Author Archives: Marco Fontani

Compression Artifacts: Hiding or Adding Details to the Scene

Dear friends, welcome to a new video pitfall post! This time we’re dealing with a very sneaky part of video analysis: can we trust what we see? Sometimes, distinguishing the real detail of an object from that of an artifact is not easy. Today’s post will review some of the most common video artifacts and their possible effect on your work.

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Timestamps: Not Always Showing the Right Time

Dear friends, welcome to this week’s video evidence pitfall! In this post, we’re focusing on a crucial element of forensic video analysis: timestamps. Timestamps allow us to locate in time what’s shown in a recording, or reference an event to a specific moment in time. Although virtually all surveillance systems do record timestamps, you should be aware of several pitfalls in accessing and interpreting them, so keep reading!

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Receiving Video Evidence: Usually It’s Not the Original

Dear friends, welcome to another video pitfalls pill! Today’s post concludes our mini-series about using the “best possible evidence.” In the previous weeks, we always assumed you had control from the beginning. Today, we focus on a different yet widespread scenario: you receive the “evidence” from someone else and are asked to work on that. Want to know the undercover pitfalls in this situation? Just keep reading!

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Screen Capture: It’s Not the Evidence, It’s a Video of the Evidence

Dear friends, welcome! Here we are with one more post for the “best possible evidence” mini-series. In the past two weeks, we’ve seen that you should not film the display and that proprietary players often alter the original pixels. Today, we’ll close this mini-series talking about screen capture. We’ll see that, while being much better than filming, this approach still has its issues and should be used only as a last resort. Keep reading!

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Proprietary CCTV/DVR Players: Often Not Showing the Original Pixels

Dear friends, welcome! This week’s post continues the “best possible evidence” mini-series. Last week, we showed why filming the display is not good. This week, we address a related topic: can we trust proprietary players? You’ll be surprised by the number of pitfalls hidden in the bare playback of a surveillance video, so keep reading!

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Cell Phone Snaps: Bad Quality and Reliability

Dear friends, welcome to your weekly dose of fear! Starting from today, we’ll be addressing a fundamental issue, perhaps the most important in your video forensic workflow: using the best possible evidence. We’ll dedicate some posts to this important topic, covering the various pitfalls you may encounter. Today, we’ll see why using a mobile phone (or even a professional camera on a tripod) to capture footage is, well, not recommended. Keep reading!

Issue: Filming the Display Creates Awful Footage

Let’s start with a quote from one of our esteemed users:

The jobs I manage never get that far as we work with appalling quality footage in the vague hope of securing a conviction.

Well, it’s certainly true that, sometimes, there’s not much we can do. But in many cases, the “appalling quality” is due to how the evidence video has been acquired, or how the working copy has been produced. Let’s go practical with an example. Can you get this license plate?

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Color Fidelity: It’s Hard to Objectively Evaluate Colors on Video

Welcome to this week’s Video Evidence Pitfalls post, dear friends! Today we’re dealing with the reliability of colors in CCTV footage (and with any kind of digital images in general). Colors are an essential part of human perception, but can often be misleading in surveillance footage. Keep reading to find out why!

Issue: Colors Are Often Unreliable in CCTV Footage

As part of an ATM fraud robbery investigation, you are reviewing footage from two cameras in the same area. This is the image of the suspect as he walks away from the ATM.

He’s suspected of having visited another ATM of a bank nearby. So you review the footage of that camera as well, but… you don’t find anyone with a blue jacket and beanie hat. After syncing the clocks and checking frame by frame, you realize that it could be him:

But you also realize you will have a hard time convincing anyone about it. Why are the colors completely different?

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Playback Speed: If the Video Plays Too Fast or Too Slow, It Can Affect the Interpretation of the Events

Dear friends, welcome to our weekly Video Pitfalls post! Last week, we talked about the importance of a video’s time resolution (recording frame rate). Today, we’re dealing with playback speed, which is tightly related and also very important. Keep reading to find out why!

