MythMusic: Add a 88-Key Piano Visualization

Basically, it's a spectrum analyzer that detects frequencies specifically at
the pitches of a piano keyboard, and then displays the notes being pressed on
a piano keyboard displayed across the screen. Thanks to Martin Andrews for the
patch. Closes #10214.

Note: Edited slightly to match our coding standards.
Signed-off-by: Paul Harrison <pharrison@mythtv.org>

mythplugins/mythmusic/mythmusic/mainvisual.cpp

@@ -78,7 +78,7 @@ void VisualBase::drawWarning(QPainter *p, const QColor &back, const QSize &size,
 }
 
 MainVisual::MainVisual(QWidget *parent, const char *name)
-    : QWidget(parent), vis(0), playing(false), fps(20),
+    : QWidget(parent), vis(0), playing(false), fps(20), samples(SAMPLES_DEFAULT_SIZE),
       timer (0), bannerTimer(0), info_widget(0)
 {
     setObjectName(name);
@@ -144,6 +144,7 @@ void MainVisual::setVisual(const QString &name)
             vis = pVisFactory->create(this, (long int) winId(), pluginName);
             vis->resize(size());
             fps = vis->getDesiredFPS();
+            samples = vis->getDesiredSamples();
             break;
         }
     }
@@ -163,44 +164,46 @@ void MainVisual::prepare()
     }
 }
 
+// This is called via : mythtv/libs/libmyth/output.cpp :: OutputListeners::dispatchVisual
+//    from : mythtv/libs/libmyth/audio/audiooutputbase.cpp :: AudioOutputBase::AddData
 // Caller holds mutex() lock
-void MainVisual::add(uchar *b, unsigned long b_len, unsigned long w, int c, int p)
+void MainVisual::add(uchar *buffer, unsigned long b_len, unsigned long timecode, int source_channels, int bits_per_sample)
 {
-    long len = b_len, cnt;
+    unsigned long len = b_len, cnt;
     short *l = 0, *r = 0;
 
-    len /= c;
-    len /= (p / 8);
+    // len is length of buffer in fully converted samples
+    len /= source_channels;
+    len /= (bits_per_sample / 8);
 
-#define SAMPLES 512
-    if (len > SAMPLES)
-        len = SAMPLES;
+    if (len > samples)
+        len = samples;
 
     cnt = len;
 
-    if (c == 2)
+    if (source_channels == 2)
     {
         l = new short[len];
         r = new short[len];
 
-        if (p == 8)
-            stereo16_from_stereopcm8(l, r, b, cnt);
-        else if (p == 16)
-            stereo16_from_stereopcm16(l, r, (short *) b, cnt);
+        if (bits_per_sample == 8)
+            stereo16_from_stereopcm8(l, r, buffer, cnt);
+        else if (bits_per_sample == 16)
+            stereo16_from_stereopcm16(l, r, (short *) buffer, cnt);
     }
-    else if (c == 1)
+    else if (source_channels == 1)
     {
         l = new short[len];
 
-        if (p == 8)
-            mono16_from_monopcm8(l, b, cnt);
-        else if (p == 16)
-            mono16_from_monopcm16(l, (short *) b, cnt);
+        if (bits_per_sample == 8)
+            mono16_from_monopcm8(l, buffer, cnt);
+        else if (bits_per_sample == 16)
+            mono16_from_monopcm16(l, (short *) buffer, cnt);
     }
     else
         len = 0;
 
-    nodes.append(new VisualNode(l, r, len, w));
+    nodes.append(new VisualNode(l, r, len, timecode));
 }
 
 void MainVisual::timeout()
@@ -220,6 +223,9 @@ void MainVisual::timeout()
                 break;
             nodes.pop_front();
 
+            if (vis)
+                vis->processUndisplayed(node);
+
             delete node;
             node = n;
         }
@@ -233,7 +239,7 @@ void MainVisual::timeout()
         stop = vis->process(node);
         QPainter p(&pixmap);
         if (vis->draw(&p, Qt::black))
-            update();
+            update();  // This implictly picks up the data in pixmap, filled in by draw
     }
 
     if (!playing && stop)
@@ -519,7 +525,7 @@ bool StereoScope::process( VisualNode *node )
 
     if (node) {
         double index = 0;
-        double const step = (double)SAMPLES / size.width();
+        double const step = (double)SAMPLES_DEFAULT_SIZE / size.width();
         for ( int i = 0; i < size.width(); i++) {
             unsigned long indexTo = (unsigned long)(index + step);
             if (indexTo == (unsigned long)(index))
@@ -722,7 +728,7 @@ bool MonoScope::process( VisualNode *node )
     if (node)
     {
         double index = 0;
-        double const step = (double)SAMPLES / size.width();
+        double const step = (double)SAMPLES_DEFAULT_SIZE / size.width();
         for (int i = 0; i < size.width(); i++)
         {
             unsigned long indexTo = (unsigned long)(index + step);

mythplugins/mythmusic/mythmusic/mainvisual.h

@@ -32,6 +32,8 @@ class InfoWidget;
 class Metadata;
 class MainVisual;
 
+#define SAMPLES_DEFAULT_SIZE 512
+
 class VisualNode
 {
 public:
@@ -60,10 +62,20 @@ class VisualBase
 
     // return true if the output should stop
     virtual bool process( VisualNode *node ) = 0;
+
+    // this is called on nodes that will not be displayed :: Not needed for most visualizations
+    // (i.e. between the displayed frames, if you need the whole audio stream)
+    virtual bool processUndisplayed( VisualNode * )
+    {
+        return true; // By default this does nothing : Ignore the in-between chunks of audio data
+    };
+
     virtual bool draw( QPainter *, const QColor & ) = 0;
     virtual void resize( const QSize &size ) = 0;
     virtual void handleKeyPress(const QString &action) = 0;
     virtual int getDesiredFPS(void) { return fps; }
+    // Override this if you need the potential of capturing more data than the default
+    virtual unsigned long getDesiredSamples(void) { return SAMPLES_DEFAULT_SIZE; }
     void drawWarning(QPainter *, const QColor &, const QSize &, QString);
 
   protected:
@@ -133,6 +145,7 @@ public slots:
     QList<VisualNode*> nodes;
     bool playing;
     int fps;
+    unsigned long samples;
     QTimer *timer;
     QTimer *bannerTimer;
     InfoWidget* info_widget;