Qt 开源音视频框架模块之QtAV播放器实践

Qt 开源音视频框架模块QtAV播放器实践

1 摘要

QtAV是一个基于Qt的多媒体框架，旨在简化音视频播放和处理。它是一个跨平台的库，支持多种音视频格式，并提供了一个简单易用的API来集成音视频功能。QtAV的设计目标是为Qt应用程序提供强大的音视频处理能力，同时保持灵活性和可扩展性。可支持音频、视频播放，并提供了丰富的 API 和功能，让开发者能够轻松地处理多媒体数据。

2 QtAV的特点

•跨平台：支持Windows、Linux、macOS等多个操作系统。
•多媒体格式支持：支持多种音视频格式，包括常见的MP4、AVI、MKV、FLV、MP3、AAC等。
•高性能：基于FFmpeg，提供了高效的音视频解码和播放能力。
•简单易用的API：提供了直观的接口，方便开发者快速上手。
•集成Qt的特性：与Qt的信号和槽机制兼容，支持在Qt应用程序中使用。

3 简单播放器实践

3.1 环境配置

QtAv是基于ffmpeg开发的，因此我们需要下载相关依赖库。QtAV-depends-windows-x86+x64，下载完成后库目录结构如下

新建Qt项目QAVPlayer，在项目中添加QtAVWidgetsd库。

3.2 播放功能实现

•Qt实现简单的播放器功能，主要用到的函数：
•播放控制：play(), pause(), stop()等方法控制播放。
•音量调节：使用setVolume(int volume)方法设置音量。
•进度控制：使用seek(int position)方法跳转到特定时间。
•信号与槽：可以连接信号，例如播放结束、加载完成等事件，以便进行相应的处理。

初始化代码

 	QtAV::VideoOutput  *m_vo;
    QtAV::AVPlayer     *m_player;

 	QtAV::Widgets::registerRenderers();
    m_player = new QtAV::AVPlayer(this);
    m_vo = new QtAV::VideoOutput(this);
    m_player->setRenderer(m_vo);
    ui->verticalLayout->addWidget(m_vo->widget());
    connect(ui->playSlider, SIGNAL(sliderMoved(int)), SLOT(onSliderMoved(int)));
    connect(ui->playSlider, SIGNAL(sliderReleased()), SLOT(onSliderReleased()));
    connect(m_player, SIGNAL(positionChanged(qint64)), this, SLOT(onPositionChange(qint64)));
    connect(m_player, SIGNAL(notifyIntervalChanged()), SLOT(updateSliderUnit()));
    CommonUtils::loadStyleSheet(ui->playSlider, ":/QSS/QSS/VolumnSlider.css");
    connect(ui->volumnBtn, &VolumnButton::valueChanged, this, &MainWindow::onValueChanged);

打开文件播放功能代码

fileName= QFileDialog::getOpenFileName(this, tr("Open File"), "", tr("*.avi *.wmv *.mpg *.mpeg *.mov *.mp4 *.flv"));
           if (fileName.isEmpty())
               return;
m_player->seekBackward();
m_player->play(fileName);

暂停功能代码

	if (m_player->isPaused())
    {
        m_player->pause(false);
    }
    else
    {
        m_player->pause(true);
    }
    this->style()->unpolish(ui->abortBtn);
    this->style()->polish(ui->abortBtn);
    ui->abortBtn->update();

音量设置功能代码

void MainWindow::onValueChanged(int value)
{
    if (value == 0 && ui->volumnBtn->property("silence").toBool() == false)
    {
        ui->volumnBtn->setProperty("silence", true);
        ui->volumnBtn->setToolTip("静音");
    }
    else if (ui->volumnBtn->property("silence").toBool())
    {
        ui->volumnBtn->setProperty("silence", false);
        ui->volumnBtn->setToolTip("音量");
    }
    this->style()->unpolish(ui->volumnBtn);
    this->style()->polish(ui->volumnBtn);
    ui->volumnBtn->update();
    setVolume();
}

void MainWindow::setVolume()
{

     QtAV::AudioOutput *ao = m_player? m_player->audio() : 0;
    qreal v = qreal(ui->volumnBtn->volumnSlider()->value())*kVolumeInterval;
    if (ao) {
        if (qAbs(int(ao->volume() / kVolumeInterval) - ui->volumnBtn->volumnSlider()->value()) >= int(0.1 / kVolumeInterval)) {
            ao->setVolume(v);
        }
    }
}

