Author Archives: Marco Fontani

Perspective: Size Comparison May Be Tricky

Welcome, dear friends, ready for this week’s video evidence pitfall? Today we’re dealing with one video issue that often gets overlooked: perspective. It’s something we’re all familiar with, but in video analysis, it can play nasty tricks on you.

Issue: you shouldn’t compare the size of things at different depths

A robbery takes place and you get called. When you reach the shop, the owner runs at you yelling a classic statement: “I got him! I have a video!”. Indeed, there’s a video on the CCTV system and the suspect is there, as he walks into the shop (we’ve simulated a balaclava in the picture below). The face is disguised, but there’s good information about clothes. Then you think: well, I’m here in the shop, the suspect is close to the door, so why don’t I measure the height of the door to find out the height of the suspect?

Well, certainly measuring the door is an excellent step towards height analysis, but don’t take it too easy: that would just be the first step of a longer process. Indeed, you can’t directly compare the size of things at different depths because perspective makes farther things look smaller!

And it’s not just a matter of measurements: perspective affects the human view of an event. What you think you see may be affected by perspective: two planes in the sky may appear to be about to crash into each other when they are actually hundreds of feet apart. For CCTV, it may look as if an action or movement is one thing, but it is not in reality. Moreover, the perspective of the camera must be considered, and this is often very different from a witness perspective. Many cameras are high up and angled down, whereas witnesses will be at ground level and looking perhaps from a different angle. What one person sees may be very different from the camera’s view. 

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Lens Distortion: Cameras May Change the Shape of Things

Dear loyal readers welcome to this week’s video pitfall post! Today we continue our mission of shedding doubts on whether the aspect of things in your video is actually trustworthy. Last week, we showed the “stretching effect” that is often introduced by various aspect ratio issues. Today, we’re dealing with optical distortion.

Issue: Can you trust the shape of objects in a video?

Imagine you’re looking for a missing person. You ask the family for a recent picture, and they tell you, “Look, we have a video from our home camera. It shows her just before she gets out for the last time”. Hey, that could be useful, perhaps she still wears the same clothes and that would help the search. “Okay, we’ll take that video!”, you say. And here it is:

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Aspect Ratio: Be Sure Your Image Is Not Stretched in Either Direction

Dear friends, welcome to a new video pitfall post! Among the many visual clues, the shape and size of objects are quite important ones. However, we’ll see that in surveillance videos, they can quite often be misleading. Hold tight and keep reading!

Issue: Can you trust the proportions of objects in a video?

You get an urgent call. “They’ve just kidnapped a girl and fled in a car. We have a video from the pub next door!”. While you rush to the place, you’re already drafting the plan: you’ll look at the video and immediately start a search for the car based on the license plate… or at least the model!

Once you reach the place, they pass you a USB drive with a video file in it. You plug it in your laptop and play the video. Here’s the car.

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Infrared: Don’t Trust the Colors of Most CCTV Footage at Night

Dear friends, ready for this week’s Video Evidence Pitfall? Today we’re talking about infrared (IR) images, how they could be misleading, and some potential IR-related issues that may involve even “normal” videos. Keep reading!

Issue: you can’t trust any color in infrared images

How many times have you seen this kind of “washed out” image?

These are typical infrared images, and, as we will see, you should not use them to get any color information. To convince you, let me show you a couple of pictures. On the left, you have the visible light version of a shirt, on the right the IR version of the same shirt in the same scene and same everything.

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Introducing “Video Evidence Pitfalls: Because You Don’t Know What You Don’t Know”

Dear friends, I’m so glad to introduce this new blog series! Every Tuesday, for several weeks, we’ll walk together to discover some delicate or even dangerous aspects that you may easily encounter when dealing with images and videos during investigations. And of course, we’re not belittling your skills when we write “because you don’t know what you don’t know”! It’s just something that comes from our experience: we talk with investigators on a daily basis, and we’ve noticed that, sometimes, there’s a tendency to treat images and videos as “something everyone knows about”. All in all, we have them on our smartphones, we share them on social media, perhaps we also edit them with some consumer app or software from time to time, and with nice results.

