Added a new class AudioVisualiserComponent, and updated the demo audio pages to use this.

examples/Demo/Source/Demos/AudioLiveScrollingDisplay.h

@@ -32,18 +32,14 @@
 /* This component scrolls a continuous waveform showing the audio that's
    coming into whatever audio inputs this object is connected to.
 */
-class LiveScrollingAudioDisplay  : public Component,
-                                   public AudioIODeviceCallback,
-                                   private Timer
+class LiveScrollingAudioDisplay  : public AudioVisualiserComponent,
+                                   public AudioIODeviceCallback
 {
 public:
-    LiveScrollingAudioDisplay()
-        : nextSample (0), subSample (0), accumulator (0)
+    LiveScrollingAudioDisplay()  : AudioVisualiserComponent (1)
     {
-        setOpaque (true);
-        clear();
-
-        startTimerHz (75); // use a timer to keep repainting this component
+        setSamplesPerBlock (256);
+        setBufferSize (1024);
     }
 
     //==============================================================================
@@ -66,72 +62,18 @@ public:
             float inputSample = 0;
 
             for (int chan = 0; chan < numInputChannels; ++chan)
-                if (inputChannelData[chan] != nullptr)
-                    inputSample += std::abs (inputChannelData[chan][i]);  // find the sum of all the channels
+                if (const float* inputChannel = inputChannelData[chan])
+                    inputSample += inputChannel[i];  // find the sum of all the channels
 
-            pushSample (10.0f * inputSample); // boost the level to make it more easily visible.
+            inputSample *= 10.0f; // boost the level to make it more easily visible.
+
+            pushSample (&inputSample, 1);
         }
 
         // We need to clear the output buffers before returning, in case they're full of junk..
         for (int j = 0; j < numOutputChannels; ++j)
-            if (outputChannelData[j] != nullptr)
-                zeromem (outputChannelData[j], sizeof (float) * (size_t) numSamples);
-    }
-
-private:
-    float samples[1024];
-    int nextSample, subSample;
-    float accumulator;
-
-    void clear()
-    {
-        zeromem (samples, sizeof (samples));
-        accumulator = 0;
-        subSample = 0;
-    }
-
-    void paint (Graphics& g) override
-    {
-        g.fillAll (Colours::black);
-
-        const float midY = getHeight() * 0.5f;
-        int samplesAgo = (nextSample + numElementsInArray (samples) - 1);
-
-        RectangleList<float> waveform;
-        waveform.ensureStorageAllocated ((int) numElementsInArray (samples));
-
-        for (int x = jmin (getWidth(), (int) numElementsInArray (samples)); --x >= 0;)
-        {
-            const float sampleSize = midY * samples [samplesAgo-- % numElementsInArray (samples)];
-            waveform.addWithoutMerging (Rectangle<float> ((float) x, midY - sampleSize, 1.0f, sampleSize * 2.0f));
-        }
-
-        g.setColour (Colours::lightgreen);
-        g.fillRectList (waveform);
-    }
-
-    void timerCallback() override
-    {
-        repaint();
-    }
-
-    void pushSample (const float newSample)
-    {
-        accumulator += newSample;
-
-        if (subSample == 0)
-        {
-            const int inputSamplesPerPixel = 200;
-
-            samples[nextSample] = accumulator / inputSamplesPerPixel;
-            nextSample = (nextSample + 1) % numElementsInArray (samples);
-            subSample = inputSamplesPerPixel;
-            accumulator = 0;
-        }
-        else
-        {
-            --subSample;
-        }
+            if (float* outputChannel = outputChannelData[j])
+                zeromem (outputChannel, sizeof (float) * (size_t) numSamples);
     }
 
