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Sunday, November 1, 2015

Locard's Exchange Principle

Edmond Locard (1877–1966) studied law at the Institute of Legal Medicine in Lyon, France, and worked subsequently as an assistant to the forensic pioneer Alexandre Lacassagne prior to directing the forensic laboratory in Lyon, France. Locard's techniques proved useful to the French Secret Service during World War I (1914–1918), when Locard was able to determine where soldiers and prisoners had died by examining the stains on their uniforms.

Like Hans Gross and Alphonse Bertillon before him, Locard advocated the application of scientific methods and logic to criminal investigation and identification. Locard's work formed the basis for what is widely regarded as a cornerstone of the forensic sciences, Locard's Exchange Principle, which states that with contact between two items, there will be an exchange. It was Locard's assertion that when any person comes into contact with an object or another person, a cross-transfer of physical evidence occurs. By recognizing, documenting, and examining the nature and extent of this evidentiary exchange, Locard observed that criminals could be associated with particular locations, items of evidence, and victims. The detection of the exchanged materials is interpreted to mean that the two objects were in contact. This is the cause and effect principle reversed; the effect is observed and the cause is concluded.

Crime reconstruction involves examining the available physical evidence, those materials left at or removed from the scene, victim, or offender, for example hairs, fibers, and soil, as well as fingerprints, footprints, genetic markers (DNA), handwriting, video, audio, and images... These forensically established contacts are then considered in light of available and reliable witness, the victim, and a suspect's statements. From this, theories regarding the circumstances of the crime can be generated and falsified by logically applying the information of the established facts of the case.

Locard's publications make no mention of an "exchange principle," although he did make the observation "Il est impossible au malfaiteur d'agir avec l'intensité que suppose l'action criminelle sans laisser des traces de son passage." (It is impossible for a criminal to act, especially considering the intensity of a crime, without leaving traces of this presence.). The term "principle of exchange" first appears in Police and Crime-Detection, in 1940, and was adapted from Locard's observations.

Saturday, August 15, 2015

End of an era

It's with a touch of sadness and regret that I must end my run as your humble blogger. I will leave this site up for as long as Google allows, to serve as a reference. But no new posts will appear.

All the best and thanks.


Thursday, August 13, 2015

Error U44M1l210 - Adobe Creative Cloud Apps

I can't update the Adobe Creative Cloud apps on my MacBook Air. I keep getting the same error. I've been to the forums. Here's one thread full of frustrated customers. Here's another with a stupid solution.

Adobe's support has gone down the tubes over the years. SO GLAD I don't need the update right now. SO GLAD I use Amped FIVE for all of my forensic work now.

Monday, July 27, 2015

Prof. Alexander "Sandy" Allan

In the years since my book was published, people have asked about the dedication page. Who is "Sandy?" Professor Alexander "Sandy" Allan was my great uncle, my inspiration, and the guide to my academic and professional life. He passed away on July 10th.

Sandy Allan
October 21, 1926 - July 10, 2015

Sandy passed away at home, aged 88. Sandy was predeceased by his beloved wife, Marguerite (Gunton). He was a much-loved father to Cynthia Norrie (Alastair) and to Paul (Maggie) and a devoted grandfather to Elizabeth, Kate and Michael Allan. He was also the last survivor of all his siblings, Jean ("Bet"), Jim and Jack. Sandy was a passionate engineer. His career began with the Defence Research Board of Canada in 1950. In 1958 he became a Professor of Mechanical Engineering at the University of Toronto and for the next 29 years he inspired many students with his hands-on, practical approach to education. In 1970 Sandy was retained as a consultant in a high profile motor vehicle accident lawsuit that ultimately lead to a successful second career as a consulting engineer. He later founded Alexander Allan Engineering Services where he became an acknowledged expert in the reconstruction of motor-vehicular accidents. Sandy was born and raised in the east end of Toronto where he attended Danforth Collegiate and Technical Institute. He earned both an undergraduate degree (1949) and a Masters Degree (1953) in Applied Science at the University of Toronto. Always generous with his time and many talents, Sandy frequently found himself called upon by both family and friends to build something or to fix something which he always did with focus and determination. Sandy had a particular talent for photography and carpentry. Evidence of his wood-working skill can be found in the homes of family and friends throughout Ontario. While he enjoyed a long retirement, Sandy suffered a stroke in 2004 and had been confined to a wheelchair for nearly 12 years; however, he continued to pursue an active life of the mind and pursued interests in science, technology and business.

My first recollection of "Uncle Sandy" was when I was five years old. He was in town to visit us and my grandmother, his older sister. It was 1976 and Toronto had just acquired an MLB franchise. He came with a bunch of Blue Jays swag; hats, jerseys, pennants, etc. Living in SoCal, we became instant Blue Jays fans. I still am.

He told stories about his travels and his work. He was, at the time, about how old I am now. I remembered thinking, people pay him to do the things he loves to do, pay him to travel around and have a great time doing it. Wow. This is what I want to do. And so, through a long and circuitous path, I set about to do it.

Words can not adequately express the feelings that result from the loss of one such as my Uncle Sandy, and I've been at a loss for words as of late.

Soft and safe to thee, be thy resting-place!
Bright and glorious be thy rising from it!

Thursday, July 2, 2015

Spready joins Amped Software

Amped Software just announced that David Spreadborough, aka Spready, has joined their team.

Awesome news. Congrats to Spready and to Amped Software.

Thursday, June 25, 2015

Discovery issues with certain kinds of images

An intersting question came in regarding a problem often encountered by LE folks processing / redacting CP images for court. Obviously, you don't want to process them one at a time when there are hundreds of images to redact. The question was tossed around and here's a simple way to do it in FIVE courtesy of our friends at Amped Software.

  • Open a sequence of images (Load>Sequence Loader)
  • Redact by blackening the whole image (Presentation>Hide Selection), then choose blacken at 100%, then change the shape from round to square, then on the “selection” tab, click and then choose “whole image” from the dropdown.
  • Export the redacted images as another sequence (Write>Sequence Writer). Change the file name / location to be what you need it to be.
  • Generate your report (Project>Generate Report.
I know not many folks work with CP. I hope this helps.

Wednesday, June 24, 2015

Quality issues with body worn cameras

Amped Software's latest blog post features an article on the various quality issues associated with body worn camera recordings, and how their software can be used to fix them all.

Check it out here.

Thursday, June 11, 2015

Rolling Shutter Effect

"Rolling shutter is a method of image capture in which a still picture (in a still camera) or each frame of a video (in a video camera) is captured not by taking a snapshot of the entire scene at single instant in time but rather by scanning across the scene rapidly, either vertically or horizontally. In other words, not all parts of the image of the scene are recorded at exactly the same instant. (Though, during playback, the entire image of the scene is displayed at once, as if it represents a single instant in time.) This produces predictable distortions of fast-moving objects or rapid flashes of light. This is in contrast with "global shutter" in which the entire frame is captured at the same instant.

