2010:Audio Onset Detection

Description

Audio Onset Detection concerns itself with finding the time-locations of all sonic events in a piece of audio. This task was originally proposed in 2005 by Paul Brossier and Pierre Leveau . It has subsequently been run in 2005, 2006, 2007, 2009.

Data

Collections

The dataset will be the same as in 2005/2006/2007/2009 unless new or updated datasets are made available. The current dataset is subdivided into classes, because onset detection is sometimes performed in applications dedicated to a single type of signal (ex: segmentation of a single track in a mix, drum transcription, complex mixes databases segmentation...). The performance of each algorithm will be assessed on the whole dataset but also on each class separately.

The dataset contains 85 files from 5 classes annotated as follows:

• 30 solo drum excerpts cross-annotated by 3 people
• 30 solo monophonic pitched instruments excerpts cross-annotated by 3 people
• 10 solo polyphonic pitched instruments excerpts cross-annotated by 3 people
• 15 complex mixes cross-annotated by 5 people

Moreover the monophonic pitched instruments class is divided into 6 sub-classes: brass (2 excerpts), winds (4), sustained strings (6), plucked strings (9), bars and bells (4), singing voice (5).

Audio Formats

The data are monophonic sound files, with the associated onset times and data about the annotation robustness.

• CD-quality (PCM, 16-bit, 44100 Hz)
• single channel (mono)
• file length between 2 and 36 seconds (total time: 14 minutes)

Submission Format

Submissions to this task will have to conform to a specified format detailed below.

Input Data

Participating algorithms will have to read audio in the following format:

• Sample rate: 22 KHz
• Sample size: 16 bit
• Number of channels: 1 (mono)
• Encoding: WAV

Output data

The onset detection algorithms will return onset times in an ASCII text file. The specification is immediately below.

Onset file Format

<onset time(in seconds)>\n

where \n denotes the end of line. The < and > characters are not included.

README file

A README file accompanying each submission should contain explicit instructions on how to to run the program. In particular, each command line to run should be specified, using %input% for the input sound file and %output% for the resulting text file.

For instance, to test the program foobar with different values for parameters param1 and param2, the README file would look like:

foobar -param1 .1 -param2 1 -i %input% -o %output%
foobar -param1 .1 -param2 2 -i %input% -o %output%
foobar -param1 .2 -param2 1 -i %input% -o %output%
foobar -param1 .2 -param2 2 -i %input% -o %output%
foobar -param1 .3 -param2 1 -i %input% -o %output%
...

For a submission using MATLAB, the README file could look like:

matlab -r "foobar(.1,1,'%input%','%output%');quit;"
matlab -r "foobar(.1,2,'%input%','%output%');quit;"
matlab -r "foobar(.2,1,'%input%','%output%');quit;" 
matlab -r "foobar(.2,2,'%input%','%output%');quit;"
matlab -r "foobar(.3,1,'%input%','%output%');quit;"
...

The different command lines to evaluate the performance of each parameter set over the whole database will be generated automatically from each line in the README file containing both '%input%' and '%output%' strings.

Evaluation procedures

The detected onset times will be compared with the ground-truth ones. For a given ground-truth onset time, if there is a detection in a tolerance time-window around it, it is considered as a correct detection (CD). If not, there is a false negative (FN). The detections outside all the tolerance windows are counted as false positives (FP). Doubled onsets (two detections for one ground-truth onset) and merged onsets (one detection for two ground-truth onsets) will be taken into account in the evaluation. Doubled onsets are a subset of the FP onsets, and merged onsets a subset of FN onsets.

We define:

Precision

   P = Ocd / (Ocd +Ofp) 

Recall

   R = Ocd / (Ocd + Ofn) 

F-measure

   F = 2*P*R/(P+R) 

with these notations:

Ocd

   number of correctly detected onsets (CD) 

Ofn

   number of missed onsets (FN) 

Om

   number of merged onsets 

Ofp

   number of false positive onsets (FP) 

Od

   number of double onsets 

Other indicative measurements:

FP rate

   FP = 100. * (Ofp) / (Ocd+Ofp) 

Doubled Onset rate in FP

   D = 100 * Od / Ofp 

Merged Onset rate in FN

   M = 100 * Om / Ofn 

Because files are cross-annotated, the mean Precision and Recall rates are defined by averaging Precision and Recall rates computed for each annotation.

To establish a ranking, we will use the F-measure, widely used in string comparisons. This criterion is arbitrary, but gives an indication of performance. It must be remembered that onset detection is a preprocessing step, so the real cost of an error of each type (false positive or false negative) depends on the application following this task.

Evaluation measures:

• percentage of correct detections / false positives (can also be expressed as precision/recall)
• time precision (tolerance from +/- 50 ms to less). For certain file, we can't be much more accurate than 50 ms because of the weak annotation precision. This must be taken into account.
• separate scoring for different instrument types (percussive, strings, winds, etc)

More detailed data:

• percentage of doubled detections
• speed measurements of the algorithms
• scalability to large files
• robustness to noise, loudness