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (LiveScrollingAudioDisplay);

modules/juce_audio_utils/gui/juce_AudioVisualiserComponent.cpp

@@ -0,0 +1,220 @@
+/*
+  ==============================================================================
+
+   This file is part of the JUCE library.
+   Copyright (c) 2015 - ROLI Ltd.
+
+   Permission is granted to use this software under the terms of either:
+   a) the GPL v2 (or any later version)
+   b) the Affero GPL v3
+
+   Details of these licenses can be found at: www.gnu.org/licenses
+
+   JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   ------------------------------------------------------------------------------
+
+   To release a closed-source product which uses JUCE, commercial licenses are
+   available: visit www.juce.com for more information.
+
+  ==============================================================================
+*/
+
+struct AudioVisualiserComponent::ChannelInfo
+{
+    ChannelInfo (AudioVisualiserComponent& o, int bufferSize)
+       : owner (o), nextSample (0), subSample (0)
+    {
+        setBufferSize (bufferSize);
+        clear();
+    }
+
+    void clear() noexcept
+    {
+        for (int i = 0; i < levels.size(); ++i)
+            levels.getReference(i) = Range<float>();
+
+        value = Range<float>();
+        subSample = 0;
+    }
+
+    void pushSamples (const float* inputSamples, const int num) noexcept
+    {
+        for (int i = 0; i < num; ++i)
+            pushSample (inputSamples[i]);
+    }
+
+    void pushSample (const float newSample) noexcept
+    {
+        if (--subSample <= 0)
+        {
+            nextSample %= levels.size();
+            levels.getReference (nextSample++) = value;
+            subSample = owner.getSamplesPerBlock();
+            value = Range<float> (newSample, newSample);
+        }
+        else
+        {
+            value = value.getUnionWith (newSample);
+        }
+    }
+
+    void setBufferSize (int newSize)
+    {
+        levels.removeRange (newSize, levels.size());
+        levels.insertMultiple (-1, Range<float>(), newSize - levels.size());
+
+        if (nextSample >= newSize)
+            nextSample = 0;
+    }
+
+    AudioVisualiserComponent& owner;
+    Array<Range<float> > levels;
+    Range<float> value;
+    int nextSample, subSample;
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ChannelInfo);
+};
+
+//==============================================================================
+AudioVisualiserComponent::AudioVisualiserComponent (const int initialNumChannels)
+  : numSamples (1024),
+    inputSamplesPerBlock (256),
+    backgroundColour (Colours::black),
+    waveformColour (Colours::white)
+{
+    setOpaque (true);
+    setNumChannels (initialNumChannels);
+    setRepaintRate (60);
+}
+
+AudioVisualiserComponent::~AudioVisualiserComponent()
+{
+}
+
+void AudioVisualiserComponent::setNumChannels (const int numChannels)
+{
+    channels.clear();
+
+    for (int i = 0; i < numChannels; ++i)
+        channels.add (new ChannelInfo (*this, numSamples));
+}
+
+void AudioVisualiserComponent::setBufferSize (int newNumSamples)
+{
+    numSamples = newNumSamples;
+
+    for (int i = 0; i < channels.size(); ++i)
+        channels.getUnchecked(i)->setBufferSize (newNumSamples);
+}
+
+void AudioVisualiserComponent::clear()
+{