Issue: the same thing looks different at a different playback speed

As part of a burglary investigation, you are reviewing some CCTV footage of a parking lot. At some point, there’s an orange car that seems to act a bit suspiciously — it runs in one direction, then possibly realizes there’s no exit, and rapidly turns back. You even manage to see that the driver at the wheel acts quickly like he/she’s in a rush. Could that car be worth focusing on?

Notice that we are essentially basing the decision on how much of a rush the driver seems to be in. But what if the video played like this?

Everything is the same except for the speed: now the driver seems to be someone who just took a wrong turn and quietly turns back. And so the question now is: which of the videos (if any!) is an accurate representation of the actual event?

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Dealing with Deepfakes

“SEEING IS BELIEVING.” Or, rather, that’s what we used to say. Since the beginning of time, seeing a fact or a piece of news depicted in an image was far more compelling than reading it, let alone hearing about it from someone else. This power of visual content probably stemmed from its immediacy: looking at a picture takes less effort and training than reading text, or even listening to words. Then, the advent of photography brought an additional flavor of undisputable objectivity. Thanks to photography, pictures could be used as a reliable recording of events. Looking closer, however, it turns out that photographs have been faked since shortly after their invention. One of the most famous examples of historical hoaxes, dating back to the late 1860s, is Abraham Lincoln’s head spliced over John Calhoun’s body, and cleverly so. (Note: Click here to read the full hoax description on hoaxes.org.)


Politics was indeed an important driver for image manipulation throughout the years, as witnessed by many fake pictures created to serve leaders of democracies and tyrannies. We have photos of the Italian dictator, Benito Mussolini, proudly sitting on a horse that was held by an ostler (the latter promptly erased), photos of Joseph Stalin where some subjects were removed after they fell in disgrace, and so on. All these pictures were “fake”, in the sense that they were not an accurate representation of what they purported to show.

Of course, creating hoaxes with good, old-fashioned analog pictures was not something everyone could do. It took proper tools, training, and lots of time. Then, digital photography arrived, which was soon followed by digital image manipulation software and, a few years later, digital image sharing platforms. With advanced image editing solutions available at affordable prices—or even for free—there was a boom in the possibilities of creating fake pictures. Of course, you still needed suitable training and time to obtain professional results, but this was nothing compared to working with film.

In the last couple of years, we have witnessed a revolution in the manipulation of images: “deepfakes”. A deepfake is a fake image or video generated with the aid of a deep artificial neural network. It may involve changing a person’s face with someone else’s face (so-called “face-swaps”), changing what a subject is saying (“lip-sync” fakes), or even changing the words and movements of someone’s head so that they are like a puppet, or guided actor (“re-enactment”). But how is this achieved? What are these “deep artificial neural Networks”? How can we fight deepfakes?

In this article, published in the Evidence Technology Magazine, we’ll try to address these questions and bring some order to all of this.

Low Frame Rate: If You Don’t See It, It Doesn’t Mean It Didn’t Happen

Dear friends, welcome to this week’s video pitfalls post! When thinking of “video resolution”, we normally recall possible pixel matrix sizes (640×480, 1920×1080, and so on). This is the spatial resolution. A video however has a temporal dimension as well, with the ‘tempo’ relating to the speed at which the frames are captured and then presented. In many cases, this can be more important than spatial resolution. For this reason, we will dedicate this and the next post to this subject. Today, we deal with the recording frame rate, while next week we’ll talk about the playback speed.

Issue: If the recording frame rate is low, you are missing information

You are called to a bar where a scuffle just took place. Upon arrival, you listen to all the various witness and victim accounts and then the bar owner shows you the CCTV. This is what you view (we’re using a video from the “UnarmedcombatOnline” YouTube channel).

No matter how many times you play the video, you hardly understand how the guy with a black sweatshirt turns from standing to laying on the ground, and it does not match some eye-witness accounts. You decide to acquire the evidence (in a forensic manner) utilizing the device’s USB Export function.  Back at the station, or on your laptop, you view the evidence in Amped Replay. Carefully navigating the frames allows you to check thoroughly all the available information in the recording. By scrolling the gallery below, you’ll notice that in frame 2 the guy is standing, and in frame 3 he’s grounded. What happened in between? We don’t know.

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