QT开发技术【ffmpeg + QAudioOutput】音乐播放器 完善

一、完善上章的功能，形成一个小工具

QT开发技术【ffmpeg + QAudioOutput】音乐播放器

二、增加歌曲保存类

#include "../Include/MusicListManager.h"
#include "QtGui/Include/Conversion.h"
#include <QFile>
#include <QXmlStreamReader>
#include <QXmlStreamWriter>
#include <QDebug>

CMusicListManager::CMusicListManager()
{

}

CMusicListManager::~CMusicListManager()
{

}

bool CMusicListManager::AddMusic(const std::string& strMusicFilePath)
{
	for (auto& itr : m_vecMusicList)
	{
		if (itr.strMusicPath == strMusicFilePath)
		{
			return false;
		}
	}

	stMusicInfo stMusicInfo;
	stMusicInfo.strMusicName = strMusicFilePath.substr(strMusicFilePath.find_last_of("\\/") + 1).substr(0, strMusicFilePath.find_last_of("."));
	stMusicInfo.strMusicPath = strMusicFilePath;
	m_vecMusicList.push_back(stMusicInfo);
	return true;
}

void CMusicListManager::RemoveMusic(const std::string& strMusicFilePath)
{
	for (auto itr = m_vecMusicList.begin(); itr!= m_vecMusicList.end(); ++itr)
	{
		if (itr->strMusicPath == strMusicFilePath)
		{
			m_vecMusicList.erase(itr);
			return;
		}
	}
}


stMusicInfo CMusicListManager::GetMusicInfoByIndex(int nIndex) const
{
	if (nIndex < 0)
	{
		nIndex = m_vecMusicList.size() - 1;
	}
	else if (nIndex >= (int)m_vecMusicList.size())
	{
		nIndex = 0;
	}
	return m_vecMusicList[nIndex];
}

void CMusicListManager::Clear()
{
	m_vecMusicList.clear();
}

std::vector<stMusicInfo> CMusicListManager::GetMusicList() const
{
	return m_vecMusicList;
}

void CMusicListManager::Load(const std::string& strSaveFilePath)
{
	m_strSaveFilePath = strSaveFilePath;
	QFile file(TransString2Unicode(strSaveFilePath));
	if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) 
	{
		qDebug() << TransString2Unicode("无法打开文件:" +strSaveFilePath);
		return;
	}
	m_vecMusicList.clear();

	QXmlStreamReader xmlReader(&file);
	while (!xmlReader.atEnd() && !xmlReader.hasError())
	{
		QXmlStreamReader::TokenType token = xmlReader.readNext();
		if (token == QXmlStreamReader::StartElement) 
		{
			if (xmlReader.name() == "Music")
			{
				QXmlStreamAttributes attributes = xmlReader.attributes();
				if (attributes.hasAttribute("name") && attributes.hasAttribute("path")) {
					QString name = attributes.value("name").toString();
					QString path = attributes.value("path").toString();
					stMusicInfo stMusicInfo;
					stMusicInfo.strMusicName = TransUnicode2String(name);
					stMusicInfo.strMusicPath = TransUnicode2String(path);
					m_vecMusicList.push_back(stMusicInfo);
				}
			}
		}
	}
}


void CMusicListManager::Save()
{
	QFile file(TransString2Unicode(m_strSaveFilePath));
	if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
	{
		qDebug() <<  TransString2Unicode("无法打开文件进行写入:" + m_strSaveFilePath);
		return;
	}

	QXmlStreamWriter xmlWriter(&file);
	xmlWriter.setAutoFormatting(true); // 自动格式化 XML 内容
	xmlWriter.writeStartDocument();
	xmlWriter.writeStartElement("MusicList");
	for (auto& itr : m_vecMusicList)
	{
		xmlWriter.writeStartElement("Music");
		xmlWriter.writeAttribute("name", TransString2Unicode(itr.strMusicName));
		xmlWriter.writeAttribute("path", TransString2Unicode(itr.strMusicPath));
		xmlWriter.writeEndElement(); // 结束 Music 元素
	}
	xmlWriter.writeEndElement(); // 结束 MusicList 元素
	xmlWriter.writeEndDocument();

	file.close();
}

三、界面一些按钮控制实现

#include "../Include/EMusicMainWindow.h"
#include "ui_EMusicMainWindow.h"
#include "QtGui/Include/Conversion.h"
#include <QFileDialog>
#include <QThread>
#include <QDebug>

CEMusicMainWindow::CEMusicMainWindow(QWidget* parent)
    : QMainWindow(parent)
   , ui(std::make_unique<Ui::CEMusicMainWindow>())
{
    ui->setupUi(this);
    InitUI();
}