Alas, my friends, it’s not that simple, for many reasons:

  1. Videos you deal with in forensics often come from CCTV surveillance systems. The acquisition and processing lifecycle of such videos is very different than what goes on in a smartphone. Smartphones have never dealt with analog video, while many CCTV systems still work with analog cameras connected to a DVR. And what about compression? One minute of video on my Google Pixel 3a is worth hundreds of megabytes, while it would probably be <10 MBs in a CCTV system.
  2. Video encoding and playback is a complex topic, and this is especially true when it comes to proprietary video formats, that are used by most surveillance systems. Those working in the field know that most of the time, the original video extracted from a DVR just won’t play in standard computer players, it is normal. How do we “convert” it to a playable video? There’s a whole world inside, and investigators must at least know that such a world… exists!
  3. Remember that a shallow interpretation could steer a whole investigation in the wrong direction. Want an example? Take a look at this infrared picture of a shirt.
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A Farewell to Tip Tuesday and a Collection of All 2020 Tips

Dear friends, it is with a bittersweet feeling that I’m announcing this will be the last Tip Tuesday. The bitter part is just because I’m a bit emotional and I got used to this weekly appointment… but the sweet part is that we’ll continue writing new posts in 2021, just a bit different… so the best is yet to come!

To say goodbye, I’ve prepared a list of the 52 tips that accompanied this difficult 2020, so you have them all here for quick reference. And if you want, you can also take a look at the list of 2019 tips.

Thanks to all our loyal followers, we’ll meet again next year (#bringon2021) ready for a new experience!

