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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.