Why does Aurio fail to compare my audio tracks?

Question

I'm constructing a web site for an choir to automatically evaluate candidates before they are invited to an audition. I'm maintaining a database of audio snippets that the candidate should sing.

I'm trying to use Aurio code from here: https://github.com/protyposis/Aurio. But I cannot get it to properly compare audio tracks that are slower or in a different scale.

private int findMatchesWang(String file1, String file2)
{
    // Setup the sources
    var audioTrack1 = new AudioTrack(new FileInfo(file1));
    var audioTrack2 = new AudioTrack(new FileInfo(file2));

    var profile = Aurio.Matching.Wang2003.FingerprintGenerator.GetProfiles()[0];
    var store = new Aurio.Matching.Wang2003.FingerprintStore(profile);
    var gen = new Aurio.Matching.Wang2003.FingerprintGenerator(profile);

    int hashCount = 0;

    gen.SubFingerprintsGenerated += delegate (object sender, SubFingerprintsGeneratedEventArgs e)
    {
        store.Add(e);
        hashCount += e.SubFingerprints.Count;
    };
    gen.Generate(audioTrack1);
    gen.Generate(audioTrack2);

    var matches = store.FindAllMatches();

    return matches.Count;
}

When file1 is identical to file2, the function returns the expected value (4686 matches). I tried calling the function with:

• file2 is same song as file1, but played slower (see file "slow.wav").

• file2 is same song as file1, but played in a different scale (see file "different-scale.wav").

In both cases, the function returns 0. Please find the files here: https://drive.google.com/drive/folders/10vKdc6C3InWpVs0g877Yub3ddv267GSZ?usp=sharing

Can anybody explain what's wrong?

Answer 1

The algorithms implemented in Aurio are not designed to match content with different speed or pitch/scale. They can only handle very very small changes in those dimensions, e.g. as they happen due to drifted sampling clocks between playback and recording devices (i.e. measurable, but not noticeable by human listeners).

(I am the author of the Aurio library)