Colored blocks 3 across, 5 deep appearing on an edited video

We have a case before us where the police department doctored a video to redact various scenes where the police attacked an individual. Their editing of the video left a series of colored blocks on each frame of the video. The State Attorney had a copy of that video, as did the Public Defender who represented the Defendant until the time of trial. Each have now represented that they have lost their copy of that CD-ROM, and they now seek to prevent the defendant from showing the court the redacted video. What significance do these consistent and stationary colored blocks have? Is there a system that will add these blocks to to the extruded CD-ROM? Any other information that can be offered will be appreciated. The Defendant has already done 4 years in prison based upon this altered evidence.

The colored blocks can be from bad DVD compression. As you may know all dvd technology uses MPEG compression. If the source video was grainy or snowy and the compressor used is of a bad quality, that is to say not a broadcast quality, the output DVD may contain MPEG compression artifacts. I would have to see the video or a screen capture for myself to know for sure.

On the other hand if the blocks are nearly the same size and color every time I would be inclined to believe that they are intentional and put there on purpose to cover up land marks/logos/faces or other identifying information.

If you would need any further help feel free to mail me at skinwill att gmail

I sent a response to your email under separate cover. This altered CD was on CD-ROM.

I don't know how they got there, what they are for, and no one else seems to know, either. They do know that the video was altered, but the colored dots have everyone stumped.

Thanks,

John McNamara

Without actually seeing the video in question I can only make an educated guess as to what the blocks are. My guess is that video was altered using a either an effects software plug-in in a non-linear video editing system or with a Digital Video Effects (DVE) device in a linear edit suite. It's a fairly common way to mask faces, license plates, nudity, etc. for television. If it is this effect then the "pixelated" blocks that you're seeing will most likely change color and luminance slightly as the camera moves or as elements within the video through and under the blocks. The effect is commonly known as mosaic blurring. This method was used widely years ago when inexpensive software and hardware would have been unable to do fine blurring. It is largely unused today in favor of simple blurring; however the effect is still available as a creative tool. The unfortunate part of this for you is that the effect is unreversable since the information that used to be in the area where the blocks are is lost. The only way to get back the missing visual elements would be to go to the original source tape(s) used to create the altered video.