Audio Watermarking Technique Could Locate Movie Pirates

Movie Theater
By detecting the delay from different watermarked audio signals in a movie recording, a new technique can locate the recording position in a movie theater. Image credit: Fernando de Sousa.

( -- Camcorder piracy - which occurs when moviegoers bring a camcorder into a theater to record a movie from the screen - is a rapidly growing illegal activity. In the US, camcorder piracy has been illegal since 2005, when the Family Entertainment and Copyright Act banned the use of recording devices in theaters. Nevertheless, according to the Motion Picture Association, camcorder piracy causes an annual loss of $6.1 billion to the movie industry.

In an attempt to deter camcorder piracy, researchers have been developing watermarking techniques that embed a secret message into a movie indicating when and where the movie was shown. Once the movie is posted on the Internet, this secret message can be extracted to reveal the movie theater and showtime, and the theater can implement additional surveillance to deter piracy. However, these watermarking techniques cannot identify the recording location in the theater.

Now, a newly proposed position estimation system can use an audio watermarked signal embedded into a movie soundtrack to estimate the camcorder's location in a theater to within half a meter - basically down to a specific seat. Yuta Nakashima, Ryuki Tachibana, and Noboru Babaguchi of Osaka University have developed the new technique, and their results will be published in an upcoming issue of IEEE Transactions on Multimedia.

As the researchers explain in their study, the position estimation system works by taking advantage of the different channels of the soundtrack, called "host signals." A watermark embedder generates a watermark signal for each host signal, generating a "watermarked host signal" (WHS). Separate loudspeakers emit each WHS, and a camcorder will record the audio as a mixture of all the WHSs as a single recorded signal.

In this monaural recorded signal, the watermarked host signal from each loudspeaker is delayed in proportion to the distance from its loudspeaker (the source of origin) to the camcorder's microphone. The watermark detector can calculate these delays by determining the strengths of each watermarked host signal. Specifically, the detection strength of each watermarked signal will have a peak at a particular time dependent on the delay times.

As the researchers explain, this audio watermarking method could be combined with a conventional watermarking method, which together could determine the move theater, showtime, and the seat in the theater. Then, a person identification system - such as a ticketing system or video surveillance - could identify the pirate.

Although the researchers performed experiments with the system, they plan to investigate the technique further. One challenge they face is ensuring that the acoustic quality remains high in the midst of various environmental factors and background noise. The researchers also plan to investigate the robustness of the system against attacks that may cause the system to estimate an irrelevant position, and to detect these attacks and account for them, if necessary.

More information: Nakashima, Yuta; Tachibana, Ryuki; and Babaguchi, Noboru. "Watermarked Movie Soundtrack Finds the Position of the Camcorder in a Theater." IEEE Transactions on Multimedia. To be published.

© 2009

Citation: Audio Watermarking Technique Could Locate Movie Pirates (2009, February 26) retrieved 21 August 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Feb 26, 2009
lol, these clowns.

Who the hell watches CAMs anyway? Trust me, if you're desperate enough to watch a CAM you're probably NEVER going to pay for a movie ticket. The MPAA can take their made-up fictitious monopoly money values and f'off.

Not to mention, even if CAMs WERE important, obviously they could scrub out the watermark. So what the _ do they think they're going to accomplish!?

And lol at no-recording devices in theaters... The countdown to banning cellphones is on. How fast can the theaters kill themselves?!

Notice how all the movies are coming out in 3D now? That's called desperation.

What a bunch of tiny minds. Good riddance!

Feb 26, 2009
seriously. who the hell watches a camcorder version of a movie? no one. no one worth their salt

Feb 26, 2009
Cool tech, but utterly pointless for all the reasons mentioned above. A real shame to see good engineers working on such projects.

Feb 26, 2009
The idea that theaters will be video taping every patron is bad, bad,,,,

Count me out....

Feb 27, 2009
Audio Watermarking - a solution in search of an obsolete problem. Torrent aXXo for your needs.

Feb 27, 2009
Might as well bring in a law forcing everyone to pay %u20AC100,000 for a tulip bulb.

Feb 27, 2009
Well shoot. I work in computer vision. Seems to me the move projects on a mostly flat surface and so with some standard homographies on known textures or feature points in the video and known dimensions of the theater, one ought to be able to locate the camera location to the centimeter.

Feb 27, 2009
These kinds of projects are doomed to fail. Only one person is needed in the _world_ to record the movie and put copy on the net - it's like trying to kill every mosquito on the planet.

Feb 27, 2009
^ lol. You make a very good point GaryB.

Unfortunately, difficulties may arise because the people distributing the CAM generally make modifications to the aspect ratio, among other things. They also, usually, scrub the audio for static and try to reproduce the bass that is lost by the tiny camcorder microphone.

That is, if they're not using an audio line out provided BY the theater for the hearing impaired. I presume this line out would not accurately reproduce the lag that this useless audio watermark needs to function. :)

Wow. I'd love to meet the guys that figured out how to get payed to find this 'solution.'

Feb 27, 2009
Why not spend millions on fixing a problem that costs them nothing. Idiots! If I watch a cam, its to see if a storyline sucks b4 I waste 10bucks on it in the cinema. Anyone that buys or profits from cam jobs are morons! Cams are as useful as a shit quality preview from youtube imo...

Feb 27, 2009
What's really incredible is that someone out there with lots of money thought this was a good idea. Shows what kind of people they have working for them.

Mar 01, 2009
It seems like a lot of effort to put into making a lock for a stable door that only activates after a horse has bolted.

Mar 02, 2009
Lost 6.1 billion??? from cams?? Prove it! And further more, if even a tiny fraction of that figure was lost, all that shows is that most movies are garbage anyways so WGAF. Hey here's an idea: Let the recording undustry use cams and then try to sell the finished product back to consumers. I'm sure in approx 1000 years they will have proved themselves as not being the greedy 2 bit individuals they come off as. I watched a good movie last night with a friend for approx 25-30 dollars. To be perfectly honest unless you are trying to impress a; 1-child, 2-fob immigrant, or 3-your girlfriend, you ARE better off waiting for the torrent dvd/rip. I will not go back to a theater for a very very long time. In these economic times that is truly a luxury for the rich.
Or look at it this way, transfer what you pay for your internet connect into theatre tickets or even a netflix acct on a monthly basis and it becomes painfully clear that the internet will win out every time.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more