Ask Slashdot: How To Determine If a Video Has Been Faked? 237
BStorm writes "The Toronto Mayor Rob Ford has been making headlines around the world, for allegedly smoking crack. This story was first broken by gawker.com, which is now crowd-funding $200,000 to buy the video in question. What do you look for to determine if a video has been faked? Of course I am only interested in the technical details and not the tawdry details related to this case ;) I live in Toronto, so the video still frame posted on Gawker certainly does look like Rob Ford."
Depends on the format... (Score:4, Informative)
With jpeg(and I think at least some of the mpeg flavors), quantization matrices can be your friend.
Different hardware and software [impulseadventure.com] uses different matrices. This isn't a slam-dunk(if somebody just lightened the image a bit to bring out the detail, the quantization matrix would scream "Photoshop!", despite that being pretty innocuous); but it makes it rather harder for a clueless faker to simulate a 'right off the camcorder' "authentic" video if the last compression was almost certainly performed with editing software.
Depending on the details of the format, there are likely to be a variety of other things that are optional or implementation-specific(at least within certain ranges) that can be examined to try to source a given file. If implementation(or quality level/encode settings)-specific details vary between sections of the video, or between parts of individual frames, that's probably a bad sign.
If you have enough footage, and ideally access to the alleged source hardware, you can also attempt to characterize physical defects in the sensor. All digital image sensors, to one degree or another, exhibit imperfect linearity. Some pixels are 'hot', some are abnormally insensitive, this is especially visible on long exposures, or in very dark scenes, where the hot pixels tend to stand out. Onboard image processors have gotten increasingly good at squelching minor sensor noise, so this isn't easy; but a given CCD or CMOS sensor will have a noise pattern that is extremely difficult to replicate. It's just an open question whether you'll actually be able to see enough noise to identify it.
Re:The pixels! (Score:4, Informative)
Re:it's really really hard (Score:5, Informative)
This is the same guy who spent over a decade refusing to report his expenses as a City Councillor, kept his election spending secret until a municipal auditor forced him to reveal that he had spent far more than he was legally allowed to, and was impeached last year after taking bribes from companies that did business with the city. Rather than pay back $3150 (about one week's pay for him) when asked to and making the entire issue go away, he insisted on a lengthy court battle which cost the city and province over $100,000, demonstrated that he really didn't know what the words "Conflict of Interest" meant even when they did bite him in the butt (repeatedly), and was finally removed from office by the Ontario Superior Court. A second, taxpayer-funded appeal overturned that decision, allowing his royal Fordness to continue showing respect for taxpayers and cutting the waste out of government spending.
Doing things the hard way isn't just a habit for Rob Ford, it's a way of life. He has a history of not doing the right thing even after every possible alternative has been exhausted -- He just makes up new things to do wrong. When confronted with a middle-aged woman dressed as Xena who tried to interview him for the CBC, he had a choice between talking to her or saying "No comment" and walking away. Instead, he called 911 and demanded that the police arrest her because, after all, he pays their salaries. When the story went public he insisted that he had done nothing wrong and certainly hadn't requested special treatment. All he needed to do to prove this was to ask that the recording of his 911 call be released to the public and he would be completely in the clear and never have to worry about it again.
Know what? I still haven't heard that recording. And I'm not holding my breath on seeing any kind of drug test or medical report either.