Changeset 29893 for main/trunk/model-sites-dev/respooled/collect/popup-video-respooled/js/key-detection.js

Timestamp:

2015-05-18T16:42:17+12:00 (9 years ago)

Author:

davidb

Message:

Completed version of Krumhansl's algorithm. Plus adding in of About bar. Plus tidy up of the 'by xxx' template

File:

• main/trunk/model-sites-dev/respooled/collect/popup-video-respooled/js/key-detection.js (modified) (3 diffs)

main/trunk/model-sites-dev/respooled/collect/popup-video-respooled/js/key-detection.js

@@ -1 +1 @@
 "use strict";
 
-// From:
+// Key detection algorithm, as described at:
 //  http://rnhart.net/articles/key-finding/
+
+// (from this web site) ....
+//  Krumhansl-Schmuckler key-finding algorithm (by Carol L. Krumhansl
+//  and Mark A. Schmuckler). The profile numbers came from experiments
+//  done by Krumhansl and Edward J. Kessler. The experiments consisted
+//  of playing a set of context tones or chords, playing a probe tone,
+//  and asking a listener to rate how well the probe tone fit with the
+//  context. You can read about the experiments and the algorithm in
+//  Krumhansl's book Cognitive Foundations of Musical Pitch. (The
+//  experiments are described in Chapter 2. The key-finding algorithm
+//  is described in Chapter 4.) You may be able to read portions of
+//  the book on Google Books.
+
+
+function khMean(vals) 
+{
+    var len = vals.length;
+    if (len==0) {
+    return 0;
+    }
+
+    var total = 0;
+
+    for (var i=0; i<len; i++) {
+    total += vals[i];
+    }
+
+    return total/len;
+}
+
+function khUnbiased(vals) 
+{
+    var unbiased_vals = [];
+
+    var len = vals.length;
+    if (len==0) {
+    return unbiased_vals;
+    }
+
+    var avg = khMean(vals);
+
+    for (var i=0; i<len; i++) {
+    unbiased_vals.push(vals[i] - avg)
+    }
+
+    return unbiased_vals;
+}
+
+
+function khCorrelationCoefficientUnbiased(a1,a2)
+{
+    var a1_len = a1.length;
+    var a2_len = a2.length;
+   
+    if (a1_len != a2_len) {
+    throw "khCorrelationCoefficientUnbiased(): arrays should be of the same length (" + a1_len + " vs " + a2_len + ")";
+    }
+    var len = a1_len;
+
+    var a1_a2_pair_prod = 0;
+    var a1_square = 0;
+    var a2_square = 0;
+
+    for (var i=0; i<len; i++) {
+    a1_a2_pair_prod += (a1[i]*a2[i]);
+    a1_square += (a1[i]*a1[i]);
+    a2_square += (a2[i]*a2[i]); 
+    }
+
+    return a1_a2_pair_prod / Math.sqrt(a1_square * a2_square);
+}
+
 
 //major profile
@@ -19 +91 @@
 var kh_minor_profile = [6.33, 2.68, 3.52, 5.38, 2.60, 3.53, 2.54, 4.75, 3.98, 2.69, 3.34, 3.17 ];
 
+var kh_major_profile_unbiased = khUnbiased(kh_major_profile);
+
+var kh_minor_profile_unbiased = khUnbiased(kh_minor_profile);
+
 
 function khCreatePairing(profile,chromatic_scale_durations,offset)
 {
-    var pairing = [];
-    for (var p=0; p<12; p++) {
-    pairing.push({"p":profile[p],"c":chromatic_scale_durations[(p+s)%12]});
+    var p = [];
+    var c = [];
+    for (var i=0; i<12; i++) {
+    p.push(profile[i])
+    c.push(chromatic_scale_durations[(i+offset)%12]);
     }
     
 
-    return pairing;
-}
-
-
-function khCreateAllPairings(chromatic_scale_durations,major_profile,minor_profile)
+    return {"p":p, "c":c};
+}
+
+
+function khCreateAllPairings(chromatic_scale_durations_unbiased,major_profile_unbiased,minor_profile_unbiased)
 {
     // chromatic_scale_durations.length = 12
@@ -45 +123 @@
     var scale = chromatic_keys[s];
 
-    major_pairings[scale] = khCreatePairing(major_profile,chromatic_scale_durations,s);
-    minor_pairings[scale] = khCreatePairing(minor_profile,chromatic_scale_durations,s);
+    major_pairings[scale] = khCreatePairing(major_profile_unbiased,chromatic_scale_durations_unbiased,s);
+    minor_pairings[scale] = khCreatePairing(minor_profile_unbiased,chromatic_scale_durations_unbiased,s);
     }
 
     return {"major" : major_pairings, "minor" : minor_pairings};
-
-}
-
-
+}
+
+function khComputeKeyCorrelationCoefficients(key_pairings_unbiased)
+{
+    var correlations = {};
+
+    var keys = Object.keys(key_pairings_unbiased);
+    var keys_len = keys.length;
+
+    for (var k=0; k<keys_len; k++) {
+    
+    var key = keys[k];
+    var key_pairing_unbiased = key_pairings_unbiased[key];
+
+    var correlation_coeff = khCorrelationCoefficientUnbiased(key_pairing_unbiased.p,key_pairing_unbiased.c);
+    correlations[key] = correlation_coeff;
+    }
+
+    return correlations;
+}
+
+
+function khComputeAllCorrelationCoefficients(pairings_unbiased)
+{
+    var major_correlation = khComputeKeyCorrelationCoefficients(pairings_unbiased.major);
+    var minor_correlation = khComputeKeyCorrelationCoefficients(pairings_unbiased.minor);
+
+    return {"major" : major_correlation, "minor" : minor_correlation};
+}
+
+function khFindMaxCorrelation(alignments)
+{
+    var max_val = 0;
+    var max_key = null;
+
+    var major_minor = [ "major", "minor" ];
+
+    for (var m=0; m<major_minor.length; m++) {
+    var mm = major_minor[m];
+    var mm_alignment = alignments[mm];
+
+    var mm_keys = Object.keys(mm_alignment);
+
+    for (var k=0; k<mm_keys.length; k++) {
+        var key = mm_keys[k];
+        var correlation_coeff = mm_alignment[key];
+        if (correlation_coeff>max_val) {
+        max_val = correlation_coeff;
+        max_key = key + " (" + mm + ")";
+        }
+    }
+    }    
+    
+    return { "key": max_key, "score": max_val };
+}
+
+function khKeyDetection(chromatic_scale_durations)
+{
+    // Work out durations of MIDI events folded into octave (60=Middle-C)
+    // (unbiased data)
+
+    //var chromatic_scale_durations = [ 432, 231, 0, 405, 12, 316, 4, 126, 612, 0, 191, 1];
+    var chromatic_scale_durations_unbiased = khUnbiased(chromatic_scale_durations);
+
+    // Generate all (unbiased) pairings
+    var kh_pairings_unbiased = khCreateAllPairings(chromatic_scale_durations_unbiased,kh_major_profile_unbiased,kh_minor_profile_unbiased)
+
+    // Compute Correlation Coefficients
+    var kh_alignments = khComputeAllCorrelationCoefficients(kh_pairings_unbiased);
+
+    // Pick highest values
+    
+    var strongest_profile = khFindMaxCorrelation(kh_alignments);
+
+    console.log("Predicted Key: " + JSON.stringify(strongest_profile));
+
+    return strongest_profile;
+
+}
+
+