The "Rolling Shutter" can be either mechanical or electronic. The advantage of this method is that the image sensor can continue to gather photons during the acquisition process, thus effectively increasing sensitivity. It is found on many digital still and video cameras using CMOS sensors. The effect is most noticeable when imaging extreme conditions of motion or the fast flashing of light. While some CMOS sensors use a global shutter, the majority found in the consumer market utilize a rolling shutter.

CCDs (charge-coupled devices) are alternatives to CMOS sensors, which are generally more sensitive and more expensive. CCD-based cameras often use global shutters, which take a snapshot representing a single instant in time and therefore do not suffer from the motion artifacts caused by rolling shutters."

Tuesday, June 2, 2015

File systems, thumb drives, and DVRs

I get a lot of help requests from LE employees trying to retrieve DME at crime scenes. Some of them work like this:

Officer: "I'm standing in front of the DVR. I'm trying to back-up the data but the DVR won't see my thumb drive. What am I doing wrong?"
Me: "What file system are you using on your thumb drive?"
Officer: "What do you mean?"

Officer: "I'm standing in front of the DVR. I'm trying to back-up the data and the DVR is asking if I want to format by USB stick. Should I click OK?"
Me: "Is the drive empty?
Officer: "I've got a bunch of case files on it."
Me: "Click cancel and get another drive."

I keep a bag of thumb drives of various sizes and formats. Some older systems won't accept a thumb drive with a capacity larger than 2gb formatted as FAT. Others won't accept anything larger than 4gb. However, 4gb is a nice size to carry as you'll want to move the files to WORM discs when you create the master evidentiary copy. Most people have DVD readers, so this bit of pre-file management will help you keep organized.

So, don't throw away those old jump drives. You may need them some day.

Friday, May 22, 2015

SWGDE Response to the Termination of SWGIT

Posted on behalf of James Darnell, SWGDE Chair:

The recent announcement that the Scientific Working Group on Imaging Technology (SWGIT) made the executive decision to cease operations was disappointing news to the members of the Scientific Working Group on Digital Evidence (SWGDE). In this exciting but challenging time of standardization efforts and quality assurance development, our sister SWG was a solid example of how people can contribute to an industry effort in addition to their normal work responsibilities. The SWGIT membership leaves an impressive legacy of numerous guidelines and best practices in the Forensic Video, Image Analysis, and Forensic Photography disciplines.

SWGDE was proud to work closely with SWGIT for many years. Together we produced several joint documents including the SWGDE/SWGIT Guidelines and Recommendations for Training, SWGDE/SWGIT Proficiency Test Program Guidelines, SWGDE/SWGIT Recommended Guidelines for Developing SOPs, and the SWGDE/SWGIT Digital & Multimedia Evidence Glossary. SWGDE is pleased to have had the opportunity to support SWGIT when we could, especially with joint meetings. SWGDE helped build and financially support the SWGIT website since its inception and will continue to do so.

In keeping with that tradition of cooperation and support, SWGDE will help continue the achievements of SWGIT's membership by inviting them to participate in three new standing committees created to address video, photography, and image forensics. We also invited them to bring any unfinished work items, topics and agenda items that need addressing, but it will ultimately be up to the new committee members to decide their agenda and priorities.

SWGDE's mission is to bring together organizations actively engaged in the field of digital and multimedia evidence in order to foster communication and cooperation as well as to ensure quality and consistency within the forensic community. So while it is difficult to see such a valuable member of our community dissolve, we hope that through our new committees, SWGDE will address the discipline specific needs formerly provided by SWGIT.

David Hallimore
SWGDE Outreach Committee Chair

Security - Safety Korea 2015

South Korea's big security convention is next week. Security - Safety Korea 2015 is sure to feature the latest and greatest of Korean CCTV tech. This means that you can expect the usual flood of new Korean DVRs at retail outlets. It also means new codecs, new players, and (hopefully) some DVRs that will feature faster I/O options. Nothing's worse than an HD recorder with USB 1 output.

Monday, May 18, 2015

TASER to Acquire MediaSolv Corporation to Broaden Digital Evidence Management Solutions For Law Enforcement

Taser recently made an incredibly smart move, they acquired MediaSolv. This solves a serious issue for them and gives their customers an option of either cloud storage (Evidence.com) or local evidence management (MediaSolv Commander).

Here's the announcement.

Monday, May 11, 2015

Leaving unpowered SSDs in a warm room can kill your data fast

Many of us are in the business of collecting data from crime scenes. Some actually collect hard drives. This article from PCWorld highlights a new risk associated with unpowered SSD drives.

"A new research presentation shows that solid state drives can lose data over time if they aren’t powered on, especially in warmer environments. A powered-off drive in 104 degrees Fahrenheit may start seeing data loss after a couple of weeks.

The information comes from Seagate’s Alvin Cox, who as part of a presentation to the Joint Electron Device Engineering Council (JEDEC). Though the presentation is a couple months old, it was recently picked up by ZDNet, Slashdot and other sites.

Cox’s presentation shows basic performance requirements for both consumer and enterprise SSDs. It notes that consumer SSDs, when powered-off in 86 degrees Fahrenheit (30 degrees Celcius), should retain data for about a year. Bumping up the temperature by 9 degrees Fahrenheit (5 degrees Celcius) reduces the time of data retention by half. Store your SSD in 131 degree heat, and it might start losing data after a couple of days ..."

Click here for the whole story.

Thursday, May 7, 2015

Termination of SWGIT

This just in from SWGIT:

The Scientific Working Group on Imaging Technology (SWGIT) would like to thank the forensic community for the continued support, involvement, and participation in making this group and the documents we have provided over the last 18 years so very successful. The mission of the SWGIT has been to facilitate the integration of imaging technologies and systems within the criminal justice system (CJS) by providing best practices and guidelines for the capture, storage, processing, analysis, transmission, output, and archival of digital evidence. This mission has served our community well since the inception of the group in 1997. The SWGIT documents have been essential to developing laboratory and law enforcement best practices and guidelines across the United States as well as internationally. The documents have been used to demonstrate reliable scientific principles and methods in court and Daubert hearings.

The current economic climate has impacted the continued work of SWGIT. Due to a lack of funding revenue, SWGIT has made the decision to terminate operations. SWGIT’s website and social media will remain available as a continued valuable resource for all questions involving Forensic Video, Image Analysis, and Forensic Photography.
SWGIT documents will remain in effect and available on the SWGIT website, www.swgit.org. SWGIT has addressed concerns important to all members of the community including first responders, laboratory examiners, and managers of criminal justice organizations. Our website contains more than 20 recommendations and guidelines detailing procedures for digital photography, video and image processing, CCTV installations, documentation of image enhancement, and several other topics important in the current forensic environment. SWGIT was instrumental in the publication of two of our documents as ASTM standards, “Standard Guide for Image Processing” and “Standard Terminology for Digital and Multimedia Evidence Examination.”

As the forensic community moves forward, a goal of SWGIT is to continue to engage the entire law enforcement imaging community in the development of guidelines, best practices, and standards. In remaining true to that goal, SWGIT strongly encourages the members of our forensic disciplines to continue to support other professional groups that strive to provide such information.