CEMusicMainWindow::~CEMusicMainWindow()
{
    m_AudioPlayer.Stop();
    m_AudioPlayer.Quit();
    m_pMusicLocalListManager->Save();
}

void CEMusicMainWindow::InitUI()
{
    m_bIsPlaying = false;
    m_bSeeking = false;
    m_eCycleType = E_CYCLE_ALL;
    m_pMusicLocalListManager = std::make_unique<CMusicListManager>();
    std::string strMusicListPath = TransUnicode2String(QCoreApplication::applicationDirPath()) + "/MusicList.xml";
    m_pMusicLocalListManager->Load(strMusicListPath);
    std::vector<stMusicInfo> vecMusicList = m_pMusicLocalListManager->GetMusicList();
    for (auto musicInfo : vecMusicList)
    {
        QListWidgetItem* item = new QListWidgetItem(QIcon(":/Music_File.png"), TransString2Unicode(musicInfo.strMusicName));
        ui->listWidget_All->addItem(item);
    }
    connect(&m_AudioPlayer, &CAudioPlayer::SigDuration, this, &CEMusicMainWindow::SlotUpdateLyricsAndTime);
    connect(&m_AudioPlayer, &CAudioPlayer::SigSeekOk, this, &CEMusicMainWindow::SlotSeekOk);
}

void CEMusicMainWindow::on_pushButton_StopOrPlay_clicked()
{
    if (m_strMusicFilePath.isEmpty())
    {
        return;
    }

    if (m_bIsPlaying)
    {
        m_bIsPlaying = false;
        m_AudioPlayer.Pause();
        ui->pushButton_StopOrPlay->setStyleSheet("image: url(:/Play.png);");
    }
    else
    {
        m_bIsPlaying = true;
        m_bSeeking = false;
        ui->pushButton_StopOrPlay->setStyleSheet("image: url(:/Stop.png);");
        if (m_strOldMusicFilePath.isEmpty())
        {
            m_strOldMusicFilePath = m_strMusicFilePath;
            m_LyricsReader.LoadLrcFile(m_strMusicFilePath.split('.').first() + ".lrc");
            m_AudioPlayer.Play(TransUnicode2String(m_strMusicFilePath));
        }
        else if (m_strMusicFilePath != m_strOldMusicFilePath)
        {
            m_strOldMusicFilePath = m_strMusicFilePath;
            m_LyricsReader.LoadLrcFile(m_strMusicFilePath.split('.').first() + ".lrc");
            m_AudioPlayer.Play(TransUnicode2String(m_strMusicFilePath));
        }
        else if(m_AudioPlayer.GetControlType() == CAudioPlayer::E_CONTROL_PAUSE)
        {
            m_AudioPlayer.Resume();
        }
        else 
        {
            m_strOldMusicFilePath = m_strMusicFilePath;
            m_AudioPlayer.Play(TransUnicode2String(m_strMusicFilePath));
        }
    }
}

void CEMusicMainWindow::SlotUpdateLyricsAndTime(int nCurrentTime, int nDestTime)
{
    std::string strLyrics = m_LyricsReader.GetCurrentLyrics(nCurrentTime);
    ui->label_Words->setText(TransString2Unicode(strLyrics));

    if (nCurrentTime == nDestTime && nCurrentTime != 0)
    {
        if (m_eCycleType == E_CYCLE_SINGLE)
        {
            m_AudioPlayer.Play(TransUnicode2String(m_strMusicFilePath));
        }
        else
        {
            on_pushButton_Next_clicked();
        }
    }

    static int currentMs1 = -1, destMs1 = -1;

    if (currentMs1 == nCurrentTime && destMs1 == nDestTime)
    {
        return;
    }

    currentMs1 = nCurrentTime;
    destMs1 = nDestTime;

    //qDebug() << "onDuration:" << nCurrentTime << nDestTime << m_bSeeking;


    QString currentTime = QString("%1:%2:%3").arg(currentMs1 / 360000 % 60, 2, 10, QChar('0')).arg(currentMs1 / 6000 % 60, 2, 10, QChar('0')).arg(currentMs1 / 1000 % 60, 2, 10, QChar('0'));

    QString destTime = QString("%1:%2:%3").arg(destMs1 / 360000 % 60, 2, 10, QChar('0')).arg(destMs1 / 6000 % 60, 2, 10, QChar('0')).arg(destMs1 / 1000 % 60, 2, 10, QChar('0'));


    ui->label_Process->setText(currentTime + "/" + destTime);



    if (!m_bSeeking) //未滑动
    {
        ui->slider_Seek->setMaximum(nDestTime);
        ui->slider_Seek->setValue(nCurrentTime);
    } 
}

void CEMusicMainWindow::SlotSeekOk()
{
    m_bSeeking = false;
}

void CEMusicMainWindow::on_slider_Seek_sliderPressed()
{
    m_bSeeking = true;
}

void CEMusicMainWindow::on_slider_Seek_sliderReleased()
{
    m_AudioPlayer.Seek(ui->slider_Seek->value());
}

void CEMusicMainWindow::on_listWidget_All_itemDoubleClicked(QListWidgetItem* item)
{
    int nIndex = ui->listWidget_All->row(item);
    if (nIndex < 0)
    {
        return;
    }

