Adjustments in beat detection

2 files changed, 34 insertions, 44 deletions

diff --git a/source/SoundTouch/BPMDetect.cpp b/source/SoundTouch/BPMDetect.cpp
index 8b3d1c6..c36661f 100644
--- a/source/SoundTouch/BPMDetect.cpp
+++ b/source/SoundTouch/BPMDetect.cpp
@@ -117,23 +117,19 @@ BPMDetect::BPMDetect(int numChannels, int aSampleRate)
 

     envelopeAccu = 0;

 

-    // Initialize RMS volume accumulator to RMS level of 3000 (out of 32768) that's

-    // a typical RMS signal level value for song data. This value is then adapted

+    // Initialize RMS volume accumulator to RMS level of 1500 (out of 32768) that's

+    // safe initial RMS signal level value for song data. This value is then adapted

     // to the actual level during processing.

 #ifdef SOUNDTOUCH_INTEGER_SAMPLES

     // integer samples

-    RMSVolumeAccu = (3000 * 3000) / avgnorm;

+    RMSVolumeAccu = (1500 * 1500) / avgnorm;

 #else

     // float samples, scaled to range [-1..+1[

-    RMSVolumeAccu = (0.092f * 0.092f) / avgnorm;

+    RMSVolumeAccu = (0.045f * 0.045f) / avgnorm;

 #endif

 

-    cutCoeff = 1.75;

-    aboveCutAccu = 0;

-    totalAccu = 0;

-

-    // choose decimation factor so that result is approx. 500 Hz

-    decimateBy = sampleRate / 500;

+    // choose decimation factor so that result is approx. 1000 Hz

+    decimateBy = sampleRate / 1000;

     assert(decimateBy > 0);

     assert(INPUT_BLOCK_SAMPLES < decimateBy * DECIMATED_BLOCK_SAMPLES);

 

@@ -270,31 +266,11 @@ void BPMDetect::calcEnvelope(SAMPLETYPE *samples, int numsamples)
 

         // cut amplitudes that are below cutoff ~2 times RMS volume

         // (we're interested in peak values, not the silent moments)

-        val -= cutCoeff * sqrt(RMSVolumeAccu * avgnorm);

-        if (val > 0)

-        {

-            aboveCutAccu += 1.0;  // sample above threshold

-        }

-        else

+        if (val < 0.5 * sqrt(RMSVolumeAccu * avgnorm))

         {

             val = 0;

         }

 

-        totalAccu += 1.0;

-

-        // maintain sliding statistic what proportion of 'val' samples is

-        // above cutoff threshold

-        aboveCutAccu *= 0.99931;  // 2 sec time constant

-        totalAccu *= 0.99931;

-

-        if (totalAccu > 500)

-        {

-            // after initial settling, auto-adjust cutoff level so that ~8% of 

-            // values are above the threshold

-            double d = (aboveCutAccu / totalAccu) - 0.08;

-            cutCoeff += 0.001 * d;

-        }

-

         // smooth amplitude envelope

         envelopeAccu *= decay;

         envelopeAccu += val;

@@ -306,12 +282,6 @@ void BPMDetect::calcEnvelope(SAMPLETYPE *samples, int numsamples)
 #endif // SOUNDTOUCH_INTEGER_SAMPLES

         samples[i] = (SAMPLETYPE)out;

     }

-

-    // check that cutoff doesn't get too small - it can be just silent sequence!

-    if (cutCoeff < 1.5) 

-    {

-        cutCoeff = 1.5;

-    }

 }

 

 

@@ -355,6 +325,26 @@ void BPMDetect::inputSamples(const SAMPLETYPE *samples, int numSamples)
 

 

 

+void BPMDetect::removeBias()

+{

+    int i;

+    float minval = 1e12f;   // arbitrary large number

+

+    for (i = windowStart; i < windowLen; i ++)

+    {

+        if (xcorr[i] < minval)

+        {

+            minval = xcorr[i];

+        }

+    }

+

+    for (i = windowStart; i < windowLen; i ++)

+    {

+        xcorr[i] -= minval;

+    }

+}

+

+

 float BPMDetect::getBpm()

 {

     double peakPos;

@@ -366,6 +356,9 @@ float BPMDetect::getBpm()
     // save bpm debug analysis data if debug data enabled

     _SaveDebugData(xcorr, windowStart, windowLen, coeff);

 

+    // remove bias from xcorr data

+    removeBias();

+

     // find peak position

     peakPos = peakFinder.detectPeak(xcorr, windowStart, windowLen);

 

diff --git a/source/SoundTouch/PeakFinder.cpp b/source/SoundTouch/PeakFinder.cpp
index 7f70c3c..c5123f0 100644
--- a/source/SoundTouch/PeakFinder.cpp
+++ b/source/SoundTouch/PeakFinder.cpp
@@ -103,7 +103,7 @@ int PeakFinder::findGround(const float *data, int peakpos, int direction) const
 

     pos = peakpos;

 

-    while ((pos > minPos) && (pos < maxPos))

+    while ((pos > minPos+1) && (pos < maxPos-1))

     {

         int prevpos;

 

@@ -132,7 +132,7 @@ int PeakFinder::findGround(const float *data, int peakpos, int direction) const
         {

             // going uphill, increase climbing counter

             climb_count ++;

-            if (climb_count >= 10) break;    // we've been climbing too long => it's next uphill => quit

+            if (climb_count > 5) break;    // we've been climbing too long => it's next uphill => quit

         }

     }

     return lowpos;

@@ -192,12 +192,9 @@ double PeakFinder::getPeakCenter(const float *data, int peakpos) const
     gp1 = findGround(data, peakpos, -1);

     gp2 = findGround(data, peakpos, 1);

 

-    groundLevel = max(data[gp1], data[gp2]);

+    groundLevel = 0.5 * (data[gp1] + data[gp2]);

     peakLevel = data[peakpos];

 

-    if (groundLevel < 1e-9) return 0;                // ground level too small => detection failed

-    if ((peakLevel / groundLevel) < 1.3) return 0;   // peak less than 30% of the ground level => no good peak detected

-

     // calculate 70%-level of the peak

     cutLevel = 0.70f * peakLevel + 0.30f * groundLevel;

     // find mid-level crossings

@@ -269,7 +266,7 @@ double PeakFinder::detectPeak(const float *data, int aminPos, int amaxPos)
         // now compare to highest detected peak

         i1 = (int)(highPeak + 0.5);

         i2 = (int)(peaktmp + 0.5);

-        if (data[i2] >= 0.5*data[i1])

+        if (data[i2] >= 0.4*data[i1])

         {

             // The harmonic is at least half as high primary peak,

             // thus use the harmonic peak instead