SWGIT will continue to have an active web presence at www.swgit.org and on social media. Please see the social media links provided on our website.

Thank you again for making SWGIT such a long-standing success.

Melody Buba
Federal Bureau of Investigation

Cory Winar
Vice Chair
Eugene Police Department

Friday, May 1, 2015

How Are States Going to Pay for Those Police Body Cameras?

This just in from Governing.com: "The Police Executive Research Forum survey found most agencies spent between $800 and $1,200 per camera to purchase them, a daunting price tag for departments already strapped for cash.

But it is the ongoing costs that are the real challenge. The New Orleans Police Department plans to purchase 350 body cameras, but is budgeting $1.2 million over five years, mostly for data storage. Other departments, the police forum found, expect to spend $2 million for a few years of data storage.

In Iowa, the Des Moines Police Department is looking for $300,000 just to start a body camera program. Duluth, Minnesota’s initial $5,000 purchase of 84 cameras ballooned to about $78,000 for licensing and data storage. Last year, Duluth’s police budget was $19.1 million, while Des Moines spent more than $59 million on its police force.

Many states are debating the issues that surround police cameras without tackling the funding question, said Richard Williams, a criminal justice policy specialist with the NCSL. In many instances, he said, lawmakers are focused how long departments should have to keep video, and if or when recordings should be made public.

Miller, with the Police Executive Research Forum, said those issues are important, but that for police departments, cost is the overriding concern.

Officers could potentially record millions of videos a year, any number of which could be used as part of a criminal proceeding, a public records request or for another official purpose. The cost of downloading, logging, handling and storing all that video can be staggering.

“Most of the agencies that we worked with say the biggest issue is the backend data storage,” she said. “It can cost hundreds of thousands of dollars to store video each year.”

Costs were a stumbling block in Utah this year, where state lawmakers debated but didn’t pass body camera legislation. Meanwhile, some departments around the state are using the technology — and trying to meet the costs associated with it.

In Clearfield, Utah, a city of about 30,000 located 30 miles north of Salt Lake City, the police department has been using body cameras since 2010. But recently, data storage problems came to a head, and for a few weeks, the department was forced to use DVDs to store video because it ran out of computer server space.

“The more you use them, the more storage it takes, and the costs increase,” said Mike Stenquist, an assistant chief. “The public wants more, it also costs more. It creates a lot of problems.”

It’s not likely to get any better either, Stenquist said. Years ago, the department used older model cameras that needed to be recharged frequently and could only record two hours of video at a time, meaning officers had to return to the office frequently to download any recordings.

New models last longer and have greater storage capacity, he said. But now there’s another problem: The newer cameras record high-definition video, which means the video files are much larger, a reality that contributed to the department’s recent data crunch.

“The data just builds up,” Stenquist said. “Now that we have better cameras that record through a whole shift, it’s taking three or four times the data storage.”

Between cost concerns and public access questions, Stenquist said, it’s probably inevitable that state lawmakers will have to step in.

“It’s just become pretty muddy about what’s going to happen in the future,” he said. “There’s a lot of work to be done.”

Click here to read the whole story.

Tuesday, April 28, 2015

New NVIDIA drivers will no longer support older CUDA GPUs

This just in from Adobe: "Just to alert you, NVIDIA is starting to discontinue CUDA support for some older GPUs in their new driver releases. If you are still using one of these older cards, and need GPU support for Adobe applications, do not update your drivers while you look into a purchasing a new card.

If you need to reinstall NVIDIA drivers, see this web page."

Wednesday, April 22, 2015

a little humor

A photon checks into a hotel and the bellhop asks him if he has any luggage.

The photon replies, “No, I’m traveling light.”

Monday, April 20, 2015

Police Cameras Bring Problems of Their Own

This just in from the Wall Street Journal: "As more police agencies equip officers with body cameras in response to public pressure, authorities are discovering they create problems of their own: how to analyze, process and store the mountains of video each camera generates.

Prosecutors in northern Colorado recently spent hours poring over a dozen videos captured by police wearing cameras. The case? An arrest for drunk and disorderly conduct.

Clifford Riedel, Larimer County’s district attorney, said his office has been overwhelmed with footage from the 60 body cameras the Fort Collins Police Department uses, and will need to hire an additional technician to sort through it all. “There are just huge amounts of data being generated from cameras,” said Mr. Riedel. “It used to be that video on a case was the exception. Now it’s the rule.”

The movement gained new intensity after the police shooting last week of a fleeing man in South Carolina. While many experts inside and outside of law enforcement agree that body cameras—clipped to officers’ uniforms or glasses—help increase police transparency and may even improve police behavior, police departments and prosecutors are struggling with how to sift through, preserve and share the visual evidence.

On top of that, agencies need policies and personnel to respond to requests from journalists and the public to release video under freedom-of-information requests.

“The vast majority of places are still trying to figure this out,” said Michael White, a professor of criminology at Arizona State University who wrote a Justice Department report on body cameras.

Dr. White estimates that between 4,000 and 6,000 U.S. police departments, out of about 18,000 nationally, use body cameras. Officers generally turn them on when stopping a driver or responding to an incident.

Some departments use body cameras in addition to dashboard ones that have become common at many agencies, but result in less-useful footage because much police action takes place away from their vehicles. Body cameras—which cost hundreds of dollars each—typically result in much more video for departments to handle.

The push to require body cameras intensified nationally after last August’s shooting of Michael Brown, a black 18-year-old, by a white police officer in Ferguson, Mo. This week, after a bystander’s cellphone video surfaced showing a white South Carolina policeman fatally shooting an unarmed black man in his back, several prominent state lawmakers voice support for a bill to require all officers to wear cameras.

But the cost has given some officials pause, said Lindsay Miller, senior research associate at the Police Executive Research Forum and co-author of a Justice Department report on the topic. “The cameras themselves aren’t overly expensive, but the years and years of data storage you’re going to deal with—that can definitely be cost-prohibitive,” said Ms. Miller.

Many departments keep inconsequential video for 30 to 60 days. But if the footage is evidence in a criminal case, it must be kept longer; most states require that video in a homicide case be kept indefinitely, she said. Ms. Miller said an emerging consensus is that the benefits outweigh the costs. In limited studies, the cameras have shown promise in reducing use of force by police and citizen complaints—and that can save money spent investigating complaints and settling lawsuits, she said ..."

Keep reading at WSJ.com.

Tuesday, April 14, 2015

Correct Fisheye Distortion in FIVE

I've seen a lot of ADT installations using fisheye lenses lately. ADT must be having a sales promotion or something.

One of the updates to FIVE in the last year is the Correct Fisheye filter, found in the Edit filter group.

In the past, I would use the Undistort filter, but Correct Fisheye works a lot better / easier / faster on these low-end fisheye lenses I've been seeing.

In the case of the "full-frame" (180º) fisheye lenses in the ADT installations, I've found that Orthographic works the best. This isn't because ADT has been forthcoming with information about the mapping function of their chosen lenses. It's mainly been through my testing each function. You won't likely get information on the manufacturer's chosen mapping function.

As a side note, for the "circular fisheye" top-down (360º) lenses, use the Unroll filter for better results.

