From 910e85a90a5c66b0864338e5996bfaaf2013dd3d Mon Sep 17 00:00:00 2001
From: Ichthyostega <prg@ichthyostega.de>
Date: Sun, 31 Aug 2014 01:57:05 +0200
Subject: [PATCH] =?UTF-8?q?Erkennung=20von=20Signal-Spr=C3=BCngen=20implem?=
 =?UTF-8?q?entiert?=
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---
 sauSynKlick/SynKlick.cc | 61 +++++++++++++++++++++++++++++++++--------
 1 file changed, 50 insertions(+), 11 deletions(-)

diff --git a/sauSynKlick/SynKlick.cc b/sauSynKlick/SynKlick.cc
index 6348ae5..260ceb4 100644
--- a/sauSynKlick/SynKlick.cc
+++ b/sauSynKlick/SynKlick.cc
@@ -1,5 +1,5 @@
 /*
- SynKlick  -  repair synchronous drop-outs in raw sound recording
+ SynKlick  -  repair synchronous skips in raw sound recording
 
  (C) Ichthyostega (Hermann Vosseler), 2014
 
@@ -14,19 +14,25 @@ GNU PUBLIC LICENCE (GPL) Version 2 and above.
 
 #include <string>
 #include <vector>
+#include <iostream>
 #include <cassert>
 #include <cstdlib>
-#include <iostream>
+#include <cmath>
 
 using std::string;
 using std::vector;
 using std::cout;
 using std::cerr;
+using std::abs;
 
-const size_t BUFF_SIZE  = 20000; //44100;  ///TODO for debugging
+const size_t CHUNK_SIZE  = 20000; //44100;  ///TODO for debugging
 const size_t CONTEXT    = 100;
-const size_t CHUNK_SIZE = BUFF_SIZE + 2*CONTEXT;
+const size_t BUFF_SIZE = CHUNK_SIZE + 2*CONTEXT;
 
+const float EPSILON = 1.0f / (1 << 23);      // one normalised sample step for 24bit samples 
+const float SILENCE_GATE = 1024.0f * EPSILON;// signal below this level (-39dB) is too low to detect jumps
+const float TRIGGER_FACTOR = 6.0f;           // discontinuity detected by local change compared to average change
+const uint  AVERAGE_SAMPLES = 50;            // number of past samples to use for average delta
 
 /* ==== Helpers ==== */
 
@@ -74,9 +80,10 @@ class Channel
     SF_INFO info_in_,
             info_out_;
     
-    float buff_[CHUNK_SIZE];
+    float buff_[BUFF_SIZE];
     size_t numSamples_ = 0;
     size_t workPos_    = 0;
+    float ema_ = 1.0f / TRIGGER_FACTOR;
     
     
   public:
@@ -120,9 +127,9 @@ class Channel
     void
     fillBuffer()
       {
-        assert(numSamples_ < CHUNK_SIZE);
+        assert(numSamples_ < BUFF_SIZE);
         float* startPos = buff_ + numSamples_;
-        size_t samplesToRead = CHUNK_SIZE - numSamples_;
+        size_t samplesToRead = BUFF_SIZE - numSamples_;
         numSamples_ = sf_read_float(in_, startPos, samplesToRead);
         if (numSamples_ < samplesToRead)
           hitEnd = true; // causes the processing to end with this chunk.
@@ -170,10 +177,35 @@ class Channel
             && workPos_ <= i)
           {
             workPos_ = i;
+            float averageDelta = updateMovingAverage();
+            float changeFactor = delta() / (averageDelta + EPSILON);
+            if (event != NO && SILENCE_GATE < abs(sample()))
+              event = (changeFactor > TRIGGER_FACTOR? YES : NO);
           }
         return event;
       }
     
+  private:
+    float
+    sample()
+      {
+        return buff_[workPos_];
+      }
+    
+    float
+    delta()
+      {
+        if (0 < workPos_)
+          return abs(buff_[workPos_] - buff_[workPos_-1]);
+        else
+          return 0;
+      }
+    
+    float
+    updateMovingAverage()
+      {
+        return ema_ = (delta() + ema_*(AVERAGE_SAMPLES - 1)) / AVERAGE_SAMPLES;
+      }
   };
 
 
@@ -199,7 +231,7 @@ class Patch
     void
     apply()
       {
-        error("TODO");
+        cerr << "TODO\n";
       }
   };
 
@@ -239,21 +271,28 @@ closeStreams()
 void
 process()
 {
+  size_t absStartPos = 0; // for diagnostic messages
+  
   while (!Channel::hitEnd)
     {
       for (Channel& channel : streams)
         channel.fillBuffer();
-      for (uint i=0; i < CHUNK_SIZE; ++i)
+      for (uint i=0; i < BUFF_SIZE; ++i)
         {
           Event event = MAYBE;
           for (Channel& channel : streams)
             event = channel.visit(i, event);
           if (YES == event)
-            for (Channel& channel : streams)
-              Patch(channel).apply();
+            {
+              cout << "Skip-Event at "<< absStartPos+i <<"\n";
+              for (Channel& channel : streams)
+                Patch(channel).apply();
+            }
         }
       for (Channel& channel : streams)
         channel.writeBuffer();
+      
+      absStartPos += CHUNK_SIZE;
     }
 }