  1. Tired of Clicking? Learn How to Use Amped Authenticate’s Command Line Interface to Quickly Analyze or Triage Lots of Images!
  2. A Good Way to Say No: Show What’s Actually There With Amped Replay
  3. To Us “Nice” is Not Enough: Learn How to Further Improve Your Super-Resolution Images in Amped FIVE
  4. What Have I Done? Learn How to Effectively Show the Improvement You Achieved With Amped Replay
  5. Different Points of View? No Problem! Use Amped FIVE’s Perspective Aligner to Compare or Integrate Images Taken From Different Angles!
  6. Where Are You From? Learn How to Investigate Which Camera Model Took an Image Using Exif Metadata and JPEG Quantization Tables
  7. Lights, Camera, Action! Amped Replay Now Lets You Easily Handle Multiple Annotations
  8. Brilliant Details: Learn How to Use Amped FIVE’s Macros to Add Adaptive Text to Your Frames and Make Compelling Videos
  9. The Truth Will Come Out: Easily Verify Time and Location Metadata With Amped Authenticate and Avoid Being Deceived by Them!
  10. To Rotate or Not To Rotate? Learn How Amped Replay’s Rotate Filter Works and When You Should Use It
  11. Let’s Get Loud! The Latest Amped FIVE Supports Audio More Than Ever, Take a Quick Tour Into This New World!
  12. The Sound of Silence: Learn How to Redact Audio in Amped FIVE
  13. When Sound Beats Light: Use Amped FIVE to Synch Videos Leveraging Their Audio Tracks!
  14. Unity Is Strength! In Challenging Cases, Amped Authenticate’s Compare CRP Makes Source Device Identification More Accurate
  15. Few GBs Left? Slow Connection? Amped Replay Lets You Pick Just the Frames You Need, so You Save Data and Don’t Lose Quality!
  16. Go Live! Let Your PC Be a Witness Using Amped FIVE’s Video Input to Record Everything You Do
  17. Using Amped Authenticate for Video Source Identification When You Only Have Images As Reference
  18. Pick the Best Frames With Amped Replay’s Bookmarks to Save Time and Focus on What Matters Most
  19. How Tall Is the Bad Guy? Reverse Projection in Amped Five With the Video Input Filter
  20. Amped Authenticate’s PRNU Tampering Filter Turns Sensor Noise Into an Effective Forgery Localization Tool!
  21. Speed Matters! Amped Replay’s Smooth Playback Makes Playback Fluid Even for High-Resolution Videos
  22. Did You Know Amped FIVE Allows Real-Time Processing on a Live Video?
  23. Discover Adaptive JPEG Quantization Tables and Save Yourself From Headaches!
  24. What Is “Better”? Understanding the Differences Between Amped FIVE or Amped Replay vs Consumer Video Players
  25. Trading Time for Definition: Learn How to Master Amped FIVE’s Frame Averaging Filter
  26. Yes, It Makes the Difference! A Practical Guide to Why You Should Keep Your Amped Products Up To Date
  27. Trading Time for Definition Part 2: Temporal and Motion Smoothing Are the Way to Cleaner and Ghost-Free Videos!
  28. Deeper and Deeper: Learn How to Verify the Consistency of Image Sequences With Some Less-Known Metadata!
  29. File Management, Exporting and Backup in Amped Replay
  30. Stay in the Range! Learn How to Use Amped FIVE’s Show Saturation Feature to Spot Saturated Pixels in Your Images
  31. Learn How to Use Amped Authenticate’s Shadows Filter Like a Pro for Clearer Results and Faster Processing!
  32. Customizable Power! Learn How to Customize Amped Replay Interface and Show Only the Features That You Need
  33. What’s in Your Past? A Guide to Spotting Traces of Double JPEG Compression With Amped Authenticate (Part 1)
  34. Are You Using the Best Possible Evidence? Amped FIVE’s Video Mixer Helps You Compare Frames and Answer the Question!
  35. What’s in Your Past? A Guide to Spotting Traces of Double JPEG Compression With Amped Authenticate (Part 2)
  36. A Guide to Video Exporting Options In Amped Replay
  37. Amped FIVE’s Histogram Tool: A Simple And Effective Way to Guide Your Enhancement!
  38. How to Use Amped Authenticate to Reveal Traces of Former JPEG Compression in Seemingly Uncompressed Images
  39. Handle With Care: Edit Project Files With a Text Editor
  40. Make Impressive Annotations in Seconds with Amped Replay’s Assisted Tracking
  41. Learn How to Use Amped FIVE’s Video Mixer to Compare Different Points of the Same Chain
  42. A Guide to Various Ways of Exporting Results in Amped Authenticate
  43. Layered Perfection: Learn Different Ways of Adding Multiple Annotations With Amped FIVE
  44. Learn How to Lock Annotations and Prevent Accidental Modifications in Amped Replay and Amped FIVE
  45. How to Quickly Find Manipulated Objects With Amped Authenticate’s Shadows Filter
  46. A Short Guide to Choosing the Right Export Format For Your Images and Videos: Part 1
  47. A Short Guide to Choosing the Right Export Format For Your Images and Videos: Part 2
  48. Change Frame Rate and Convert Frame Rate: Which One Should You Use in Your Case
  49. Discover the Power of the Amped FIVE Assistant With a Guided Example
  50. Learn How to Create Your Own Amped FIVE Assistant Scripts, It’s a Game Changer!
  51. How to Use Amped Authenticate Video PRNU to Check Whether a Video and Some Images Are From the Same Camera
  52. This one!

See you in 2021!

How to Use Amped Authenticate Video PRNU to Check Whether a Video and Some Images Are From the Same Camera

Dear friends welcome to this waiting-for-Santa tip! Less than a week has passed since the latest Amped Authenticate update (if you’ve missed it, take a look here!), and we’re already providing a tip to make the most of the new Video PRNU tool! In particular, today we’ll deal with a case where we need to check whether a video comes from a device, but we only have reference images of it. We’ll see that, with the latest Authenticate update, this is very easy to do!

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Discover the Power of the Amped FIVE Assistant With a Guided Example

Dear Amped friends, welcome! Today we’re sharing a tip that’s been waiting for too long: it’s about Amped FIVE‘s Assistant! It’s a very powerful and handy tool, but many users tend to forget about it… just because they’ve never tried it! We’re thus dedicating a mini-series to the Assistant. Take a breath and dive with us!

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