Back to the ADT cameras, here's the before/after image (Presentation>Compare Original). On the left is the original image and on the right is the corrected version. Correct Fisheye did a very good job in just two clicks of the mouse.


Monday, April 13, 2015

It looks like the transition to Amazon.com is finished and my book, Forensic Photoshop, is now available there exclusively. Paperback and hardcover options are both available for immediate shipping.

As I've noted in the past, the book isn't based on a particular version of Photoshop. It's a workflow book ... what to do when, and why. As such, it's still relevant and informative for those still using Photoshop in their forensic work.

Thanks again for your continued support.

Friday, April 10, 2015

What's next for Adobe Audition CC?

Adobe has begun to release details about the upcoming changes to their Creative Cloud products. Click here to find out what's coming next in Adobe Audition CC.

Thursday, April 9, 2015

A bite mark matching advocacy group just conducted a study that discredits bite mark evidence

Here's an interesting article from the Washington Post about Forensic Odontology.

Check out this quote, "the problem with bite mark analysis was never the lack of a flow chart. The problem is that there has never been any real scientific research to support its two main underlying premises — that human dentition is unique, and that human skin is capable of registering and recording that uniqueness in a useful way. And the research that has been done strongly suggests those two premises are not true." Ouch!

Read the whole article here.

Wednesday, April 8, 2015

Coursera courses reviewed

Last week, I finished the Coursera course, Visual Perception and the Brain. This course was taught by Dale Purves, MD, of Duke University and is one of the growing number of on-line non-credit courses offered by leading universities and noted professors around the world.

I would recommend that DME analysts put this course on their to-do lists and watch for it to be offered again. There's a lot of good information delivered as part of the class.

That being said, if you've never taken an on-line university level course you may have some trouble with the format. You watch the video of each section's lecture. You're free to download and save it locally. You can also download and save the slides and a fairly accurate transcript of the lecture. There's an expectation that you'll dive in a little deeper and study each section's topic on your own prior to taking each section's test. The test questions aren't written directly from the lecture / slides and assume that you've done a bit of extra reading in order to gain a deeper understanding of the week's topic.

Coursera has a lot of classes available for free. In this world of shrinking budgets and doing more with less, you can't beat free classes.

Monday, April 6, 2015

Recovering image data from JPEG file fragments

This interesting paper was recently published by SPIE. SPIE is the international society of optics and photonics.

"A new technique for recovering fragmented data files can retrieve elements of a JPEG compressed image even when the file's header is unavailable."

"The most basic task of any file system is to manage and organize data in a storage volume. Each file in the store is allocated a list of blocks (the basic unit of access), and when we access a file, the system retrieves the data in sequence from the list. Correspondingly, removing the relevant entry deletes the item (note that in most systems, deleting simply means that data is overwritten over time by newly saved files, rather than actually removed). Figure 1 depicts the layout of files distributed across blocks of a storage medium, and provides a simplified view of the data structure used to track allocated blocks. When the information for a volume is corrupt or missing, it is only possible to recover files by analyzing the fragmented raw data, a process known as file carving."

"Today, file-carving tools play an important role in digital forensic investigations, where analyzing deleted files and salvaging data from damaged and faulty media are common procedures. However, when files are encoded and compressed (as with most multimedia files), recovery is dependent on the availability of the file header, which includes all the decoding parameters. If a file is partially intact with its header deleted, common carving techniques cannot recover any data. Here, we describe an algorithm1 that advances the latest developments in JPEG carving by introducing the ability to recover file fragments when the associated header is missing.

There are two main challenges associated with file carving. The first is the inability to lay out data blocks contiguously on the storage, as in the case of files b and f in Figure 1. Repeated execution of file operations, such as addition, deletion, and modification of files, over time leads to fragmentation of available free storage space. As a result, the newly generated files need to be broken into several parts to fit into the available unallocated blocks. Figure 1 illustrates this phenomenon, where files a and c are separated into two pieces. Even the new solid-state drives (which use integrated circuits, rather than disks, to store data) are susceptible to this phenomenon as they are designed to emulate the interface characteristics of hard disk drives.

The second challenge to successful file carving is that interpreting binary-formatted data requires the use of decoders, without which a block of data will reveal little or no information about the content of a file.

There has been significant recent progress in carving JPEG files, which are the most widely adopted still image compression standard today and commonly the subject of forensic investigations.2–6However, techniques for JPEG recovery still assume that a file header is always present. Without the header, the usual techniques cannot recover any data, even though the rest of the file may be intact. For example, in Figure 1, the fragments of files d, e, and g were overwritten by files c and f. Recovering an arbitrary chunk of compressed image data without the matching encoding metadata essentially requires reconstructing a new file header, which at least requires knowledge of entropy coding parameters and quantization tables, methods used during compression for downsampling the color information and image dimensions."

Click here to continue reading this paper on SPIE's web site.

Friday, April 3, 2015

LEVA Job Classification and Wage Study Results

This just in from LEVA: "The following Job Classification and Wage Study was completed in March of 2015 as part of a position audit. The survey focuses on particular job duties and functions performed by various analysts, technicians, and those who in some way handle digital multimedia evidence.

All information contained in this report was volunteered by those who responded to the survey invitation, knowing that they fit the subject matter criteria. It is being shared with the Forensic Digital Multimedia Evidence community due to numerous requests for the information.

LEVA thanks those who responded with data for Jordan Huslig of the Grand Junction, CO PD Crime Lab to conduct the research and providing the findings. Nice job Jordan!"

Click here to read the result and/or access the raw data.

Thursday, April 2, 2015

How to: Open Exe Files on A Mac

I recently had an .Exe video file that wouldn't capture using any/all available PC tools. I tried Omnivore, FIVE, and a few others. Nothing. Thank God for my trusty old MacBook Pro.

Here's an old video tutorial that's still relevant. It demonstrates using Wine / WineBottler to re-bundle the file into something that the Mac will recognize.

Wine / WineBottler worked like a charm on my video. Then, I used iShowU to do the screen capture.

Sometimes folks can't/won't mess with executable files and require the files to be "converted." Not all of them play nice with our state of the art systems. It's nice to see that the old tricks still work.


Thursday, March 26, 2015

More S-FIVE news

This just in:

The S-FIVE project will organize an international workshop about Forensic Image and Video Enhancement on June 15-18, in Brussels, Belgium. The maximum number of participants to this workshop will be limited, but EU attendees can be partially funded by the Prevention of and Fight against Crime Programme, European Commission - Directorate-General Home Affairs (through the ENFSI Monopoly 2011 Programme).

The S-FIVE webpages will continue to evolve further, but:

More details on how to apply for (funded) participation to the workshop are now available via the S-FIVE project website.

The S-FIVE project team,

The S-FIVE project is a project funded by the Prevention of and Fight against Crime Programme;
European Commission - Directorate-General Home Affairs, through the European Network of Forensic Science Institutes (ENFSI) Monopoly 2011 programme "Improving Forensic Methodologies across Europe" (IFMAE).

