Qt 多媒體開發：音頻與視頻處理

Qt 多媒體模塊提供了一套完整的 API，用于開發音頻和視頻處理應用。從簡單的媒體播放到復雜的音視頻編輯，Qt 都提供了相應的工具和組件。本文將從基礎到高級全面解析 Qt 多媒體開發。

一、Qt 多媒體模塊概述

1. 主要組件

Qt 多媒體模塊包含以下核心組件：

QMediaPlayer：音頻/視頻播放器，支持多種格式
QMediaRecorder：媒體錄制器，用于錄制音頻或視頻
QCamera：攝像頭訪問和控制
QAudioInput/QAudioOutput：低級別音頻輸入/輸出
QVideoWidget：視頻顯示組件
QMediaPlaylist：播放列表管理
QSoundEffect：簡單音效播放（低延遲）

2. 平臺支持

Qt 多媒體模塊在不同平臺上依賴于底層的多媒體框架：

Windows：DirectShow、Media Foundation
macOS：QuickTime、AVFoundation
Linux：GStreamer
Android：Android Media Framework
iOS：AVFoundation

二、基礎應用：音頻與視頻播放

1. 簡單音頻播放器

#include <QApplication>
#include <QMediaPlayer>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *layout = new QVBoxLayout(&window);// 創建媒體播放器QMediaPlayer *player = new QMediaPlayer;player->setMedia(QUrl::fromLocalFile("/path/to/music.mp3"));// 創建播放按鈕QPushButton *playButton = new QPushButton("Play");QObject::connect(playButton, &QPushButton::clicked, player, &QMediaPlayer::play);// 創建暫停按鈕QPushButton *pauseButton = new QPushButton("Pause");QObject::connect(pauseButton, &QPushButton::clicked, player, &QMediaPlayer::pause);// 創建停止按鈕QPushButton *stopButton = new QPushButton("Stop");QObject::connect(stopButton, &QPushButton::clicked, player, &QMediaPlayer::stop);// 添加按鈕到布局layout->addWidget(playButton);layout->addWidget(pauseButton);layout->addWidget(stopButton);// 顯示窗口window.show();return a.exec();
}

2. 視頻播放器

#include <QApplication>
#include <QMediaPlayer>
#include <QVideoWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QSlider>
#include <QFileDialog>int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *mainLayout = new QVBoxLayout(&window);QHBoxLayout *controlLayout = new QHBoxLayout;// 創建媒體播放器QMediaPlayer *player = new QMediaPlayer;// 創建視頻顯示組件QVideoWidget *videoWidget = new QVideoWidget;player->setVideoOutput(videoWidget);// 創建控制按鈕QPushButton *openButton = new QPushButton("Open");QPushButton *playButton = new QPushButton("Play");QPushButton *pauseButton = new QPushButton("Pause");QPushButton *stopButton = new QPushButton("Stop");// 創建進度條QSlider *positionSlider = new QSlider(Qt::Horizontal);// 添加控件到布局controlLayout->addWidget(openButton);controlLayout->addWidget(playButton);controlLayout->addWidget(pauseButton);controlLayout->addWidget(stopButton);controlLayout->addWidget(positionSlider);mainLayout->addWidget(videoWidget);mainLayout->addLayout(controlLayout);// 連接信號和槽QObject::connect(openButton, &QPushButton::clicked, [player]() {QString fileName = QFileDialog::getOpenFileName(nullptr, "Open Video File");if (!fileName.isEmpty()) {player->setMedia(QUrl::fromLocalFile(fileName));player->play();}});QObject::connect(playButton, &QPushButton::clicked, player, &QMediaPlayer::play);QObject::connect(pauseButton, &QPushButton::clicked, player, &QMediaPlayer::pause);QObject::connect(stopButton, &QPushButton::clicked, player, &QMediaPlayer::stop);// 更新進度條QObject::connect(player, &QMediaPlayer::positionChanged, positionSlider, &QSlider::setValue);QObject::connect(positionSlider, &QSlider::sliderMoved, player, &QMediaPlayer::setPosition);// 顯示窗口window.show();return a.exec();
}

三、高級功能：音頻處理與錄制

1. 音頻錄制

#include <QApplication>
#include <QMediaRecorder>
#include <QAudioEncoderSettings>
#include <QVideoEncoderSettings>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>
#include <QFileDialog>int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *layout = new QVBoxLayout(&window);// 創建媒體錄制器QMediaRecorder *recorder = new QMediaRecorder;// 設置音頻編碼參數QAudioEncoderSettings audioSettings;audioSettings.setCodec("audio/mp3");audioSettings.setQuality(QMultimedia::HighQuality);recorder->setAudioSettings(audioSettings);// 創建錄制按鈕QPushButton *recordButton = new QPushButton("Record");QObject::connect(recordButton, &QPushButton::clicked, [recorder]() {QString fileName = QFileDialog::getSaveFileName(nullptr, "Save Audio", "", "Audio Files (*.mp3)");if (!fileName.isEmpty()) {recorder->setOutputLocation(QUrl::fromLocalFile(fileName));recorder->record();}});// 創建停止按鈕QPushButton *stopButton = new QPushButton("Stop");QObject::connect(stopButton, &QPushButton::clicked, recorder, &QMediaRecorder::stop);// 添加按鈕到布局layout->addWidget(recordButton);layout->addWidget(stopButton);// 顯示窗口window.show();return a.exec();
}

