Add new filter method to generic filters

Issue #370 To filter on event duration during generic post-processing
QutEcoacoustics · Oct 14, 2020 · 2b41782 · 2b41782
1 parent 53e9c4d
commit 2b41782
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Showing 2 changed files with 61 additions and 6 deletions.
diff --git a/src/AnalysisPrograms/Recognizers/GenericRecognizer.cs b/src/AnalysisPrograms/Recognizers/GenericRecognizer.cs
@@ -334,13 +334,25 @@ public override RecognizerResults Recognize(
                 }
             }
 
-            // 3: Filter the events for bandwidth in Hertz
-            var expectedEventBandwidth = postprocessingConfig.Bandwidth.ExpectedBandwidth;
-            var sd = postprocessingConfig.Bandwidth.BandwidthStandardDeviation;
-            allResults.NewEvents = EventFilters.FilterOnBandwidth(allResults.NewEvents, expectedEventBandwidth, sd, sigmaThreshold: 3.0);
-            Log.Debug($"Event count after filtering on bandwidth = {allResults.NewEvents.Count}");
+            // 3: Filter the events for time duration (seconds)
+            if (postprocessingConfig.Duration != null)
+            {
+                var expectedEventDuration = postprocessingConfig.Duration.ExpectedDuration;
+                var sdEventDuration = postprocessingConfig.Duration.DurationStandardDeviation;
+                allResults.NewEvents = EventFilters.FilterOnDuration(allResults.NewEvents, expectedEventDuration, sdEventDuration, sigmaThreshold: 3.0);
+                Log.Debug($"Event count after filtering on duration = {allResults.NewEvents.Count}");
+            }
+
+            // 4: Filter the events for bandwidth in Hertz
+            if (postprocessingConfig.Bandwidth != null)
+            {
+                var expectedEventBandwidth = postprocessingConfig.Bandwidth.ExpectedBandwidth;
+                var sdBandwidth = postprocessingConfig.Bandwidth.BandwidthStandardDeviation;
+                allResults.NewEvents = EventFilters.FilterOnBandwidth(allResults.NewEvents, expectedEventBandwidth, sdBandwidth, sigmaThreshold: 3.0);
+                Log.Debug($"Event count after filtering on bandwidth = {allResults.NewEvents.Count}");
+            }
 
-            // 4: Filter events on the amount of acoustic activity in their upper and lower neighbourhoods - their buffer zone.
+            // 5: Filter events on the amount of acoustic activity in their upper and lower neighbourhoods - their buffer zone.
             //    The idea is that an unambiguous event should have some acoustic space above and below.
             //    The filter requires that the average acoustic activity in each frame and bin of the upper and lower buffer zones should not exceed the user specified decibel threshold.
             var sidebandActivity = postprocessingConfig.SidebandActivity;
@@ -452,12 +464,33 @@ public class PostProcessingConfig
             /// </summary>
             public SidebandConfig SidebandActivity { get; set; }
 
+            /// <summary>
+            /// Gets or sets the parameters required to filter events on their duration.
+            /// </summary>
+            public DurationConfig Duration { get; set; }
+
             /// <summary>
             /// Gets or sets the parameters required to filter events on their bandwidth.
             /// </summary>
             public BandwidthConfig Bandwidth { get; set; }
         }
 
+        /// <summary>
+        /// The next two properties determine filtering of events based on their duration.
+        /// </summary>
+        public class DurationConfig
+        {
+            /// <summary>
+            /// Gets or sets a value indicating the Expected duration of an event.
+            /// </summary>
+            public double ExpectedDuration { get; set; }
+
+            /// <summary>
+            /// Gets or sets a value indicating the standard deviation of the expected duration.
+            /// </summary>
+            public double DurationStandardDeviation { get; set; }
+        }
+
         /// <summary>
         /// The next two properties determine filtering of events based on their bandwidth.
         /// </summary>

diff --git a/src/AudioAnalysisTools/Events/EventFilters.cs b/src/AudioAnalysisTools/Events/EventFilters.cs
@@ -100,6 +100,28 @@ public static List<EventCommon> FilterOnDuration(List<EventCommon> events, doubl
             return outputEvents;
         }
 
+        /// <summary>
+        /// Filters lists of spectral events based on their duration.
+        /// Note: The typical sigma threshold would be 2 to 3 sds.
+        /// </summary>
+        /// <param name="events">The list of events.</param>
+        /// <param name="average">The expected value of the duration.</param>
+        /// <param name="sd">The standard deviation of the duration.</param>
+        /// <param name="sigmaThreshold">THe sigma value which determines the max and min thresholds.</param>
+        /// <returns>The filtered list of events.</returns>
+        public static List<EventCommon> FilterOnDuration(List<EventCommon> events, double average, double sd, double sigmaThreshold)
+        {
+            var minDuration = average - (sd * sigmaThreshold);
+            if (minDuration < 0.0)
+            {
+                throw new Exception("Invalid seconds duration passed to method EventExtentions.FilterOnDuration().");
+            }
+
+            var maxDuration = average + (sd * sigmaThreshold);
+            var outputEvents = events.Where(ev => ((SpectralEvent)ev).EventDurationSeconds > minDuration && ((SpectralEvent)ev).EventDurationSeconds < maxDuration).ToList();
+            return outputEvents;
+        }
+
         /// <summary>
         /// Removes composite events from a list of EventCommon that contain more than the specfied number of SpectralEvent components.
         /// </summary>