Wednesday, March 25, 2015

Forensic Photoshop Book moves to Amazon

After many years of pushing up against the behemoth that is Amazon, my publisher and Amazon are finally at the point of reasonableness. Thus, it is with a bit of nervousness that I announce that my book, Forensic Photoshop, will be available for purchase exclusively on Amazon.com starting next week.

I realize that the book has been in print for quite a while. But, if you stop to consider that the way law enforcement uses Photoshop hasn't changed since the book came out ... it's still relevant. It's not a collection of tips and tricks. It's not based on a specific version of Photoshop. It's a book about workflow; and the workflow hasn't changed.

I appreciate all of the support. I never imagined that the book would do so well. Stay tuned for the official Amazon links to get your copy, if you haven't already.


Monday, March 23, 2015

Free web version of Signal Processing for Communications

I know folks like to build their libraries. But, it can get expensive. Recently, I came across this free web version of Prandoni & Vetterli's Signal Processing for Communications. They also have a PDF version available for free downloading. This page offers their reasoning for offering their text for free, along with a link if you'd care to donate to support their cause.


Friday, March 20, 2015

Draft law mandates CCTV use

Here's an interesting article from Kuwait City, "Cabinet OKs Law On Surveillance Cameras

KUWAIT CITY: The Council of Ministers has approved the draft law which has been submitted by the Deputy Prime Minister and Minister of Interior Sheikh Mohammad Al- Khalid for the installation of security surveillance cameras, reports Al-Anba daily.

The daily added, during the first phase 15 cameras will be installed at vital places and this exercise will be followed by the installation of cameras at other places as the need arises. According to the draft law, the owners of these so-called vital places will be obliged to install security cameras with a capacity of storing data for not less than 120 days.

The draft law stipulates three years imprisonment for any person found tampering with the recorded data by the surveillance cameras, for not saving the data or publishing any of the contents. Sources said what is recorded by these cameras shall be considered tangible proof in the event of any crime, assault or theft.

According to the draft law these cameras must also be installed at hotels, banks, and sports and cultural clubs, youth centers, entertainment centers such as recreational parks, shopping malls, commercial complexes, residential complexes, and banks, jewelry shops, jewelry stores, hospitals, clinics, and motels."

Notice the glaring omission? No hint about standards. You can't balance an equation by working just one side of the equal sign.

Thursday, March 19, 2015

Cyber CSI: the challenges of digital forensics

This just in from Richard Boddington at TheConversation.com: "Forensics is changing in the digital age, and the legal system is still catching up when it comes to properly employing digital evidence.

Broadly speaking, digital evidence is information found on a wide range of electronic devices that is useful in court because of its probative value. It’s like the digital equivalent of a fingerprint or a muddy boot.

However, digital evidence tendered in court often fails to meet the same high standards expected of more established forensics practices, particularly in ensuring the evidence is what it purports to be.

Technology changes evidence

This is not the first time that technology has impacted the way evidence is gathered and presented in courts. And it’s not the first time that there have been problems in the way new evidence is used ..."

To continue reading this article, click here.

Wednesday, March 18, 2015

S-FIVE Collaborative Exercise

I received the following invitation from the S-FIVE project team. They've asked that I share the information here.


Dear colleagues,

With this e-mail the S-FIVE project team wishes to invite you to participate to its:

Collaborative Exercise on Forensic Image and Video Enhancement.

The exercise consists of four subparts related to:
Image extraction, Focal and Motion Deblur, and Superresolution.

The final deadline for submission of results will be Fri., April 24.

Please feel free to forward this e-mail to any colleagues, tool vendors or academic contacts that may be interested in participating to this exercise.

The S-FIVE project team,

The S-FIVE project is a project funded by the Prevention of and Fight against Crime Programme;
European Commission - Directorate-General Home Affairs, through the European Network of Forensic Science Institutes (ENFSI) Monopoly 2011 programme “Improving Forensic Methodologies across Europe” (IFMAE).



Tuesday, March 17, 2015

Vehicle Examiner announcement from DME Forensicsis

The folks over at DME Forensics announced the impending beta of their newest adventure, Vehicle Examiner. It seems, from the announcement, that they've taken the Digital Automotive Image System and given the concept a bit of modernization. But, unlike the DIAS, I doubt that Vehicle Examiner will be free to law enforcement.

If you're interested in getting involved in their upcoming beta program, head over to the Vehicle Examiner web site and sign up for their newsletter.

Monday, March 16, 2015

Hertz puts cameras in its rental cars

Yes, you read the headline correctly. Hertz is putting cameras in their rental cars. But, they say that they have no plans to use them ... whatever that means.

Check out the details from Fusion.net.

Monday, March 9, 2015

Useful web based tools for doing math with photo and video features

This is a collection of web-based tools for calculations that are related to HDSLR video or cinema.

Friday, February 27, 2015

New training course available

New training course available:


This is a practical course on Amped Five.

Basic Forensic Multimedia Analysis with Amped FIVE Professional

Expectations and Goals:
Graduates will acquire basic level training in the techniques and skills necessary to perform examinations, clarifications, and analyses on digital multimedia evidence in a “forensic science” setting as well as to package, deliver, and present those findings in their local courtroom context. The focus on this course is practical usage of FIVE for forensic video and image analysis.

April 21-23, 2015

Memphis, Tennessee (Memphis PD is host agency)

Jim Hoerricks

For details or to sign up, click here. Seats are limited.
For any questions, email training@ampedsoftware.us or call (866) 547-0099 Ext. 101.

Thursday, February 26, 2015


This just in from SWGDE:

The Scientific Working Group on Digital Evidence (SWGDE) is pleased to announce the posting of the following four new draft documents for public review and comment at https://www.swgde.org/ documents/Released%20For% 20Public%20Comment

SWGDE Best Practices for the Recovery of Data from CCTV Digital Video Recorders (version 1.0)
SWGDE Mac OS X Tech Notes (version 1.2)
SWGDE Best Practices for Forensic Audio (revision 2.20)
SWGDE-SWGIT Glossary (version 2.8)
The draft "SWGDE Best Practices for Handling Damaged Mobile Devices" document released for public review and comment last September is still in draft status and remains open for comments: https://www.swgde.org/documents/Released%20For%20Public%20Comment/2014-09-08%20SWGDE%20Best%20Practices%20for%20Handling%20Damaged%20Mobile%20Devices

In accordance with SWGDE policy, draft documents will be posted for a minimum of 60 days for public comment. The first page of each draft document gives instructions on how to submit feedback to our Secretary via an email to secretary@swgde.org All feedback received prior to our next meeting in June 2015 will be reviewed by the appropriate subcommittee at that meeting.