2. 低級別音頻處理（生成音調）

#include <QApplication>
#include <QAudioOutput>
#include <QBuffer>
#include <QVector>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>// 生成正弦波音頻數據
QByteArray generateTone(int sampleRate, int frequency, int durationMs)
{const int sampleCount = sampleRate * durationMs / 1000;const double twoPi = 2.0 * M_PI;const double amplitude = 32760.0;  // 16位音頻的最大振幅QVector<qint16> samples(sampleCount);// 生成正弦波for (int i = 0; i < sampleCount; ++i) {samples[i] = static_cast<qint16>(amplitude * qSin(twoPi * frequency * i / sampleRate));}// 轉換為字節數組QByteArray data;data.resize(samples.size() * sizeof(qint16));memcpy(data.data(), samples.data(), data.size());return data;
}int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *layout = new QVBoxLayout(&window);// 音頻格式設置QAudioFormat format;format.setSampleRate(44100);format.setChannelCount(1);format.setSampleSize(16);format.setCodec("audio/pcm");format.setByteOrder(QAudioFormat::LittleEndian);format.setSampleType(QAudioFormat::SignedInt);// 創建音頻輸出QAudioOutput *audioOutput = new QAudioOutput(format);// 生成音頻數據（440Hz 音調，持續1秒）QByteArray audioData = generateTone(44100, 440, 1000);// 創建數據緩沖區QBuffer *buffer = new QBuffer(&audioOutput);buffer->setData(audioData);buffer->open(QIODevice::ReadOnly);// 創建播放按鈕QPushButton *playButton = new QPushButton("Play Tone");QObject::connect(playButton, &QPushButton::clicked, [audioOutput, buffer]() {buffer->seek(0);audioOutput->start(buffer);});// 添加按鈕到布局layout->addWidget(playButton);// 顯示窗口window.show();return a.exec();
}

四、視頻處理與攝像頭應用

1. 攝像頭捕獲

#include <QApplication>
#include <QCamera>
#include <QCameraViewfinder>
#include <QCameraImageCapture>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>
#include <QFileDialog>int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *layout = new QVBoxLayout(&window);// 創建攝像頭QCamera *camera = new QCamera;// 創建取景器QCameraViewfinder *viewfinder = new QCameraViewfinder;camera->setViewfinder(viewfinder);// 創建圖像捕獲器QCameraImageCapture *imageCapture = new QCameraImageCapture(camera);// 創建拍照按鈕QPushButton *captureButton = new QPushButton("Capture");QObject::connect(captureButton, &QPushButton::clicked, [imageCapture]() {QString fileName = QFileDialog::getSaveFileName(nullptr, "Save Image", "", "Image Files (*.jpg)");if (!fileName.isEmpty()) {imageCapture->capture(fileName);}});// 添加控件到布局layout->addWidget(viewfinder);layout->addWidget(captureButton);// 啟動攝像頭camera->start();// 顯示窗口window.show();return a.exec();
}

2. 視頻幀處理（簡單濾鏡）

#include <QApplication>
#include <QCamera>
#include <QCameraViewfinder>
#include <QCameraImageCapture>
#include <QAbstractVideoSurface>
#include <QVideoFrame>
#include <QImage>
#include <QPushButton>
#include <QVBoxLayout>
#include <QWidget>// 自定義視頻表面，用于處理視頻幀
class FrameProcessor : public QAbstractVideoSurface
{Q_OBJECT
public:explicit FrameProcessor(QObject *parent = nullptr) : QAbstractVideoSurface(parent) {}QList<QVideoFrame::PixelFormat> supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle) const override{Q_UNUSED(handleType);return QList<QVideoFrame::PixelFormat>()<< QVideoFrame::Format_RGB32<< QVideoFrame::Format_ARGB32<< QVideoFrame::Format_ARGB32_Premultiplied;}bool present(const QVideoFrame &frame) override{if (!frame.isValid())return false;QVideoFrame cloneFrame(frame);cloneFrame.map(QAbstractVideoBuffer::ReadOnly);// 獲取幀數據并轉換為圖像QImage image(cloneFrame.bits(), cloneFrame.width(), cloneFrame.height(), cloneFrame.bytesPerLine(), QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat()));// 應用簡單濾鏡（灰度化）QImage filteredImage = image.convertToFormat(QImage::Format_Grayscale8);cloneFrame.unmap();// 在這里可以處理過濾后的圖像（例如保存、顯示等）emit frameProcessed(filteredImage);return true;}signals:void frameProcessed(const QImage &image);
};int main(int argc, char *argv[])
{QApplication a(argc, argv);// 創建主窗口和布局QWidget window;QVBoxLayout *layout = new QVBoxLayout(&window);// 創建攝像頭QCamera *camera = new QCamera;// 創建取景器QCameraViewfinder *viewfinder = new QCameraViewfinder;camera->setViewfinder(viewfinder);// 創建幀處理器FrameProcessor *frameProcessor = new FrameProcessor;camera->setViewfinder(frameProcessor);// 添加控件到布局layout->addWidget(viewfinder);// 啟動攝像頭camera->start();// 顯示窗口window.show();return a.exec();
}#include "main.moc"