feat: initial fft spectrum visualization support

The final goal is actually still clone ShadowPlayer's spectrum
visualization, tho.

CMakeLists.txt

@@ -4,6 +4,7 @@ project(pineapple-music LANGUAGES CXX)
 
 include (GNUInstallDirs)
 include (FeatureSummary)
+include(FetchContent)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
@@ -20,6 +21,17 @@ find_package(Qt6 6.6 COMPONENTS Widgets Multimedia Network LinguistTools REQUIRE
 find_package(TagLib 2.0.0)
 find_package(KF6Codecs 6.1.0)
 
+FetchContent_Declare(
+    kissfft
+    GIT_REPOSITORY https://github.com/mborgerding/kissfft.git
+    GIT_TAG f5f2a3b2f2cd02bf80639adb12cbeed125bdf420
+)
+set(KISSFFT_PKGCONFIG OFF CACHE BOOL "dep(kissfft): pkgconfig support")
+set(KISSFFT_STATIC ON CACHE BOOL "dep(kissfft): static linking")
+set(KISSFFT_TEST OFF CACHE BOOL "dep(kissfft): enable testing")
+set(KISSFFT_TOOLS OFF CACHE BOOL "dep(kissfft): build tools")
+FetchContent_MakeAvailable(kissfft)
+
 if (USE_QTEXTCODEC)
     find_package(Qt6 6.6 COMPONENTS Core5Compat REQUIRED)
 endif()
@@ -32,6 +44,7 @@ set (PMUSIC_CPP_FILES
     singleapplicationmanager.cpp
     lrcbar.cpp
     lyricsmanager.cpp
+    fftspectrum.cpp
 )
 
 set (PMUSIC_HEADER_FILES
@@ -41,6 +54,7 @@ set (PMUSIC_HEADER_FILES
     singleapplicationmanager.h
     lrcbar.h
     lyricsmanager.h
+    fftspectrum.h
 )
 
 set (PMUSIC_UI_FILES
@@ -80,7 +94,7 @@ if (TARGET KF6::Codecs)
     target_link_libraries (${EXE_NAME} PRIVATE KF6::Codecs)
 endif ()
 
-target_link_libraries(${EXE_NAME} PRIVATE Qt::Widgets Qt::Multimedia Qt::Network)
+target_link_libraries(${EXE_NAME} PRIVATE Qt::Widgets Qt::Multimedia Qt::Network kissfft::kissfft)
 
 if (USE_QTEXTCODEC)
     target_compile_definitions(${EXE_NAME} PRIVATE USE_QTEXTCODEC=1)

README.md

@@ -2,12 +2,23 @@
 
 Since **I** just need a simple player which *just works* right now, so I did many things in a dirty way. Don't feel so weird if you saw something I did in this project is using a bad approach.
 
-### Feature Notice
+### Features
+
+We have the following features:
+
+- [Sidecar](https://en.wikipedia.org/wiki/Sidecar_file) lyrics file (`.lrc`) support with an optional desktop lyrics bar widget
+- Auto-load all audio files in the same folder of the file that you attempted to play, into a playlist
+
+But these features are not available, some of them are TBD and others are not planned:
 
 - File format support will be limited by the [FFmpeg version that Qt 6 uses](https://doc.qt.io/qt-6/qtmultimedia-attribution-ffmpeg.html).
   - ...which if you use Qt's official binary, only contains the LGPLv2.1+ part. (already good enough, tho)
 - No music library management support and there won't be one!
   - It'll auto-load music files in the same folder of the file that you attempted to play, so organize your music files on a folder-basis.
+- Limited system integration:
+  - No [SMTC](https://learn.microsoft.com/en-us/uwp/api/windows.media.systemmediatransportcontrols) support under Windows for now
+  - No [MPRIS](https://www.freedesktop.org/wiki/Specifications/mpris-spec/) support under Linux desktop for now
+  - No "playback progress on taskbar icon" and "taskbar thumbnail buttons" support whatever on Windows or Linux desktop for now
 - Limited lyrics (`.lrc`) loading support:
   - Currently no `.tlrc` (for translated lyrics) or `.rlrc` (for romanized lyrics) support.
   - Multi-line lyrics and duplicated timestamps are not supported
@@ -20,7 +31,7 @@ Current state, we need:
  - `cmake` as the build system.
  - `qt6` with `qt6-multimedia` since we use it for playback.
  - `taglib` to get the audio file properties.
- - `pkg-config` to find the installed taglib.
+ - `kissfft` for FFT support (will be downloaded at configure-time by `cmake`).
 
