# HG changeset patch
# User Chris Cannam
# Date 1470064861 -3600
# Node ID 9fb8dfd7ce4c3788e84d8ec28c683b53e0a5bfb1
# Parent  5c3333fb70b3ad19d04e9154c8b60656439288a5
Fix threshold in spectrogram -- it wasn't working in the last release.
There is a new protocol for this. Formerly the threshold parameter had a
range from -50dB to 0 with the default at -50, and -50 treated internally
as "no threshold". However, there was a hardcoded, hidden internal threshold
for spectrogram colour mapping at -80dB with anything below this being rounded
to zero. Now the threshold parameter has range -81 to -1 with the default
at -80, -81 is treated internally as "no threshold", and there is no hidden
internal threshold. So the default behaviour is the same as before, an
effective -80dB threshold, but it is now possible to change this in both
directions. Sessions reloaded from prior versions may look slightly different
because, if the session says there should be no threshold, there will now
actually be no threshold instead of having the hidden internal one.

Still need to do something in the UI to make it apparent that the -81dB
setting removes the threshold entirely. This is at least no worse than the
previous, also obscured, magic -50dB setting.

diff -r 5c3333fb70b3 -r 9fb8dfd7ce4c layer/ColourScale.cpp
--- a/layer/ColourScale.cpp	Mon Aug 01 16:13:29 2016 +0100
+++ b/layer/ColourScale.cpp	Mon Aug 01 16:21:01 2016 +0100
@@ -33,6 +33,10 @@
     m_mappedMin = m_params.minValue;
     m_mappedMax = m_params.maxValue;
 
+    if (m_mappedMin < m_params.threshold) {
+        m_mappedMin = m_params.threshold;
+    }
+    
     if (m_params.scale == ColourScaleType::Log) {
 
 	LogRange::mapRange(m_mappedMin, m_mappedMax);
diff -r 5c3333fb70b3 -r 9fb8dfd7ce4c layer/SpectrogramLayer.cpp
--- a/layer/SpectrogramLayer.cpp	Mon Aug 01 16:13:29 2016 +0100
+++ b/layer/SpectrogramLayer.cpp	Mon Aug 01 16:21:01 2016 +0100
@@ -65,8 +65,8 @@
     m_windowHopLevel(2),
     m_gain(1.0),
     m_initialGain(1.0),
-    m_threshold(0.0),
-    m_initialThreshold(0.0),
+    m_threshold(1.0e-8),
+    m_initialThreshold(1.0e-8),
     m_colourRotation(0),
     m_initialRotation(0),
     m_minFrequency(10),
@@ -304,8 +304,8 @@
 
     } else if (name == "Threshold") {
 
-	*min = -50;
-	*max = 0;
+	*min = -81;
+	*max = -1;
 
         *deflt = int(lrint(AudioLevel::multiplier_to_dB(m_initialThreshold)));
 	if (*deflt < *min) *deflt = *min;
@@ -530,7 +530,7 @@
         return new LinearRangeMapper(-50, 50, -25, 25, tr("dB"));
     }
     if (name == "Threshold") {
-        return new LinearRangeMapper(-50, 0, -50, 0, tr("dB"));
+        return new LinearRangeMapper(-81, -1, -81, -1, tr("dB"));
     }
     return 0;
 }
@@ -541,7 +541,7 @@
     if (name == "Gain") {
 	setGain(float(pow(10, float(value)/20.0)));
     } else if (name == "Threshold") {
-	if (value == -50) setThreshold(0.0);
+	if (value == -81) setThreshold(0.0);
 	else setThreshold(float(AudioLevel::dB_to_multiplier(value)));
     } else if (name == "Colour Rotation") {
 	setColourRotation(value);
@@ -2055,6 +2055,9 @@
         double min = m_viewMags[v->getId()].getMin();
         double max = m_viewMags[v->getId()].getMax();
 
+        if (min < m_threshold) min = m_threshold;
+        if (max < min) max = min;
+        
         double dBmin = AudioLevel::multiplier_to_dB(min);
         double dBmax = AudioLevel::multiplier_to_dB(max);
 
diff -r 5c3333fb70b3 -r 9fb8dfd7ce4c layer/SpectrogramLayer.h
--- a/layer/SpectrogramLayer.h	Mon Aug 01 16:13:29 2016 +0100
+++ b/layer/SpectrogramLayer.h	Mon Aug 01 16:21:01 2016 +0100
@@ -125,7 +125,7 @@
      * Set the threshold for sample values to qualify for being shown
      * in the FFT, in voltage units.
      *
-     * The default is 0.0.
+     * The default is 10^-8 (-80dB).
      */
     void setThreshold(float threshold);
     float getThreshold() const;