At the conclusion of our last meeting, SWGDE voted to re-release the "SWGDE Establishing Confidence in Digital Forensic Results by Error Mitigation Analysis" document as an Approved version 1.5 making some minor grammatical/stylistic changes to it. However, as noted on the cover page of all our documents, "SWGDE encourages stakeholder participation in the preparation of documents. Suggestions for modifications are welcome and must be forwarded to the Secretary in writing at secretary@swgde.org"

All approved documents are available for download on the Current Documents page of the SWGDE website: https://www.swgde.org/ documents/Current%20Documents

We appreciate your participation as SWGDE continues its mission to bring together organizations actively engaged in the field of digital and multimedia evidence to foster communication and cooperation as well as ensuring quality and consistency within the forensic community. Anyone interested in receiving regular updates via email is encouraged to sign up for the SWGDE NewsBytes newsletter here: https://www.swgde.org/ newsletter/newsletterSignUp

Thank you,

David Hallimore
SWGDE Outreach Committee Chair

Monday, February 16, 2015

A big update to Amped FIVE

Amped Software announced a big update today. Along with some bug fixes, this update includes batch conversion, fish eye correction, and a few other niceties. If your support contract is current, use the feature in the Help menu to check for the latest update.


Friday, February 6, 2015

Image kernels explained visually

Here's a cool page that interactively demonstrates and explains how image kernels work.

Thursday, February 5, 2015

Facial recognition technology: How well does it work?

This just in from the BBC: "The revelation that police are holding a database of around 18 million mugshots has provoked an examination of the balance between civil liberties and catching criminals. But how effective is the technology?

Not as good as many people think, according to the Metropolitan Police officer in charge of the force's central forensic image team.

The system used by the force works by taking measurements between various points on people's faces in order to build up a picture of what they look like.

That is then matched against two databases - one holding mugshots taken of people who have been arrested and the other containing images from outside sources, such as CCTV.

'Super recognisers'

The main problem, Det Ch Insp Mick Neville told the BBC, is that most images are not of a good enough quality to produce any sort of match.

"With the vast majority of CCTV images, it will not work - in 18 months, we have had fewer than 10 hits."

That did not compare well against human performance. Mr Neville said he recently brought 90 "super recognisers" - people who are particularly adept at facial recognition - to Scotland Yard. "We had the best part of 300 IDs over three evenings," he said.

He added that, of the 4,000 images loaded on to the database following the 2011 London riots, only one has actually been matched to a person.

He was speaking after BBC Newsnight reported that many of the people whose images were being held by the police were innocent."

Continue reading the article by clicking here.

Wednesday, February 4, 2015

Coming soon

I've been working on some videos to help folks working in image analysis - some special cases - working with Amped FIVE and a few other tools. Stay tuned. I'll post them here and over on my YouTube channel.

If you have any special requests for techniques, or to highlight a particular tool/filter, let me know.

Wednesday, January 28, 2015

Thank you

I simply want to say thanks and I love you....
But please don't say you love me back, or that you love my page, or that I am great, or the best, or any of that, because then I will think that you think I am posting this just to get feedback and feel good about myself. Which isn't true. I just want to say I love you all very much and thank you for being a part of my life. And if you think: 'Well, how can she love me; she doesn't even know me?" Then you are likely Aspie, logical thinker, or don't read my blog. hehehe Anyhow, Thank you for being here.... 
I simply want to say thanks and I love you... 
(If you must post something, post a heart or smile)

Tuesday, January 20, 2015

Libavcodec bug threatens Windows XP VLC users

This just in from PCWorld.com:

"Watch out Windows XP diehards: if you run the open source media player VLC you may be vulnerable to malicious attacks. A bug discovered in November affecting VLC was recently made public on Full Disclosure, a security-focused mailing list.

The reported bug (dubbed CVE-2014-9597) allows a specially crafted video file with the FLV file extension opened in VLC 2.1.5 to corrupt memory. This could then allow the attacker to execute any code they want on the target machine. The vulnerability was tested on Windows XP SP3.

Why this matters: A bug that affects Windows XP may not be much of a worry for most users as XP’s user base has been slowly declining. But there are still some diehards holding on to the OS—around 18 percent of PC users worldwide run XP, according to Net Market Share.

While the bug apparently affects VLC users, it doesn’t appear to be an issue with VLC itself. Instead, the bug is caused by libavcodec, Jean-Baptiste Kempf, president of VideoLAN, the non-profit behind VLC, confirmed to PCWorld. Libavcodec is a third-party code library for encoding and decoding video and audio, maintained by FFmpeg. Kempf also said that he was unable to replicate the bug on Windows.

Whether or not the bug is a serious concern for users, the threat may not be long lived anyway. Kempf says the second release candidate for VLC version 2.2.0 fixes the issue. Concerned XP users can download and try out the release candidate from VideoLan."

Monday, January 19, 2015

Stop Believing TV’s Lies: The Real Truth About "Enhancing" Images

This just in from How-To-Geek: "You’ve seen it over and over. The FBI uses their advanced technology to “enhance” a blurry image, and find a villain’s face in the worst possible footage. Well, How-To Geek is calling their bluff. Read on to see why.

It’s one of the most common tropes in television and movies, but is there any possibility a government agency could really have the technology to find faces where there are only blurry pixels? We’ll make the argument that not only is it impossible with current technology, but it is very unlikely to ever be a technology we’ll ever see. Stick around to see us put this trope under the lenses of science and technology, and prove it wrong once and for all."

Click here to read the whole article.

Wednesday, January 14, 2015

The end of the CCTV era?

This just in from the BBC: "Twenty years ago the government backed a major expansion of the CCTV network - now funds are being cut and cameras shut off. Is the UK's CCTV boom over, asks Rachel Argyle.

In 1994, the Conservative government launched the Partners Against Crime initiative, with Home Secretary Michael Howard saying he was "absolutely convinced that CCTV has a major part to play in helping detect, and reduce crimes and to convict criminals".

The next year the CCTV Challenge Competition fund was started to encourage local authorities to set up surveillance schemes - the Home Office and local authorities invested £120m in CCTV systems within three years.

The UK has one of the largest CCTV networks in the world. But as cash-strapped councils look for cost-saving measures, the effectiveness of public CCTV is under scrutiny.

Dyfed-Powys police are set to cut funding to monitor CCTV following an independent report set up by Police and Crime Commissioner Christopher Salmon. The force covers over half of Wales and just under half a million people.

The report found that the removal of Powys Country Council CCTV did not result in a significant rise in crime or anti-social behaviour and there is little evidence that CCTV deters violent or alcohol-related crime. Salmon says the police will direct funds where the public want them, with "more bobbies on the beat".

These cuts are not an isolated case.

Cornwall was one of the first local authorities to cut their CCTV budget back in April 2011 - by £350,000. Denbighshire council will stop their funding and make a saving of £200,000 from 2016-17. Anglesey Council scrapped its CCTV altogether last year but following a successful charitable trust bid it will now be run by the island's five town councils. In Derby, 48 cameras in the city centre may be switched off.

Other areas are scaling back. Birmingham's 250 CCTV cameras will no longer be monitored around the clock and CCTV managers across the country face redundancy.

Police are under similar financial strain. Thames Valley Police could reduce its CCTV funding for the city from £225,000 annually, to as little as £50,000 by 2018.

A Freedom of Information request by Labour MP Gloria de Piero in March 2013, found that one in five councils had cut the number of CCTV cameras on the streets since the last election.