+    for (int i = 0; i < channels.size(); ++i)
+        channels.getUnchecked(i)->clear();
+}
+
+void AudioVisualiserComponent::pushBuffer (const float** d, int numChannels, int num)
+{
+    numChannels = jmin (numChannels, channels.size());
+
+    for (int i = 0; i < numChannels; ++i)
+        channels.getUnchecked(i)->pushSamples (d[i], num);
+}
+
+void AudioVisualiserComponent::pushBuffer (const AudioSampleBuffer& buffer)
+{
+    pushBuffer (buffer.getArrayOfReadPointers(),
+                buffer.getNumChannels(),
+                buffer.getNumSamples());
+}
+
+void AudioVisualiserComponent::pushBuffer (const AudioSourceChannelInfo& buffer)
+{
+    const int numChannels = jmin (buffer.buffer->getNumChannels(), channels.size());
+
+    for (int i = 0; i < numChannels; ++i)
+        channels.getUnchecked(i)->pushSamples (buffer.buffer->getReadPointer (i, buffer.startSample),
+                                               buffer.numSamples);
+}
+
+void AudioVisualiserComponent::pushSample (const float* d, int numChannels)
+{
+    numChannels = jmin (numChannels, channels.size());
+
+    for (int i = 0; i < numChannels; ++i)
+        channels.getUnchecked(i)->pushSample (d[i]);
+}
+
+void AudioVisualiserComponent::setSamplesPerBlock (int newSamplesPerPixel) noexcept
+{
+    inputSamplesPerBlock = newSamplesPerPixel;
+}
+
+void AudioVisualiserComponent::setRepaintRate (int frequencyInHz)
+{
+    startTimerHz (frequencyInHz);
+}
+
+void AudioVisualiserComponent::timerCallback()
+{
+    repaint();
+}
+
+void AudioVisualiserComponent::setColours (Colour bk, Colour fg) noexcept
+{
+    backgroundColour = bk;
+    waveformColour = fg;
+    repaint();
+}
+
+void AudioVisualiserComponent::paint (Graphics& g)
+{
+    g.fillAll (backgroundColour);
+
+    Rectangle<float> r (getLocalBounds().toFloat());
+    const float channelHeight = r.getHeight() / channels.size();
+
+    g.setColour (waveformColour);
+
+    for (int i = 0; i < channels.size(); ++i)
+    {
+        const ChannelInfo& c = *channels.getUnchecked(i);
+
+        paintChannel (g, r.removeFromTop (channelHeight),
+                      c.levels.begin(), c.levels.size(), c.nextSample);
+    }
+}
+
+void AudioVisualiserComponent::getChannelAsPath (Path& path, const Range<float>* levels, int numLevels, int nextSample)
+{
+    path.preallocateSpace (4 * numLevels + 8);
+
+    for (int i = 0; i < numLevels; ++i)
+    {
+        const float level = -(levels[(nextSample + i) % numLevels].getEnd());
+
+        if (i == 0)
+            path.startNewSubPath (0.0f, level);
+        else
+            path.lineTo ((float) i, level);
+    }
+
+    for (int i = numLevels; --i >= 0;)
+        path.lineTo ((float) i, -(levels[(nextSample + i) % numLevels].getStart()));
+
+    path.closeSubPath();
+}
+
+void AudioVisualiserComponent::paintChannel (Graphics& g, Rectangle<float> bounds,
+                                             const Range<float>* levels, int numLevels, int nextSample)
+{
+    Path p;
+    getChannelAsPath (p, levels, numLevels, nextSample);
+
+    g.fillPath (p, AffineTransform::fromTargetPoints (0.0f, -1.0f,      bounds.getX(), bounds.getY(),
+                                                      0.0f, 1.0f,       bounds.getX(), bounds.getBottom(),
+                                                      numLevels, -1.0f, bounds.getRight(), bounds.getY()));
+}

