Friday, 25 March 2016

Licence Plate Recovery

The good people at have set a 'license plate challenge', saying:

(Note: Doug asked me to block out the actual number plate in this blog post)

Unprecedented... Hmmm... Spready from Amped solved this challenge easily so I thought, I'm sure Kinesense can do this too using our Video Clarification toolkit.

Sure enough, a couple of clicks and the license plate is recovered:

To recover the plate, I used a histogram edit filter (to crop out some of the added noise), temporal median filter to recombine frames, and rotate to correct the orientation. Then I clicked 'histogram equalization' to make it a bit clearer'. About 5 clicks from start to finish.

However, this is clearly not a 'real' license recovery video. By that I mean, the noise 'mode' is artificial and manually added to create the 'license plate challenge', and would never happen in a real video job faced by law enforcement. That said a more realistic video would be solved using the same clarification filters. 

I dug out this example from my archives. It is a read covert surveillance video, in low light with an older analog bullet-cam connected to a commonly used brand of covert surveillance recorder. The issue was caused by the analog camera's auto-gain going too high in low light, and thus adding a huge amount of noise. Running the 'temporal median filter' across the video recovered license plates of any vehicle parked for more than a few minutes in view, or in this screenshot, it recovers the logo on the skip/dumpster.

VideoCleaner set a neat challenge. Recovery under these conditions is not too difficult with the right tools, and its great to see issues like this discussed and highlighted by the community.