Supporters of CCTV point to the success of cameras in identifying suspects in high-profile cases, such as Robert Thompson and Jon Venables in the murder of toddler James Bulger, the Boston Marathon bombing, the London 7 July 2005 attacks and the 2011 UK riots. CCTV was crucial in the hunt for the Charlie Hebdo attackers.

But campaigners against CCTV believe it violates personal privacy and question its effectiveness.

"Britain's crime rate is not significantly lower than comparable countries that do not have such vast surveillance," says Emma Carr, director of Big Brother Watch.

The pressure group welcomes that budgetary restraints may make authorities look more closely at whether CCTV is really working. Carr adds: "Councils that reduce the number of ineffective CCTV cameras, diverting resources to where they will keep the public safer, are to be praised."

Charles Farrier, spokesperson for No CCTV, is a little more apprehensive. "The alleged cost-cutting is leading to a restructuring rather than a real reduction of camera surveillance." He points out that budget cuts will see others jump to the rescue. "Often the solutions offered are merging control rooms or taking the cameras out of the hands of democratic local bodies and into management by private companies driven by a profit motive," he added. He calls for an urgent public debate.

For some people, there's a more human alternative to fighting crime with increased CCTV. Farrier believes the solution lies in the findings of a 2013 report entitled Fortress Britain, published by the New Economics Foundation, which found that residents on an estate in London felt that "knowing people" was the key to creating trust.

"We no longer have park keepers, bus conductors, toilet attendants - people there to help act as a glue to hold the community together. Now we abdicate that responsibility to a machine. Surely instead of spending money on surveillance cameras it should be spent on proven strategies or encourage more people to walk, talk, and problem solve in their own communities?"

There has been much research into the effectiveness of CCTV as a crimefighting tool during the boom years.

A study entitled the Effects of Closed Circuit Television Surveillance on Crime (2008) found that CCTV schemes had little effect on crime deterrence, other than car crime ..."

Click here to keep reading the article.

Thursday, January 8, 2015

What's wrong with Photoshop?

Long time Photoshop users know that in order to get the most out of Photoshop, you'll need a pretty nice workstation with the "right" video card. Adobe explains why:

"The advantages of using a compatible video card (GPU) with Photoshop are better performance and access to more features. In this document, you will quickly find out everything you need to know about how Photoshop uses the Video Card (GPU) in your system including troubleshooting steps and features that have been recently updated to take advantage of the GPU.

This document provides a quick reference guide to video card usage in Photoshop. Some features require a compatible video card. If the video card or its driver is defective or unsupported, those features don’t work. Other features use the video card for acceleration; if the card or driver is defective, those features run slowly."

The GPU Sniffer

"To help guard against Photoshop crashes related to bad GPU hardware or drivers, Photoshop employs a small program called the GPU Sniffer. Every time Photoshop launches, Photoshop launches the sniffer. The sniffer runs rudimentary tests of the GPU and reports the results to Photoshop. If the sniffer crashes or reports a failure status to Photoshop, Photoshop doesn't use the GPU. The Use Graphics Hardware checkbox in the Performance panel of the Preferences is deselected and disabled.

The first time the sniffer fails, Photoshop displays a dialog indicating that it has detected a problem with the GPU. On subsequent launches, the dialog doesn't appear.

If you correct the problem, either by replacing the video card or by updating the driver, then the sniffer passes on the next launch. The Use Graphics Hardware checkbox is enabled and returned to its previous state (enabled or disabled)."

Wednesday, January 7, 2015

Mrs. Lincoln, I Presume? Well, as It Turns Out ...

You might have missed this one, but it's an interesting article on authentication and hoaxes.

"For 32 years, a portrait of a serene Mary Todd Lincoln hung in the governor’s mansion in Springfield, Ill., signed by Francis Bicknell Carpenter, a celebrated painter who lived at the White House for six months in 1864.

The story behind the picture was compelling: Mrs. Lincoln had Mr. Carpenter secretly paint her portrait as a surprise for the president, but he was assassinated before she had a chance to present it to him.

Now it turns out that both the portrait and the touching tale accompanying it are false.

The canvas, which was purchased by Abraham Lincoln’s descendants before being donated to the state’s historical library in the 1970s, was discovered to be a hoax when it was sent to a conservator for cleaning, said James M. Cornelius, the curator of the Lincoln library and museum in Springfield. The museum is planning to present its findings at a lecture on April 26.

“It was a scam to defraud the Lincoln family,” Mr. Cornelius said.

The Lincolns were not the only ones fooled. Ever since The New York Times announced the portrait’s discovery in 1929, on Feb. 12, Lincoln’s birthday, historians and the public have assumed it depicted Mary Todd Lincoln. It was reproduced in The Chicago Tribune and National Geographic, and versions of it still illustrate at least two biographies, including the latest paperback edition of Carl Sandburg’s 1932 “Mary Lincoln: Wife and Widow.”

In reality, the painting depicts an unknown woman and was created by an anonymous 19th-century artist, said Barry Bauman, the independent conservator who uncovered the fraud. The con, however, dates to the late 1920s, when the portrait was recast as that of Mrs. Lincoln, he said.

Mr. Bauman identifies the culprit behind the scam as Ludwig Pflum, who rechristened himself Lew Bloom and was given to the kind of self-invention that America became famous for during the industrial era. He worked as a jockey, circus clown, boxer and vaudevillian before settling on art collecting.

When he died less than a year after the painting’s public unveiling, an obituary in a Reading, Pa., newspaper noted that he “dabbled in oil paintings.” Apparently he dabbled more than anyone at the time realized ..."

Click here to keep reading the article.

Tuesday, January 6, 2015

Validation of forensic images for assurance of digital evidence integrity

Here's an interesting paper from Murdoch University in Australia.

"The reliability of digital evidence is an important consideration in legal cases requiring sound validation. To ensure its reliability, digital evidence requires the adoption of reliable processes for the acquisition, preservation, and analysis of digital data. To undertake these tasks, the courts expect digital forensic practitioners to possess specialised skills, experience, and use sound forensic tools and processes. The courts require that the reliability of digital evidence can be verified with supporting documentation; notably acquisition process logs and a chain of custody register, confirming that the process of recovering and protecting the evidence was based on sound scientific principles.

In typical cases the digital evidence has been ‘preserved’ in a special file or ‘container’ that has been declared to be secure on the basis that it is not possible to tamper with the contents of the container or the information supporting the contents (metadata) without this act being discovered. However, through the use of a freely available open source library, libewf, it has been discovered that the most commonly used forensic container format, Encase Evidence File Format, also known by its file extension .E01, can be manipulated to circumvent validation by forensic tools. This digital forensic container contains an embedded forensic image of the acquired device and metadata fields containing information about the data that was acquired, the circumstances of the acquisition, and details about the device from which the forensic image was acquired. It has been found that both the forensic image and the metadata associated with that image can be freely altered using simple file editors and open source software.