modules/juce_audio_utils/gui/juce_AudioVisualiserComponent.h

@@ -0,0 +1,135 @@
+/*
+  ==============================================================================
+
+   This file is part of the JUCE library.
+   Copyright (c) 2015 - ROLI Ltd.
+
+   Permission is granted to use this software under the terms of either:
+   a) the GPL v2 (or any later version)
+   b) the Affero GPL v3
+
+   Details of these licenses can be found at: www.gnu.org/licenses
+
+   JUCE is distributed in the hope that it will be useful, but WITHOUT ANY
+   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+   ------------------------------------------------------------------------------
+
+   To release a closed-source product which uses JUCE, commercial licenses are
+   available: visit www.juce.com for more information.
+
+  ==============================================================================
+*/
+
+#ifndef JUCE_AUDIOVISUALISER_H_INCLUDED
+#define JUCE_AUDIOVISUALISER_H_INCLUDED
+
+
+//==============================================================================
+/**
+    A simple component that can be used to show a scrolling waveform of audio data.
+
+    This is a handy way to get a quick visualisation of some audio data. Just create
+    one of these, set its size and oversampling rate, and then feed it with incoming
+    data by calling one of its pushBuffer() or pushSample() methods.
+
+    You can override its paint method for more customised views, but it's only designed
+    as a quick-and-dirty class for simple tasks, so please don't send us feature requests
+    for fancy additional features that you'd like it to support! If you're building a
+    real-world app that requires more powerful waveform display, you'll probably want to
+    create your own component instead.
+*/
+class AudioVisualiserComponent  : public Component,
+                                  private Timer
+{
+public:
+    /** Creates a visualiser with the given number of channels. */
+    AudioVisualiserComponent (int initialNumChannels);
+
+    /** Destructor. */
+    ~AudioVisualiserComponent();
+
+    /** Changes the number of channels that the visualiser stores. */
+    void setNumChannels (int numChannels);
+
+    /** Changes the number of samples that the visualiser keeps in its history.
+        Note that this value refers to the number of averaged sample blocks, and each
+        block is calculated as the peak of a number of incoming audio samples. To set
+        the number of incoming samples per block, use setSamplesPerBlock().
+     */
+    void setBufferSize (int bufferSize);
+
+    /** */
+    void setSamplesPerBlock (int newNumInputSamplesPerBlock) noexcept;
+
+    /** */
+    int getSamplesPerBlock() const noexcept                         { return inputSamplesPerBlock; }
+
+    /** Clears the contents of the buffers. */
+    void clear();
+
+    /** Pushes a buffer of channels data.
+        The number of channels provided here is expected to match the number of channels
+        that this AudioVisualiserComponent has been told to use.
+    */
+    void pushBuffer (const AudioSampleBuffer& bufferToPush);
+
+    /** Pushes a buffer of channels data.
+        The number of channels provided here is expected to match the number of channels
+        that this AudioVisualiserComponent has been told to use.
+    */
+    void pushBuffer (const AudioSourceChannelInfo& bufferToPush);
+
+    /** Pushes a buffer of channels data.
+        The number of channels provided here is expected to match the number of channels
+        that this AudioVisualiserComponent has been told to use.
+    */
+    void pushBuffer (const float** channelData, int numChannels, int numSamples);
+
+    /** Pushes a single sample (per channel).
+        The number of channels provided here is expected to match the number of channels
+        that this AudioVisualiserComponent has been told to use.
+    */
+    void pushSample (const float* samplesForEachChannel, int numChannels);
+
+    /** Sets the colours used to paint the */
+    void setColours (Colour backgroundColour, Colour waveformColour) noexcept;
+
+    /** Sets the frequency at which the component repaints itself. */
+    void setRepaintRate (int frequencyInHz);
+
+    /** Draws a channel of audio data in the given bounds.
+        The default implementation just calls getChannelAsPath() and fits this into the given
+        area. You may want to override this to draw things differently.
+    */
+    virtual void paintChannel (Graphics&, Rectangle<float> bounds,
+                               const Range<float>* levels, int numLevels, int nextSample);
+
+    /** Creates a path which contains the waveform shape of a given set of range data.
+        The path is normalised so that -1 and +1 are its upper and lower bounds, and it
+        goes from 0 to numLevels on the X axis.
+    */
+    void getChannelAsPath (Path& result, const Range<float>* levels, int numLevels, int nextSample);
+
+    //==========================================================================
+    /** @internal */
+    void paint (Graphics&) override;
+
+private:
+    struct ChannelInfo;
+    friend struct ChannelInfo;
+    friend struct ContainerDeletePolicy<ChannelInfo>;
+
+    OwnedArray<ChannelInfo> channels;
+    int numSamples, inputSamplesPerBlock;
+    float interpolation;
+    Colour backgroundColour, waveformColour;
+
+    void timerCallback() override;
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AudioVisualiserComponent);
+};
+
+
+#endif  // JUCE_AUDIOVISUALISER_H_INCLUDED

modules/juce_audio_utils/juce_audio_utils.cpp

@@ -44,6 +44,7 @@ namespace juce
 #include "gui/juce_AudioDeviceSelectorComponent.cpp"
 #include "gui/juce_AudioThumbnail.cpp"
 #include "gui/juce_AudioThumbnailCache.cpp"
+#include "gui/juce_AudioVisualiserComponent.cpp"
 #include "gui/juce_MidiKeyboardComponent.cpp"
 #include "gui/juce_AudioAppComponent.cpp"
 #include "players/juce_AudioProcessorPlayer.cpp"

modules/juce_audio_utils/juce_audio_utils.h

@@ -38,6 +38,7 @@ namespace juce
 #include "gui/juce_AudioThumbnailBase.h"
 #include "gui/juce_AudioThumbnail.h"
 #include "gui/juce_AudioThumbnailCache.h"
+#include "gui/juce_AudioVisualiserComponent.h"
 #include "gui/juce_MidiKeyboardComponent.h"
 #include "gui/juce_AudioAppComponent.h"
 #include "players/juce_AudioProcessorPlayer.h"