August 2005

From the Lab: Information Technology

Continued from page 2

By Technology Review

Sampling Songs
Digital fingerprints make for easier searching

Results: Microsoft researchers have developed software that can automatically identify audio files--including streaming audio--by extracting and encoding short sections of them to form "fingerprints." Christopher Burges and colleagues have developed two new applications for this audio-recognition technology: identifying duplicate files in a large collection of audio files and creating "thumbnails," 15-second-long, recognizable snippets of each file. The software found duplicates in a database of more than 40,000 audio files with a 1.2 percent error rate. In another test involving 68 songs, a panel of users compared thumbnails made with the Microsoft software with snippets of the songs beginning 30 seconds in, and rated the Microsoft thumbnails more likely to contain the titles, choruses, or other distinctive features of the songs.

Why it Matters: Today's digital-audio libraries are growing in size, and users must manually sort through them to find and remove duplicate files. Microsoft's method of spotting duplicates could make for easier and faster consolidation of large song collections. Many online music purveyors also offer their customers previews of songs. Currently, those previews are created either manually--someone listens to the song to find a recognizable chorus, then makes the song snippet--or via software that samples only a predetermined segment of each song, which may not contain readily recognizable material. The new software can automatically find the defining part of a song when extracting a thumbnail, making the thumbnail a better indicator of the song's identity.

Methods: The duplicate detector extracts a fingerprint for each file and puts it into a database. To compare two songs, it considers the location from which the first song's fingerprint was extracted and looks for a matching fingerprint in the same vicinity in the second song. If it finds a match, it identifies the two as duplicates. After analyzing all the songs in the database, the detector presents the user with a list of duplicate songs.

The thumbnail generator compares fingerprints within a file. If it finds similar fingerprints at different points, it identifies them as the song's chorus or some other characteristic feature. If fingerprint analysis doesn't find a clear repeating feature, the software can analyze other aspects of the song, such as patterns of sound frequencies, to pick out a characteristic section. The software then extracts the 15 seconds of audio surrounding that section as the thumbnail.

Next Step: The researchers are working with Microsoft's product teams to commercialize this technology. Potential applications might include software that cleans up music collections on home computers, freeing up disk space. Online music vendors could also use the thumbnail generator to create previews of the songs offered on their websites. -- By Jean Thilmany

Source: Burges, C., et al. 2005. Using audio fingerprinting for duplicate detection and thumbnail generation. Paper presented at the IEEE Conference on Acoustics, Speech, and Signal Processing. March 18-23. Philadelphia, PA.