Exploiting these weaknesses within the Encase Evidence File format results in a forensic container that can be altered but fails to provide any evidence that this has occurred. In practice the original device is often unavailable, damaged, or otherwise unable to provide independent validation of the data held in the container. In such situations, it would be difficult, if not impossible, to determine which of two forensic containers held the original record of the evidence.
As part of a proof of concept, existing libewf code was manipulated to allow for legitimate metadata to be attached to a compromised and altered forensic image with recalculated hashes and data integrity checksums. Without incontrovertible records of the original data’s hash value, this manipulation might only be detected by an independent third party holding a copy of the original forensic container’s metadata and hashes for comparison. While hashes and metadata held by an interested party could also potentially be altered or declared unreliable, an uninterested party would be able to provide a more reliable set of hashes that could be used to validate the unaltered container.

In order to add to the body of knowledge supporting digital forensics as a scientific discipline this research has brought into question a fundamental assumption about the reliability of a fundamental method currently used to collect and validate digital evidence. Further research is required to determine the whether processes can be designed to enhance the detection of contaminated images."

Monday, January 5, 2015

A Coursera Course on Visual Perception Starts January 7th

This just in from the Scientific American:

"For those of you who don’t know what Coursera is, it’s one of several apps/websites that provides courses online. It’s an amazing system allowing for thousands of students to participate and view the same lectures. Such courses are generically referred to as MOOCs: Massive Open Online Courses. Coursera and its competitors, such as edX could potentially change the educational landscape by bringing the highest-quality education and lecturers to the general public, anywhere in the world, cheaply or even for free. No longer will aspiring students have to compete for an entire childhood before achieving entry into the world’s best universities to see these lectures: they can simply login to view the same lectures that are offered to the intelligentsia.

There’s a new 8-week course available on visual perception taught by Dale Purves of Duke University. It’s available for free and starts on January 7th, 2015. Purves’s approach to visual perception is exciting because it’s a bit different than the usual approach. Sensation and perception courses usually try to explain perception in terms of reconstructing the physical world. That is, the world exists, it has properties that can be measured with a visual system, and those measurements are then used to reconstruct a representation of the world in the brain based on those measurements. Visual illusions—where the perception doesn’t match the reality—in this model are errors in measurement: where the visual system gets it wrong. Sounds great, right? The problem is that our perception is not an accurate representation of the world (as Purves’s course will show), even when it could be based on the quality of the sensation. That is, our visual systems sometimes perceive illusions even when its measurements are accurate.

Purves considers that the visual system is instead working to solve an inverse problem… it’s trying to build a model of the world that will help the observer survive and reproduce (rather than to reconstruct the physical world accurately). What this means is that we can continue to work within the world (or, our model of the world) even in the absence of direct measurement. For example, to perceive the lightness of an object, the standard view of vision—as a reconstructive process—would be that the photoreceptors of the eye count photons that arrive from the object and report them so that we can reconstruct the object we’re viewing. That’s great except that—as Purves’s and his colleagues’ own lab work have perhaps shown best—lightness perception conflates the reflectance of the object (what color its surface is painted and how well it reflects photons that emanate from the light source), with the illumination of the object (how much light actually arrives from the light source), and transmittance of the object (how much light is either generated by the object directly… or travels through a through a transparent object from behind that object). All the visual system knows is the result of all of these object properties. But the object’s appearance nevertheless depends critically on knowing the contributions of all of these separate sources of photons. So what’s a brain to do? Purves’s view is that the visual system must guess at what the world looks like based on fitting its data to an internal, already-formed model of the world. Where does the model come from? From past empirical experience with the world. By experiencing and learning about objects throughout your life you adjust your model of the world to account for the frequency by which a given pattern of photoreceptor responses correlates to a given object. In this sense, genetically transmitted knowledge about the model also contribute to one’s empirical knowledge. So much of our model may be hardwired into our brains at birth, and your life tweaks your model as you go.

Many of Purves’s insights in visual science have correctly challenged the status quo and he is one of the finest phenomenologists in the world (a phenomenologist is a scientist who develops visual illusions for the purpose of drawing insight into visual processing in the brain). The image presented here is a terrific example. Notice that the orange and brown chips on the Rubik’s cube appear to be different colors that are reflecting different amounts of light (the orange chip is in the shade). Actually: the orange and brown chips are exactly the same color but are interpreted by your brain differently because they appear to have different levels of illumination. Don’t believe me? Print this image out on a printer, and cut the orange and brown chips out with scissors and compare them directly: they are exactly the same and only appear differently here due to their context."

So join me as a student in this course in January! It’s certain to be illuminating.

Friday, January 2, 2015

Why does Adobe Premiere Pro modify original footage/asset files

The following scenario was featured over on StackExchange.

  1. A colleague had given me a large 33Gb .mov for use in a project, I put this file on a backup drive.
  2. I made an identical copy of this 33Gb .mov file and placed it in a folder that I'd use to work on a Premiere Pro Project.
  3. I ran Adobe Premiere Pro CS6 and dragged in the 33Gb .mov file into the Sequence (imported it)
  4. Premiere Pro CS6 started conforming the file.
  5. After it had finished, I noticed that it's Modified Date was just now i.e different to the Modified Date on the original copy of the file on the backup drive (see step 1)
  6. I ran a BeyondCompare check between the .mov file on the backup drive (see step 1) and the one that the Premiere Pro project was using (step 2, 3) and Beyond Compare reported they were different.
I had initially thought it was unrelated file corruption of some kind, but I have checked this several times and got the same outcome, so it's definitely Premiere Pro deliberately modifying the file.

So I am puzzled: these are supposed to be the same file.

Why would there be a need for Adobe Premiere Pro to modify the footage? What does it do to the file? Would it not be better to create a separate file if necessary?

The answer to the user's question is featured here:

"It's all about this setting, "Write XMP ID To Files On Import" - which confirms that Adobe Premiere Pro is deliberately modifying the .mov file."

These posts give some background as to why having this setting enabled would be beneficial: one benefit being to be able to skip conforming files by matching the conformed file with the original using the embedded XMP tag:





Can you imagine what would happen on the witness stand if you didn't know this was happening to your files, and the opposing attorney asked you a series of very specific questions about your Premiere Pro (of Avid) work flow? OTS software does a lot of stuff to your files without telling you. That's the peril in using it for your forensic science work. It's yet another reason I've ditched the commercial editors in favor of software purpose built for our industry.

Thursday, January 1, 2015

Content analysis and confirmation bias

I was binging on Discovery Channel shows and flipping between football games today. BTW, happy new year.

I was amazed to watch as the people featured looked at pictures and video and described what they thought was in the video - a body, a tool, a hieroglyph, a UFO, and etc. I wasn't convinced. It seemed that all the pictures contained exactly what the producer wanted to see, but critical or scientifically based content analysis was never performed.

Confirmation bias refers to a type of selective thinking whereby one tends to notice and to look for what confirms one's beliefs, and to ignore, not look for, or undervalue the relevance of what contradicts one's beliefs.

As an example of this, most people reading this will look at the picture and think "egg and french fries (chips)." But, if you thought that when you saw the image, you'd be wrong. The photo above features apple slices and a half of a peach on yogurt.

And this is the problem when the untrained eye and brain engage in content analysis. They can both be fooled quite easily.