    stMusicInfo musicInfo = m_pMusicLocalListManager->GetMusicInfoByIndex(nIndex);
    if (musicInfo.strMusicPath.empty())
    {
        return;
    }
    m_strMusicFilePath = TransString2Unicode(musicInfo.strMusicPath);
    m_bIsPlaying = false;
    on_pushButton_StopOrPlay_clicked();
}

void CEMusicMainWindow::on_pushButton_CycleOrSingle_clicked()
{
    if (m_eCycleType == E_CYCLE_ALL)
    {
        m_eCycleType = E_CYCLE_SINGLE;
        ui->pushButton_CycleOrSingle->setStyleSheet("image: url(:/SingleCycle.png);");
    }
    else
    {
        m_eCycleType = E_CYCLE_ALL;
        ui->pushButton_CycleOrSingle->setStyleSheet("image: url(:/Cycle.png);");
    }
}

void CEMusicMainWindow::on_pushButton_Prev_clicked()
{
    int nIndex = ui->listWidget_All->currentRow();
    if (nIndex < 0)
    {
        return;
    }
    stMusicInfo musicInfo = m_pMusicLocalListManager->GetMusicInfoByIndex(nIndex - 1);
    if (musicInfo.strMusicPath.empty())
    {
        return;
    }

    if (nIndex - 1 < 0)
    {
        ui->listWidget_All->setCurrentRow(ui->listWidget_All->count() - 1);
    }
    else
    {
        ui->listWidget_All->setCurrentRow(nIndex - 1);
    }

    m_strMusicFilePath = TransString2Unicode(musicInfo.strMusicPath);
    m_bIsPlaying = false;
    on_pushButton_StopOrPlay_clicked();
}

void CEMusicMainWindow::on_pushButton_Next_clicked()
{
    int nIndex = ui->listWidget_All->currentRow();
    if (nIndex < 0)
    {
        return;
    }

    stMusicInfo musicInfo = m_pMusicLocalListManager->GetMusicInfoByIndex(nIndex + 1);
    if (musicInfo.strMusicPath.empty())
    {
        return;
    }

    if (nIndex + 1 >= ui->listWidget_All->count())
    {
        ui->listWidget_All->setCurrentRow(0);
    }
    else
    {
        ui->listWidget_All->setCurrentRow(nIndex + 1);
    }

    m_strMusicFilePath = TransString2Unicode(musicInfo.strMusicPath);
    m_bIsPlaying = false;
    on_pushButton_StopOrPlay_clicked();
}

void CEMusicMainWindow::on_pushButton_DeleteAll_clicked()
{
    ui->listWidget_All->clear();
    m_pMusicLocalListManager->Clear();
}


void CEMusicMainWindow::on_pushButton_Select_clicked()
{
    QDir dir = QFileDialog::getExistingDirectory(this, TransString2Unicode("选择音乐文件夹"), QDir::currentPath());
    if (dir.exists())
    {
        QStringList filters;
        filters << "*.mp3";
        QStringList files = dir.entryList(filters, QDir::Files);
        for (auto file : files)
        {
            std::string strFilePath = TransUnicode2String(dir.absoluteFilePath(file));
            if (m_pMusicLocalListManager->AddMusic(strFilePath))
            {
                QListWidgetItem* item = new QListWidgetItem(QIcon(":/Music_File.png"), file.split('.').first());
                ui->listWidget_All->addItem(item);
            }
        }
    }
}

四、总结

成功利用 Qt 和 FFmpeg 实现了一个简单的音乐播放器，掌握了音频解码、播放以及用户界面设计等相关技术。

音频解码技术详解

音频解码是将压缩的数字音频数据还原为原始波形信号的过程，是现代数字音频处理的核心环节。

音频解码的基本流程

数据输入：接收压缩的音频数据流（如MP3、AAC、FLAC等格式文件）

格式解析：识别音频文件的封装格式和编码标准

解码运算：根据特定算法进行解压缩运算，常见方法包括：

频率域变换（如MP3使用的MDCT变换）

预测编码解算

熵解码（Huffman编码等）

后处理：包括重采样、抖动处理、声道映射等

输出PCM：最终产生脉冲编码调制(PCM)信号，供数模转换器使用

主要音频编码标准

有损压缩

MP3(MPEG-1 Audio Layer III)：使用心理声学模型，去除人耳不敏感的频段

AAC(Advanced Audio Coding)：改进的MP3算法，效率提高约30%

Opus：低延迟编码，适合实时通信

无损压缩

FLAC(Free Lossless Audio Codec)：保持原始音质，压缩率约50%

ALAC(Apple Lossless)：苹果设备常用无损格式

应用场景

消费电子：智能手机、数字音乐播放器

广播系统：数字广播、网络流媒体

专业音频：录音棚、现场扩声系统

车载音响：支持多格式解码的高保真系统

关键技术指标

解码延迟

资源占用率

格式兼容性

音质还原度

错误恢复能力

现代音频解码器通常集成DSP处理功能，可同时实现均衡、混响等效果处理。随着AI技术的发展，基于神经网络的音频解码算法正在逐步商业化。