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前言

本项目实现了使用QT QML创建一个音频波形图进度条的功能。用户可以在界面上看到音频波形图，并且可以点击进度条上的位置进行定位，也可以拖动进度条来调整播放进度。可以让用户更方便地控制音频的播放进度，并且通过音频波形图可以直观地了解音频的节奏和节奏变化,为音频播放功能增添了更多的交互性和用户体验。

效果图

正文

本文使用QAudioDecoder进行音频解码，将解码数据计算后存储到数组中，解码完成后统一在QML中进行绘制。

关键代码：

#include "audiowaveform.h"
#include <QDebug>
#include <QUrl>
#include <QTime>AudioWaveform::AudioWaveform(QObject *parent): QObject(parent), m_decoder(new QAudioDecoder(this)), m_sampleCount(0)
{connect(m_decoder, &QAudioDecoder::bufferReady,this, &AudioWaveform::handleBufferReady);connect(m_decoder, &QAudioDecoder::finished,this, &AudioWaveform::handleFinished);connect(m_decoder, QOverload<QAudioDecoder::Error>::of(&QAudioDecoder::error),this, &AudioWaveform::handleError);
}AudioWaveform::~AudioWaveform()
{m_decoder->stop();
}QString AudioWaveform::source() const
{return m_source;
}void AudioWaveform::setSource(const QString &source)
{if (m_source != source) {m_source = source;emit sourceChanged();processAudioFile();}
}QVector<qreal> AudioWaveform::waveformData() const
{return m_waveformData;
}void AudioWaveform::processAudioFile()
{clearWaveformData();if (m_source.isEmpty()) {return;}m_decoder->setSourceFilename(m_source);QAudioFormat desiredFormat;desiredFormat.setChannelCount(1);desiredFormat.setCodec("audio/pcm");desiredFormat.setSampleRate(SAMPLE_RATE);desiredFormat.setSampleSize(16);desiredFormat.setSampleType(QAudioFormat::SignedInt);m_decoder->setAudioFormat(desiredFormat);m_decoder->start();qDebug() <<__FUNCTION__<< __LINE__<< QTime::currentTime().toString("hh:mm:ss.zzz");
}void AudioWaveform::handleBufferReady()
{QAudioBuffer buffer = m_decoder->read();if (!buffer.isValid())return;const qint16 *data = buffer.constData<qint16>();int sampleCount = buffer.sampleCount();// 计算这个缓冲区的最大振幅qreal maxAmplitude = 0;for (int i = 0; i < sampleCount; ++i) {qreal amplitude = qAbs(data[i]) / 32768.0; // 将16位整数转换为0-1范围maxAmplitude = qMax(maxAmplitude, amplitude);}m_waveformData.append(maxAmplitude);
}void AudioWaveform::handleFinished()
{qDebug() <<__FUNCTION__<< __LINE__ << QTime::currentTime().toString("hh:mm:ss.zzz");// 对波形数据进行重采样，使其具有固定的点数
//    if (m_waveformData.size() > WAVEFORM_POINTS) {
//        QVector<qreal> resampledData;
//        resampledData.reserve(WAVEFORM_POINTS);//        qreal step = m_waveformData.size() / static_cast<qreal>(WAVEFORM_POINTS);
//        for (int i = 0; i < WAVEFORM_POINTS; ++i) {
//            int index = static_cast<int>(i * step);
//            resampledData.append(m_waveformData.at(index));
//        }
//        m_waveformData = resampledData;
//    }emit waveformDataChanged();emit waveformProcessingFinished();
}void AudioWaveform::handleError(QAudioDecoder::Error error)
{QString errorMessage;switch (error) {case QAudioDecoder::NoError:return;case QAudioDecoder::ResourceError:errorMessage = "Resource error";break;case QAudioDecoder::FormatError:errorMessage = "Format error";break;case QAudioDecoder::AccessDeniedError:errorMessage = "Access denied error";break;case QAudioDecoder::ServiceMissingError:errorMessage = "Service missing error";break;default:errorMessage = "Unknown error";}emit this->error(errorMessage);
}void AudioWaveform::clearWaveformData()
{m_waveformData.clear();m_sampleCount = 0;emit waveformDataChanged();
}

波形绘制部分：

Canvas {id: waveformCanvasanchors.fill: parentanchors.margins: 2onPaint: {var ctx = getContext("2d");var width = waveformCanvas.width;var height = waveformCanvas.height;// 清除画布ctx.clearRect(0, 0, width, height);// 如果没有波形数据，直接返回if (!waveformModel || waveformModel.length === 0) return;// 设置波形样式ctx.strokeStyle = "#4a90e2";ctx.lineWidth = 2;// 计算每个数据点的宽度var pointWidth = width / waveformModel.length;// 绘制波形ctx.beginPath();waveformModel.forEach(function(amplitude, index) {var x = index * pointWidth;var centerY = height / 2;var waveHeight = amplitude * (height * 0.8);ctx.moveTo(x, centerY - waveHeight / 2);ctx.lineTo(x, centerY + waveHeight / 2);});ctx.stroke();// 绘制已播放部分的遮罩if (duration > 0) {var progress = currentPosition / duration;ctx.fillStyle = "rgba(74, 144, 226, 0.3)";ctx.fillRect(0, 0, width * progress, height);}}
}

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