Fix key rounding code, returning max + 1.

Originally the chords and the chroma data have 3 bins per key and center at 1.
This means the first correlation matches at 0. To compensate this the chroma
data is shifted on step more. This way we have C wihout wrap around at 0, 1
and 2 and can use integer math to get the final key value.
This was tested with a B minor chord and a 440 Hz (A) and 523,25 Hz (C) sinus.

2 files changed, 35 insertions, 8 deletions

diff --git a/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp b/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
index cf3580e80e..55a13331b9 100644
--- a/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
+++ b/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
@@ -177,12 +177,11 @@ int GetKeyMode::process(double *PCMData)
 

     m_ChrPointer = m_Chroma->process( m_DecimatedBuffer );		

 

-	

-    // Move bins such that the centre of the base note is in the

-    // middle of its three bins :

-    // Added 21.11.07 by Chris Sutton based on debugging with Katy

-    // Noland + comparison with Matlab equivalent.

-    MathUtilities::circShift( m_ChrPointer, m_BPO, 1);

+    // The Cromagram has the center of C at bin 0, while the major

+    // and minor profiles have the center of C at 1. We want to have

+    // the correlation for C result also at 1.

+    // To achieve this we have to shift two times:

+    MathUtilities::circShift( m_ChrPointer, m_BPO, 2);

 /*

     std::cout << "raw chroma: ";

     for (int ii = 0; ii < m_BPO; ++ii) {

@@ -266,8 +265,10 @@ int GetKeyMode::process(double *PCMData)
   std::cout << std::endl;

 */

     double dummy;

-    // '1 +' because we number keys 1-24, not 0-23.

-    key = 1 + (int)ceil( (double)MathUtilities::getMax( m_Keys, 2* m_BPO, &dummy )/3 );

+    // m_Keys[1] is C center  1 / 3 + 1 = 1

+    // m_Keys[4] is D center  4 / 3 + 1 = 2

+    // '+ 1' because we number keys 1-24, not 0-23.

+    key = MathUtilities::getMax( m_Keys, 2* m_BPO, &dummy ) / 3 + 1;

 

 //    std::cout << "key pre-sorting: " << key << std::endl;

 

diff --git a/lib/qm-dsp/key_rounding.patch b/lib/qm-dsp/key_rounding.patch
new file mode 100644
index 0000000000..7f8cfd7540
--- /dev/null
+++ b/lib/qm-dsp/key_rounding.patch
@@ -0,0 +1,26 @@
+diff --git a/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp b/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
+index cf3580e..bf72b21 100644
+--- a/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
++++ b/lib/qm-dsp/dsp/keydetection/GetKeyMode.cpp
+@@ -182,7 +182,7 @@ int GetKeyMode::process(double *PCMData)
+     // middle of its three bins :

+     // Added 21.11.07 by Chris Sutton based on debugging with Katy

+     // Noland + comparison with Matlab equivalent.

+-    MathUtilities::circShift( m_ChrPointer, m_BPO, 1);

++    MathUtilities::circShift( m_ChrPointer, m_BPO, 2);

+ /*

+     std::cout << "raw chroma: ";

+     for (int ii = 0; ii < m_BPO; ++ii) {

+@@ -266,8 +266,10 @@ int GetKeyMode::process(double *PCMData)
+   std::cout << std::endl;

+ */

+     double dummy;

+-    // '1 +' because we number keys 1-24, not 0-23.

+-    key = 1 + (int)ceil( (double)MathUtilities::getMax( m_Keys, 2* m_BPO, &dummy )/3 );

++    // m_Keys[1] is C center  1 / 3 + 1 = 1

++    // m_Keys[4] is D center  4 / 3 + 1 = 2

++    // '+ 1' because we number keys 1-24, not 0-23.

++    key = MathUtilities::getMax( m_Keys, 2* m_BPO, &dummy ) / 3 + 1;

+ 

+ //    std::cout << "key pre-sorting: " << key << std::endl;

+