音量滑竿功能代码

#include "volumnslider.h"
#include "commonutils.h"

#include <QStyleOption>
#include <QPainter>
#include <QLabel>
#include <QDebug>

VolumnSlider::VolumnSlider(QWidget *parent)
	: QSlider(parent)
{
    CommonUtils::loadStyleSheet(this, ":/QSS/QSS/VolumnSlider.css");
	setWindowFlags(Qt::FramelessWindowHint | Qt::SubWindow);
	setAttribute(Qt::WA_TranslucentBackground);

	m_label = new QLabel(nullptr);
	m_label->setStyleSheet("QLabel{color:rgb(179, 179, 179);background:rgb(69,69,69);}");
	m_label->setMargin(6);
	m_label->setFixedHeight(24);
	m_label->setWindowFlags(Qt::FramelessWindowHint | Qt::SubWindow);
	m_label->hide();
	this->setRange(0, 100);
	this->setValue(100);
}

VolumnSlider::~VolumnSlider()
{
	delete m_label;
}

void VolumnSlider::paintEvent(QPaintEvent *event)
{
	QStyleOption opt;
	opt.init(this);
	QPainter p(this);
	style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
	QSlider::paintEvent(event);
}

void VolumnSlider::showEvent(QShowEvent *event)
{
	setFocus();
	QSlider::showEvent(event);
}

void VolumnSlider::focusOutEvent(QFocusEvent *event)
{
	QPoint gloabPoint = this->mapToGlobal(QPoint(0, 0));
	QRect gloabRect(gloabPoint.x(), gloabPoint.y(), width(), height());
	if (!gloabRect.contains(QCursor::pos())){
		this->hide();
		m_label->hide();
	}
	else{
		this->setFocus();
	}
	QSlider::focusOutEvent(event);
}

void VolumnSlider::mouseMoveEvent(QMouseEvent *event)
{
	setLabelText();
	QSlider::mouseMoveEvent(event);
}

void VolumnSlider::mousePressEvent(QMouseEvent *event)
{
	setLabelText();
	m_label->show();
	QSlider::mousePressEvent(event);
}

void VolumnSlider::mouseReleaseEvent(QMouseEvent *event)
{
	m_label->hide();
	QSlider::mouseReleaseEvent(event);
}

void VolumnSlider::setLabelText()
{
	const QString&& value = QString::number(this->value());
	m_label->setFixedWidth(m_label->fontMetrics().width(value) + 12);
	m_label->setText(value);

	QPoint pos;;
	QPoint thePos = this->mapToGlobal(QPoint(0, 0));
	int posY = QCursor::pos().y();
	pos.setX(thePos.x() + 20);
	if (posY < thePos.y()){
		posY = thePos.y();
	}
	else if (posY > thePos.y() + this->height() - m_label->height()){
		posY = thePos.y() + this->height() - m_label->height();
	}
	pos.setY(posY);
	m_label->move(pos);
}

滑竿拖动快进功能核心代码

#include "playtimeslider.h"
//#include "head.h"

#include <QPainter>
#include <QVariant>
#include <QTime>
#include <QApplication>

const int pixwidth = 200;
const int pixheight = 116;

using namespace QtAV;
ImageWidget::ImageWidget(QWidget *parent)
{
    m_timestr = "00:00:00";
    m_extractor = new VideoFrameExtractor(this);
    setWindowFlags(Qt::FramelessWindowHint | Qt::SubWindow);
    setAttribute(Qt::WA_TranslucentBackground);
    hide();

    connect(m_extractor, SIGNAL(frameExtracted(QtAV::VideoFrame)), SLOT(displayFrame(QtAV::VideoFrame)));
    connect(m_extractor, SIGNAL(error(const QString &)), SLOT(displayNoFrame()));
    connect(m_extractor, SIGNAL(aborted(const QString &)), SLOT(displayNoFrame()));
}

void ImageWidget::displayFrame(const QtAV::VideoFrame &frame){
    if (!frame.isValid()) {
        displayNoFrame();
        return;
    }
    m_image = frame.toImage();
    update();
}

