diff --git a/SyllableDetector/SyllableDetector.swift b/SyllableDetector/SyllableDetector.swift
index 98faa7d..5b4a407 100644
--- a/SyllableDetector/SyllableDetector.swift
+++ b/SyllableDetector/SyllableDetector.swift
@@ -39,7 +39,7 @@ class SyllableDetector: NSObject, AVCaptureAudioDataOutputSampleBufferDelegate
         self.config = config
         
         // initialize the FFT
-        shortTimeFourierTransform = CircularShortTimeFourierTransform(windowLength: config.windowLength, withOverlap: config.fourierOverlap, fftSizeOf: config.fourierLength)
+        shortTimeFourierTransform = CircularShortTimeFourierTransform(windowLength: config.windowLength, withOverlap: config.windowOverlap, fftSizeOf: config.fourierLength)
         shortTimeFourierTransform.windowType = WindowType.Hamming
         
         // store frequency indices
diff --git a/SyllableDetector/SyllableDetectorConfig.swift b/SyllableDetector/SyllableDetectorConfig.swift
index fe41419..72f1f58 100644
--- a/SyllableDetector/SyllableDetectorConfig.swift
+++ b/SyllableDetector/SyllableDetectorConfig.swift
@@ -30,9 +30,9 @@ struct SyllableDetectorConfig
     }
     
     var samplingRate: Double // eqv: samplerate
-    var windowLength: Int
-    var fourierLength: Int // eqv: FFT_SIZE
-    var fourierOverlap: Int // eqv: NOVERLAP = FFT_SIZE - (floor(samplerate * FFT_TIME_SHIFT))
+    let fourierLength: Int // eqv: FFT_SIZE
+    let windowLength: Int
+    var windowOverlap: Int // eqv: NOVERLAP = FFT_SIZE - (floor(samplerate * FFT_TIME_SHIFT))
     
     let freqRange: (Double, Double) // eqv: freq_range
     let timeRange: Int // eqv: time_window_steps = double(floor(time_window / timestep))
@@ -46,28 +46,23 @@ struct SyllableDetectorConfig
     mutating func modifySamplingRate(newSamplingRate: Double) {
         // store old things
         let oldSamplingRate = samplingRate
-        let oldFourierLength = fourierLength
-        let oldFourierOverlap = fourierOverlap
+        let oldWindowOverlap = windowOverlap
         
         if oldSamplingRate == newSamplingRate { return }
         
+        // window offset (difference in time between two consecutive windows)
+        // calculated using old values, but should be constant even after the new values
+        let windowOffset = Double(windowLength - oldWindowOverlap) / oldSamplingRate
         
-        // get new approximate fourier length
-        let newApproximateFourierLength = newSamplingRate * Double(oldFourierLength) / oldSamplingRate
-        
-        // convert to closest power of 2
-        let newFourierLength = 1 << Int(round(log2(newApproximateFourierLength)))
-        
-        // get new fourier overlap
-        let newFourierOverlap = newFourierLength - Int(round(newSamplingRate * Double(oldFourierLength - oldFourierOverlap) / oldSamplingRate))
+        let newWindowOverlap = windowLength - Int(round(windowOffset * newSamplingRate))
         
         // change the to new things
         samplingRate = newSamplingRate
-        fourierLength = newFourierLength
-        fourierOverlap = newFourierOverlap
+        windowOverlap = newWindowOverlap
         
-        DLog("New fourier length: \(newFourierLength)")
-        DLog("New fourier overlap: \(newFourierOverlap)")
+        DLog("Window offset: \(windowOffset)")
+        DLog("Sanity check: \(Double(windowLength - oldWindowOverlap) / oldSamplingRate)")
+        DLog("Window overlap: OLD \(oldWindowOverlap) NEW \(newWindowOverlap)")
     }
 }
 
@@ -234,7 +229,7 @@ extension SyllableDetectorConfig
         }
         
         // fourier length: int
-        fourierOverlap = try SyllableDetectorConfig.parseInt("fourierOverlap", from: data)
+        windowOverlap = try SyllableDetectorConfig.parseInt("windowOverlap", from: data)
         
         // frequency range: double, double
         let potentialFreqRange = try SyllableDetectorConfig.parseDoubleArray("freqRange", withCount: 2, from: data)
diff --git a/SyllableDetector/ViewControllerSimulator.swift b/SyllableDetector/ViewControllerSimulator.swift
index 3d5b040..4260372 100644
--- a/SyllableDetector/ViewControllerSimulator.swift
+++ b/SyllableDetector/ViewControllerSimulator.swift
@@ -242,7 +242,10 @@ class ViewControllerSimulator: NSViewController {
         assert(status == noErr)
         
         // processing
-        var nextCount: Int = sd.config.fourierLength + ((sd.config.fourierLength - sd.config.fourierOverlap) * (sd.config.timeRange - 1)), nextValue: Float = 0.0
+        var nextCount: Int = sd.config.windowLength + ((sd.config.windowLength - sd.config.windowOverlap) * (sd.config.timeRange - 1)), nextValue: Float = 0.0
+        if sd.config.windowOverlap < 0 {
+            nextCount = nextCount - sd.config.windowOverlap // since gap is applied even to the first data set
+        }
         var samplePosition: Int64 = 0
         let gcdGroup = dispatch_group_create()
         let gcdQueue = dispatch_queue_create("Encode", DISPATCH_QUEUE_SERIAL)
@@ -296,7 +299,7 @@ class ViewControllerSimulator: NSViewController {
                     }
                     
                     // length
-                    var l = sd.config.fourierLength - sd.config.fourierOverlap
+                    var l = sd.config.windowLength - sd.config.windowOverlap
                     
                     for ; 0 < l && i < numSamples; ++i, --l {
                         newSamples[i] = v
@@ -325,6 +328,8 @@ class ViewControllerSimulator: NSViewController {
                 
                 // append sample buffer
                 if !avWriterInput.appendSampleBuffer(newSampleBuffer!) {
+                    DLog("failed to write sample buffer \(avWriter.status) \(avWriter.error)")
+                    avReader.cancelReading() // cancel reading
                     completedOrFailed = true
                 }
             }
diff --git a/convert_to_text.m b/convert_to_text.m
index 3e1a9c8..74d74d7 100644
--- a/convert_to_text.m
+++ b/convert_to_text.m
@@ -29,9 +29,9 @@ function convert_to_text(fn, mat)
 
 fprintf(fh, '# AUTOMATICALLY GENERATED SYLLABLE DETECTOR CONFIGURATION\n');
 fprintf(fh, 'samplingRate = %.1f\n', f.samplerate);
-fprintf(fh, 'windowLength = %d\n', f.win_size);
 fprintf(fh, 'fourierLength = %d\n', f.fft_size);
-fprintf(fh, 'fourierOverlap = %d\n', f.fft_size - f.fft_time_shift);
+fprintf(fh, 'windowLength = %d\n', f.win_size);
+fprintf(fh, 'windowOverlap = %d\n', f.fft_size - f.fft_time_shift);
 
 fprintf(fh, 'freqRange = %.1f, %.1f\n', f.freq_range(1), f.freq_range(end));
 fprintf(fh, 'timeRange = %d\n', f.time_window_steps);