在做多媒体开发中我们经常需要做pcm（频谱）显示，这个例子专门使用libzplay库实现音频频谱动态显示，附加波动动画。看一下频谱的效果！

实现步骤：
首先我们需要去libzplay下载这个库，因为我使用了它来采集音频频谱数据。
然后配置pro文件

配置好了就开始写功能实现部分，直接上代码吧！

我写了一个专门读取音频数据的类：

AudioData.h

#ifndef AUDIODATA_H
#define AUDIODATA_H#include <QObject>
//#include <QAudioDecoder>
//#include <QAudioBuffer>
#include <QDebug>
//#include <QAudioDecoderControl>
#include <QFile>
#include "libzplay.h"
#include <QTimer>#include <QJsonDocument>
#include <QJsonArray>
#include <QJsonObject>
using namespace libZPlay;class AudioData : public QObject
{Q_OBJECT
public:explicit AudioData(QObject *parent = 0);Q_INVOKABLE void setSource(QString source);Q_INVOKABLE void playMusic();Q_INVOKABLE void stopMusic();Q_INVOKABLE void pauseMusic();Q_INVOKABLE void seekPosition(int ms);Q_PROPERTY(int amplitude READ amplitude NOTIFY amplitudeChanged)Q_PROPERTY(int position READ position NOTIFY positionChanged)Q_PROPERTY(bool isPlaying READ isPlaying NOTIFY isPlayingChanged)//music pcm dataQ_PROPERTY(QString pcmData READ pcmData NOTIFY pcmDataChanged)QString pcmData(){QJsonObject root;QJsonArray hn;for(int i =0;i<257;i++){hn.append (pnLeftAmplitude[i]);}root.insert ("data",hn);QJsonDocument doc;doc.setObject (root);return doc.toJson ();}signals:void amplitudeChanged();void positionChanged();void isPlayingChanged();void pcmDataChanged();public slots:void refreshDatas();
private:ZPlay *player;QTimer timer;int  pnHarmonicNumber[512];int  pnHarmonicFreq[257];int  pnLeftAmplitude[257];int  pnRightAmplitude[257];int  pnLeftPhase[257];int  pnRightPhase[257];int mposition=0;bool isMusicPlaying;int amplitude(){return pnRightAmplitude[171];}int position(){return mposition;}bool isPlaying(){return isMusicPlaying;}
};
#endif // AUDIODATA_H

AudioData.cpp

#include "audiodata.h"#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <QImage>AudioData::AudioData(QObject *parent) : QObject(parent)
{player=CreateZPlay();// set graph type to AREA, left channel on topplayer->SetFFTGraphParam(gpGraphType, gtAreaLeftOnTop);// set linear scaleplayer->SetFFTGraphParam(gpHorizontalScale, gsLinear);timer.setInterval(1);connect(&timer,SIGNAL(timeout()),this,SLOT(refreshDatas()));}
//music source
void AudioData::setSource(QString source){const char* msource=source.toLatin1().data();// open fileint result = player->OpenFile(msource, sfAutodetect);if(result == 0){// display error messageqDebug()<<"file open failed"<<player->GetError()<<endl;return;}}/*** @brief AudioData::playMusic*/
void AudioData::playMusic(){player->Play();timer.start();isMusicPlaying=true;isPlayingChanged();
}
/*** @brief AudioData::stopMusic*/
void AudioData::stopMusic(){player->Stop();timer.stop();isMusicPlaying=false;isPlayingChanged();
}
/*** @brief AudioData::pauseMusic*/
void AudioData::pauseMusic(){player->Pause();timer.stop();isMusicPlaying=false;isPlayingChanged();
}
/*** @brief AudioData::refreshDatas*/
void AudioData::refreshDatas(){// get song lengthTStreamInfo info;player->GetStreamInfo(&info);// check key pressif(kbhit()){int a = getch();if(a == 'p' || a == 'P')player->Pause();else if(a=='q'||a=='Q'){player->Stop();}}// get stream status to check if song is still playingTStreamStatus status;player->GetStatus(&status);if(status.fPlay == 0)return;// get current positionTStreamTime pos;player->GetPosition(&pos);this->mposition=pos.ms;positionChanged();int FFTPoints = player->GetFFTGraphParam(gpFFTPoints);player->GetFFTData(FFTPoints,fwTriangular,pnHarmonicNumber,pnHarmonicFreq,pnLeftAmplitude,pnRightAmplitude,pnLeftPhase,pnRightPhase);amplitudeChanged();pcmDataChanged();// draw FFT graph on desktop window//    player->DrawFFTGraphOnHWND(0, 0, 0, 300, 200);//    qDebug()<<pnLeftAmplitude[100]<<endl;}
/*** @brief AudioData::seekPosition* @param ms*/
void AudioData::seekPosition(int ms){TStreamTime time;time.ms=ms;player->Seek(tfMillisecond,&time,smFromBeginning);
}

main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <audiodata.h>
#include <QtQml>int main(int argc, char *argv[])
{QApplication app(argc, argv);QQmlApplicationEngine engine;AudioData ad;engine.rootContext()->setContextProperty("AudioData",&ad);engine.load(QUrl(QStringLiteral("qrc:/main.qml")));return app.exec();
}

main.qml

import QtQuick 2.5
import QtQuick.Controls 1.4
import QtQuick.Dialogs 1.2ApplicationWindow {visible: truewidth: 640height: 480title: qsTr("Hello World")property url soundUrl;
//    property var pcmDataM:new Array();property var pcmDatastr:AudioData.pcmDataListModel{id:dataModel}onPcmDatastrChanged: {try{if(dataModel.count===0)return;var jdata=JSON.parse(pcmDatastr).data;for(var a=0;a<jdata.length;a++){dataModel.setProperty(a,"pcmdata",jdata[a]);}}catch(e){console.log(e);}}id:mainwinComponent.onCompleted: {for(var a=0;a<257;a++){dataModel.append({"pcmdata":0});}}menuBar: MenuBar {Menu {title: qsTr("文件")MenuItem {text: qsTr("&打开MP3文件")onTriggered: {mdialog.open();}}}}FileDialog{id:mdialogfolder: shortcuts.homenameFilters: [ "Sound files (*.mp3)" ]onAccepted:{soundUrl=mdialog.fileUrl;AudioData.setSource(soundUrl.toString().substring(8,soundUrl.toString().length));AudioData.playMusic();}}Row{anchors.bottom: parent.bottomanchors.horizontalCenter: parent.horizontalCenterRepeater{model: dataModeldelegate: Rectangle{width: mainwin.width/dataModel.countheight: pcmdata*mainwin.height/255color:Qt.rgba(index/257,Math.abs(257-index)/257,Math.abs(257-index)/257,1)anchors.bottom: parent.bottom
//                radius: width/2
//                border.width:1
//                border.color:"#ffff12"Rectangle{width:parent.widthheight:1color:"#454545"}Behavior on height{PropertyAnimation{properties: "height"duration: 70}}}}}}