Thursday, August 7, 2014

The Visual Microphone: Passive Recovery of Sound from Video

The Visual Microphone: Passive Recovery of Sound from Video

Extracting audio from visual information
Algorithm recovers speech from the vibrations of a potato-chip bag filmed through soundproof glass.

Watch how MIT researchers extract audio from the vibrations of a plant, potato-chip bag, and other objects.
Video courtesy of the researchers

Researchers at MIT, Microsoft, and Adobe have developed an algorithm that can reconstruct an audio signal by analyzing minute vibrations of objects depicted in video. In one set of experiments, they were able to recover intelligible speech from the vibrations of a potato-chip bag photographed from 15 feet away through soundproof glass.
In other experiments, they extracted useful audio signals from videos of aluminum foil, the surface of a glass of water, and even the leaves of a potted plant. The researchers will present their findings in a paper at this year’s Siggraph, the premier computer graphics conference.
“When sound hits an object, it causes the object to vibrate,” says Abe Davis, a graduate student in electrical engineering and computer science at MIT and first author on the new paper. “The motion of this vibration creates a very subtle visual signal that’s usually invisible to the naked eye. People didn’t realize that this information was there.”
Joining Davis on the Siggraph paper are Fr├ędo Durand and Bill Freeman, both MIT professors of computer science and engineering; Neal Wadhwa, a graduate student in Freeman’s group; Michael Rubinstein of Microsoft Research, who did his PhD with Freeman; and Gautham Mysore of Adobe Research.
Reconstructing audio from video requires that the frequency of the video samples — the number of frames of video captured per second — be higher than the frequency of the audio signal. In some of their experiments, the researchers used a high-speed camera that captured 2,000 to 6,000 frames per second. That’s much faster than the 60 frames per second possible with some smartphones, but well below the frame rates of the best commercial high-speed cameras, which can top 100,000 frames per second.

Top 5 Most Absurd Pretexts for War in Modern History | Brainwash Update

Top 5  Most Absurd Pretexts for War in Modern History | Brainwash 

Abby Martin remarks on the 50th Anniversary of the Gulf of Tonkin incident, going a few of the most absurd pretexted for war in modern history.
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Published on Aug 5, 2014

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