 Then we can build it with any proper c++ compiler like g++ or msvc.
 

fftspectrum.cpp

@@ -0,0 +1,124 @@
+// SPDX-FileCopyrightText: 2024 Gary Wang <git@blumia.net>
+//
+// SPDX-License-Identifier: MIT
+
+#include "fftspectrum.h"
+
+#include <QAudioBuffer>
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+#include <QAudioBufferOutput>
+#endif // QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+#include <QPainter>
+
+#include <kissfft.hh>
+
+FFTSpectrum::FFTSpectrum(QWidget* parent)
+    : QWidget(parent)
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    , m_audioBufferOutput(new QAudioBufferOutput(this))
+#endif // #if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    connect(this, &FFTSpectrum::mediaPlayerChanged, this, [=]() {
+        if (m_mediaPlayer) {
+            m_mediaPlayer->setAudioBufferOutput(m_audioBufferOutput);
+        }
+    });
+
+    connect(m_audioBufferOutput, &QAudioBufferOutput::audioBufferReceived, this, [=](const QAudioBuffer& buffer) {
+        const QAudioFormat& fmt = buffer.format();
+        const QAudioFormat::SampleFormat sampleFormat = fmt.sampleFormat();
+        QAudioFormat::ChannelConfig channelConfig = fmt.channelConfig();
+        const QFlags supportedChannelConfig({ QAudioFormat::ChannelConfigMono, QAudioFormat::ChannelConfigStereo });
+        const int frameCount = buffer.frameCount();
+        kissfft<float> fft(frameCount, false);
+        std::vector<kissfft<float>::cpx_t> samples(frameCount);
+        std::vector<kissfft<float>::cpx_t> mass(frameCount);
+        if (sampleFormat == QAudioFormat::Int16 && supportedChannelConfig.testFlag(channelConfig)) {
+            if (channelConfig == QAudioFormat::ChannelConfigMono) {
+                const QAudioBuffer::S16M* data = buffer.constData<QAudioBuffer::S16M>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontCenter) / float(32768));
+                    samples[i].imag(0);
+                }
+            } else {
+                const QAudioBuffer::S16S* data = buffer.constData<QAudioBuffer::S16S>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontLeft) / float(32768));
+                    samples[i].imag(0);
+                }
+            }
+        } else if (sampleFormat == QAudioFormat::Int32 && supportedChannelConfig.testFlag(channelConfig)) {
+            if (channelConfig == QAudioFormat::ChannelConfigMono) {
+                const QAudioBuffer::S32M* data = buffer.constData<QAudioBuffer::S32M>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontCenter) / float(2147483647));
+                    samples[i].imag(0);
+                }
+            } else {
+                const QAudioBuffer::S32S* data = buffer.constData<QAudioBuffer::S32S>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontLeft) / float(2147483647));
+                    samples[i].imag(0);
+                }
+            }
+        } else if (sampleFormat == QAudioFormat::Float && supportedChannelConfig.testFlag(channelConfig)) {
+            if (channelConfig == QAudioFormat::ChannelConfigMono) {
+                const QAudioBuffer::F32M* data = buffer.constData<QAudioBuffer::F32M>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontCenter));
+                    samples[i].imag(0);
+                }
+            } else {
+                const QAudioBuffer::F32S* data = buffer.constData<QAudioBuffer::F32S>();
+                for (int i = 0; i < frameCount; ++i) {
+                    samples[i].real(data[i].value(QAudioFormat::FrontLeft));
+                    samples[i].imag(0);
+                }
+            }
+        } else {
+            qWarning() << "Unsupported format or channel config:" << sampleFormat << channelConfig;
+            return;
+        }
+        fft.transform(samples.data(), mass.data());
+        m_freq.resize(frameCount);
+        for (int i = 0; i < frameCount; i++) {
+            m_freq[i] = sqrt(mass[i].real() * mass[i].real() + mass[i].imag() * mass[i].imag());
+        }
+        for (auto& val : m_freq) {
+            val = log10(val + 1);
+        }
+        qDebug() << m_freq.size() << "updated" << sampleFormat << channelConfig;
+        update();
+    });
+#endif // QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    resize(490, 420);
+}
+
+FFTSpectrum::~FFTSpectrum()
+{
+
+}
+
+void FFTSpectrum::setMediaPlayer(QMediaPlayer* player)
+{
+    m_mediaPlayer = player;
+    emit mediaPlayerChanged();
+}
+
+void FFTSpectrum::paintEvent(QPaintEvent* e)
+{
+    QPainter painter(this);
+
+    if (!m_freq.empty()) {
+        int width = this->width();
+        int height = this->height();
+        int barWidth = std::max(1ULL, width / m_freq.size());
+        for (int i = 0; i < m_freq.size(); i++) {
+            int barHeight = static_cast<int>(sqrt(m_freq[i]) * height * 0.5);
+            painter.fillRect(i * barWidth, height - barHeight, barWidth, barHeight, QColor(70, 130, 180, (int)(140 * m_freq[i]) + 90));
+        }
+    }
+}
+
+