void ImageWidget::displayNoFrame()
{
    m_image = QImage();
    update();
}

void ImageWidget::seekVideoFrame(qint64 value)
{
    m_timestr = QTime(0, 0, 0).addMSecs(value).toString(QString::fromLatin1("HH:mm:ss"));
    m_extractor->setPosition(value);
    m_extractor->extract();
    update();
}

void ImageWidget::setPlayFile(const QString& file)
{
    m_extractor->setSource(file);
}

void ImageWidget::paintEvent(QPaintEvent *event)
{
    QWidget::paintEvent(event);
    QPainter painter(this);
    painter.setPen(Qt::NoPen);
    painter.setBrush(QColor("333333"));
    painter.drawRect(0, 0, this->width(), this->height() - 16);
    painter.setPen(Qt::white);
    painter.drawText(0, this->height() - 16, this->width(), 16, Qt::AlignCenter, m_timestr);
    painter.drawText(0, 0, this->width(), this->height() - 16, Qt::AlignCenter, "加载中...");
    if (!m_image.isNull()){
        painter.drawImage(QRect(0, 0, this->width(), this->height() - 16), m_image.scaled(this->width(), this->height() - 16, Qt::KeepAspectRatio, Qt::FastTransformation));
    }
}

PlayTimeSlider::PlayTimeSlider(QWidget *parent)
	: QSlider(parent)
{
	m_pixWidget = new ImageWidget(nullptr);
	m_pixWidget->setFixedSize(pixwidth, pixheight);
}

PlayTimeSlider::~PlayTimeSlider()
{
	delete m_pixWidget;
}

void PlayTimeSlider::stopPlayer()
{
	this->setValue(minimum());
}

void PlayTimeSlider::setPlayervalue(int value)
{
	if (!isSliderDown())
		setValue(value);
}

void PlayTimeSlider::showEvent(QShowEvent *event)
{
	setFocus();
	QSlider::showEvent(event);
}

void PlayTimeSlider::focusOutEvent(QFocusEvent *event)
{
	QPoint gloabPoint = this->mapToGlobal(QPoint(0, 0));
	QRect gloabRect(gloabPoint.x(), gloabPoint.y(), width(), height());
	if (!gloabRect.contains(QCursor::pos())){
		m_pixWidget->hide();
	}
	else{
		this->setFocus();
	}
	QSlider::focusOutEvent(event);
}

void PlayTimeSlider::mouseMoveEvent(QMouseEvent *event)
{
	updatePixWidgetPosition();
	QSlider::mouseMoveEvent(event);
}

void PlayTimeSlider::mousePressEvent(QMouseEvent *event)
{
	QSlider::mousePressEvent(event);
}

void PlayTimeSlider::mouseReleaseEvent(QMouseEvent *event)
{
	m_pixWidget->hide();
	QSlider::mouseReleaseEvent(event);
}

void PlayTimeSlider::setImageWidgetVisibe(bool visible)
{
	m_pixWidget->setVisible(visible);
}

void PlayTimeSlider::seekVideoFrame(qint64 value)
{
	m_pixWidget->seekVideoFrame(value);
}

void PlayTimeSlider::updatePixWidgetPosition()
{
	QPoint pos;
	QPoint thePos = this->mapToGlobal(QPoint(0, 0));
	int mouseX = QCursor::pos().x();
	int posX = mouseX - pixwidth / 2;
	pos.setY(thePos.y() - pixheight - 4);
	if (mouseX < thePos.x()){
		posX = thePos.x() - pixwidth / 2;
	}
	else if (mouseX > thePos.x() + this->width()){
		posX = thePos.x() + this->width() - pixwidth / 2;
	}
	pos.setX(posX);
	m_pixWidget->move(pos);
}

void PlayTimeSlider::setVideoFile(const QString& file)
{
	m_pixWidget->setPlayFile(file);
}

4 播放器效果

5 总结

本文介绍了Qt中开源音视频框架模块QtAV，通过使用该音视频播放库实现简单的播放器，了解该库的使用方法，可为后续音视频开发提供更丰富的功能，开发出更好用灵活音视频设计。后续则继续总结分享Qt应用开发中的其他应用，开发不易珍惜每一分原创和劳动成果，同时注意平时开发过程中的经验积累总结。