Improve unintelligibility algorithm (#141)

* Improve unintelligibility algorithm Make signal to noise ratio configurable Signed-off-by: Dave Thaler <[email protected]> * Remove obsolete configuration parameter ORCASOUND_MIN_INTELLIGIBLE_STREAM_DEVIATION No longer used in the new unintelligibility algorithm. Signed-off-by: Dave Thaler <[email protected]> * Add test case file Signed-off-by: Dave Thaler <[email protected]> --------- Signed-off-by: Dave Thaler <[email protected]>
orcasound · Oct 1, 2024 · bcd27d6 · bcd27d6
1 parent 89eceb2
commit bcd27d6
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Showing 5 changed files with 15 additions and 32 deletions.
diff --git a/OrcanodeMonitor/Core/FfmpegCoreAnalyzer.cs b/OrcanodeMonitor/Core/FfmpegCoreAnalyzer.cs
@@ -16,9 +16,17 @@ public class FfmpegCoreAnalyzer
 
         // Minimum ratio of amplitude outside the hum range to amplitude
         // within the hum range.  So far the max in a known-unintelligible
-        // sample is 10% and the min in a known-good sample is 50%.  So for
-        // now we use 20%.
-        const double MinSignalRatio = 0.20;
+        // sample is 21% and the min in a known-good sample is 50%.
+        const double _defaultMinSignalPercent = 30;
+        private static double MinSignalRatio
+        {
+            get
+            {
+                string? minSignalPercentString = Environment.GetEnvironmentVariable("ORCASOUND_MIN_INTELLIGIBLE_SIGNAL_PERCENT");
+                double minSignalPercent = double.TryParse(minSignalPercentString, out var percent) ? percent : _defaultMinSignalPercent;
+                return minSignalPercent / 100.0;
+            }
+        }
 
         // Microphone audio hum typically falls within the 50 Hz to 60 Hz
         // range. This hum is often caused by electrical interference from

diff --git a/OrcanodeMonitor/Models/Orcanode.cs b/OrcanodeMonitor/Models/Orcanode.cs
@@ -216,16 +216,6 @@ private static TimeSpan MaxUploadDelay
             }
         }
 
-        private static double MinIntelligibleStreamDeviation
-        {
-            get
-            {
-                string? minIntelligibleStreamDeviationString = Environment.GetEnvironmentVariable("ORCASOUND_MIN_INTELLIGIBLE_STREAM_DEVIATION");
-                double minIntelligibleStreamDeviation = double.TryParse(minIntelligibleStreamDeviationString, out var deviation) ? deviation : _defaultMinIntelligibleStreamDeviation;
-                return minIntelligibleStreamDeviation;
-            }
-        }
-
         /// <summary>
         /// Value in the latest.txt file, as a Local DateTime.
         /// </summary>
@@ -303,8 +293,7 @@ public OrcanodeOnlineStatus S3StreamStatus
 
                 if (AudioStreamStatus == OrcanodeOnlineStatus.Absent && AudioStandardDeviation != 0.0)
                 {
-                    // Fall back to legacy algorithm.
-                    AudioStreamStatus = (IsUnintelligible(AudioStandardDeviation)) ? OrcanodeOnlineStatus.Unintelligible : OrcanodeOnlineStatus.Online;
+                    AudioStreamStatus = OrcanodeOnlineStatus.Online;
                 }
 
                 return AudioStreamStatus ?? OrcanodeOnlineStatus.Absent;
@@ -325,21 +314,6 @@ public string OrcasoundOnlineStatusString {
 
         #region methods
 
-        /// <summary>
-        /// Function used for backwards compatibility when reading a database
-        /// entry with no AudioStreamStatus.
-        /// </summary>
-        /// <param name="audioStandardDeviation"></param>
-        /// <returns></returns>
-        public static bool IsUnintelligible(double? audioStandardDeviation)
-        {
-            if (audioStandardDeviation.HasValue && (audioStandardDeviation < MinIntelligibleStreamDeviation))
-            {
-                return true;
-            }
-            return false;
-        }
-
         public OrcanodeIftttDTO ToIftttDTO() => new OrcanodeIftttDTO(ID, DisplayName);
 
         /// <summary>

diff --git a/Test/UnintelligibilityTests.cs b/Test/UnintelligibilityTests.cs
@@ -24,7 +24,7 @@ private async Task TestSampleAsync(string filename, OrcanodeOnlineStatus expecte
             try
             {
                 OrcanodeOnlineStatus status = await FfmpegCoreAnalyzer.AnalyzeFileAsync(filePath);
-                Assert.IsTrue(status ==  expected_status);
+                Assert.IsTrue(status == expected_status);
             }
             catch (Exception ex)
             {
@@ -38,6 +38,7 @@ private async Task TestSampleAsync(string filename, OrcanodeOnlineStatus expecte
         [TestMethod]
         public async Task TestUnintelligibleSample()
         {
+            await TestSampleAsync("unintelligible\\live4869.ts", OrcanodeOnlineStatus.Unintelligible);
             await TestSampleAsync("unintelligible\\live1816b.ts", OrcanodeOnlineStatus.Unintelligible);
             await TestSampleAsync("unintelligible\\live1791.ts", OrcanodeOnlineStatus.Unintelligible);
             await TestSampleAsync("unintelligible\\live1815.ts", OrcanodeOnlineStatus.Unintelligible);

diff --git a/Test/samples/unintelligible/live4869.ts b/Test/samples/unintelligible/live4869.ts
diff --git a/docs/Design.md b/docs/Design.md
@@ -100,7 +100,7 @@ The following state will be stored per orcanode:
 
 **ORCASOUND_MAX_UPLOAD_DELAY_MINUTES**: If the manifest file is older than this, the node will be considered offline. Default: 2
 
-**ORCASOUND_MIN_INTELLIGIBLE_STREAM_DEVIATION**: The minimum standard deviation needed to determine that an audio stream is intelligible. Default: 175
+**ORCASOUND_MIN_INTELLIGIBLE_SIGNAL_PERCENT**: The minimum percentage of max amplitude across all frequencies of amplitude outside the 50-60 Hz range needed to determine that an audio stream is intelligible. Default: 30
 
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