Will they have systematic procedures to assist them in determining what needs to be done to get the video evidence? Or will they have the education, equipment, and SOPs in
place to ensure they walk away with video evidence in hand for enhancement and analysis purposes? Make the move to today – learn the technology, get the equipment,
and form a plan.

More on the quality of digital video

In a digital world, image quality is often measured in pixels. Typically the more pixels there are in an image, the higher the image quality. Analog timelapse videotape cassettes record an image equivalent to a digital image of 720 by 480 pixels. Most digital video surveillance systems utilize the same camera technology as analog systems. The video signal from the camera is converted to digital in the DVR and stored onto a hard drive. The digital system may capture an area of 720 by 480 pixels but typically we see picture sizes of 640 by 480 pixels or 320 by 240 pixels. By comparing pixels per image in a digital system to an analog system, the image quality may sometimes be only equal or lower.

The tale with image quality does not stop at pixels per image. Digital surveillance systems use a process called compression to reduce the overall file size of the data used to represent the video. Compression removes details within the image. The result is an image that is of lesser quality but with the same overall idea. The advantage of compression is that the overall file size is reduced. Therefore extended periods of time can be stored on a single hard drive. The disadvantage is that image quality is not maintained through this compression process. Compression degrades quality. For
that reason, image quality of digital video surveillance systems is not vastly superior to analog systems.