The Null Device

This looks really impressive. It seems that Celemony (the makers of pitch/time-correcting sound editor Melodyne) have cracked one of the hard problems of digital audio processing: how to extract and modify individual notes in recorded chords. The video demonstrates this technique being used to transpose and re-edit recorded guitar chords as if they were MIDI scores, or even to play chords on a MIDI keyboard and have them played out using a sample. Which looks amazing, though, alas, it won't be with us until autumn (in the northern hemisphere).

¶ audio celemony melodyne cs dsp music tech want [2 comments]

Another use for all those neatly tagged photos of tourist attractions on websites like Flickr: synthesising accurate 3D models from millions of photos, taken by amateurs from random angles:

To make the 3D digital model, the researchers first download photos of a landmark. For instance, they might download the roughly 60,000 pictures on Flickr that are tagged with the words "Statue of Liberty." The computer finds photos that it will be able to use in the reconstruction and discards pictures that are of low quality or have obstructions. Photo Tourism, a tool developed at the UW, then calculates where each person was standing when he or she took the photo. By comparing two photos of the same object that were taken from slightly different perspectives, the software applies principles of computer vision to figure out the distance to each point.

"We don't quite get the accuracy of a laser scanner, but we're in the ballpark," Seitz said. The recreations of Notre Dame show individual figures carved into the stone facade. A model of The Duomo in Pisa, Italy, a building about 160 feet tall, is accurate to within a few inches. The resolution of the 3D model mostly depends on the resolution of the original photos.

(via /.) ¶ cs flickr graphics machine vision tech [no comments]

Science News has an article about recent advances in computer music processing. There has been success in creating software which understands recorded music, to the point of being able to extract note information from a (polyphonic, multitimbral, acoustically imperfect) recording. This has been achieved not by programming in rules of musical theory but by using machine learning techniques, setting up a learning system and training it from examples to infer its own rules of music:

He started with a program that had no information about how music works. He then fed into his computer 92 recordings of piano music and their scores. Each recording and score had been broken into 100-millisecond bits so that the computer program could associate the sounds with the written notes. Within those selections, the computer would receive an A note, for example, in the varying contexts in which it occurred in the music. The software could then search out the statistical similarities among all the provided examples of A.

In the process, the system indirectly figured out rules of music. For example, it found that an A is often played simultaneously with an E but seldom with an A-sharp, even though the researchers themselves never programmed in that information. Ellis says that his program can take advantage of that subtle pattern and many others, including some that people may not be aware of.

Score-alignment programs could be used after a musician records a piece of music to do the kind of fine-tuning that's now performed painstakingly by recording studios, fixing such problems as notes that are slightly off pitch or come in late. "It'll be kind of like a spell-check for music," says Roger Dannenberg, a computer scientist at Carnegie Mellon University in Pittsburgh who is developing the technology.

Christopher Raphael begins the third movement of a Mozart oboe quartet. As his oboe sounds its second note, his three fellow musicians come in right on cue. Later, he slows down and embellishes with a trill, and the other players stay right with him. His accompanists don't complain or tire when he practices a passage over and over. And when he's done, he switches them off.

(via Boing Boing) ¶ ai computer music cs music tech [no comments]