fftspectrum.h

@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: 2024 Gary Wang <git@blumia.net>
+//
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <QWidget>
+#include <QMediaPlayer>
+
+class QAudioBufferOutput;
+class FFTSpectrum : public QWidget
+{
+    Q_OBJECT
+    Q_PROPERTY(QMediaPlayer * mediaPlayer MEMBER m_mediaPlayer WRITE setMediaPlayer NOTIFY mediaPlayerChanged)
+public:
+    explicit FFTSpectrum(QWidget* parent);
+    ~FFTSpectrum();
+
+    void setMediaPlayer(QMediaPlayer* player);
+
+signals:
+    void mediaPlayerChanged();
+
+protected:
+    void paintEvent(QPaintEvent* e) override;
+
+private:
+    QMediaPlayer* m_mediaPlayer = nullptr;
+    QAudioBufferOutput* m_audioBufferOutput = nullptr;
+    std::vector<float> m_freq;
+};

mainwindow.cpp

@@ -6,6 +6,7 @@
 #include "./ui_mainwindow.h"
 
 #include "playlistmanager.h"
+#include "fftspectrum.h"
 #include "lrcbar.h"
 
 // taglib
@@ -41,6 +42,7 @@ MainWindow::MainWindow(QWidget *parent)
     , m_mediaDevices(new QMediaDevices(this))
     , m_mediaPlayer(new QMediaPlayer(this))
     , m_audioOutput(new QAudioOutput(this))
+    , m_fftSpectrum(new FFTSpectrum(this))
     , m_lrcbar(new LrcBar(nullptr))
     , m_playlistManager(new PlaylistManager(this))
 {
@@ -48,6 +50,7 @@ MainWindow::MainWindow(QWidget *parent)
     m_playlistManager->setAutoLoadFilterSuffixes({
         "*.mp3", "*.wav", "*.aiff", "*.ape", "*.flac", "*.ogg", "*.oga", "*.mpga", "*.aac", "*.tta"
     });
+    m_fftSpectrum->setMediaPlayer(m_mediaPlayer);
     m_mediaPlayer->setAudioOutput(m_audioOutput);
     m_mediaPlayer->setLoops(QMediaPlayer::Infinite);
     ui->playlistView->setModel(m_playlistManager->model());

mainwindow.h

@@ -17,6 +17,7 @@ class QAudioOutput;
 class QPropertyAnimation;
 QT_END_NAMESPACE
 
+class FFTSpectrum;
 class LrcBar;
 class PlaylistManager;
 class MainWindow : public QMainWindow
@@ -92,6 +93,7 @@ private:
     QMediaDevices *m_mediaDevices;
     QMediaPlayer *m_mediaPlayer;
     QAudioOutput *m_audioOutput;
+    FFTSpectrum* m_fftSpectrum;
     LrcBar *m_lrcbar;
     QPropertyAnimation *m_fadeOutAnimation;
     PlaylistManager *m_playlistManager;