Qt中捕获视频流用两种方式:
一、用QCamera::setViewfinder(QAbstractVideoSurface *surface)
class MyVideoSurface : public QAbstractVideoSurface { QList<QVideoFrame::PixelFormat> supportedPixelFormats( QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle) const { Q_UNUSED(handleType); // 返回你将处理的格式 return QList<QVideoFrame::PixelFormat>() << QVideoFrame::Format_RGB32; } bool present(const QVideoFrame &frame) { Q_UNUSED(frame); // 处理捕获的帧 return true; } };
二、用QVideoProbe
camera = new QCamera; viewfinder = new QCameraViewfinder(); camera->setViewfinder(viewfinder); camera->setCaptureMode(QCamera::CaptureVideo); videoProbe = new QVideoProbe(this); if (videoProbe->setSource(camera)) { // Probing succeeded, videoProbe->isValid() should be true. connect(videoProbe, SIGNAL(videoFrameProbed(QVideoFrame)), this, SLOT(detectBarcodes(QVideoFrame))); } camera->start(); // Viewfinder frames should now also be emitted by // the video probe, even in still image capture mode. // Another alternative is to install the probe on a // QMediaRecorder connected to the camera to get the // recorded frames, if they are different from the // viewfinder frames.
windows实现了第一种方式,android实现了第二种方式。
windows支持格式为RGB24、RGB32;android支持格式为NV21
下面我对捕获和显示进行了封装:
CaptureVideoFrame.h
/* * 作者:康林(msn、email: [email protected]) * * 从摄像头(QCarmera)或者(Player)中捕获视频帧。 * 注意:android后景摄像头捕获的视频翻转-90度,前景摄像头翻转90度。 * 用法: * QCamera m_Camera; * m_Camera.setCaptureMode(QCamera::CaptureVideo); * CCaptureVideoFrame videoFrame; * videoFrame.setSource(&m_Camera); * 注册SLOT: * connect(&videoFrame, SIGNAL(CaptureFrame(const QVideoFrame&)), * SLOT(CaptureVideoFrame(const QVideoFrame&))); * 在SLOT 中 CaptureVideoFrame(const QVideoFrame&) 处理捕获到的视频帧。 * * 示例代码: * QList<QByteArray> device = QCamera::availableDevices(); * QList<QByteArray>::iterator it; * for(it = device.begin(); it != device.end(); it++) * { * qDebug("Camera:%s", qPrintable(QCamera::deviceDescription(*it))); * } * * QCamera camera(QCamera::availableDevices().at(1)); * camera.setCaptureMode(QCamera::CaptureVideo); * CFrmPlayer player; * CCaptureVideoFrame captureVideoFrame; * if(captureVideoFrame.setSource(&camera)) * { * qDebug("probe.setSource is ok"); * player.connect(&captureVideoFrame, SIGNAL(CaptureFrame(QVideoFrame)), * SLOT(present(QVideoFrame))); * } * * player.show(); * player.activateWindow(); * camera.start(); */ #ifndef CAPTUREVIDEOFRAME_H #define CAPTUREVIDEOFRAME_H #include <QAbstractVideoSurface> #include <QVideoProbe> #include <QCamera> class CCaptureVideoFrame : public QAbstractVideoSurface { Q_OBJECT public: explicit CCaptureVideoFrame(QObject *parent = 0); virtual QList<QVideoFrame::PixelFormat> supportedPixelFormats( QAbstractVideoBuffer::HandleType handleType = QAbstractVideoBuffer::NoHandle) const; bool setSource(QCamera *pCamera); signals: //视频帧捕获信号 void CaptureFrame(const QVideoFrame &frame); private slots: virtual bool present(const QVideoFrame &frame); private: QVideoProbe m_Probe;//android下,目前只能用probe捕获视频 }; #endif // CAPTUREVIDEOFRAME_H
CaptureVideoFrame.cpp
/** 作者:康林(msn、email: [email protected])*/ #include "CaptureVideoFrame.h" #include <QCamera> CCaptureVideoFrame::CCaptureVideoFrame(QObject *parent) : QAbstractVideoSurface(parent) { } QList<QVideoFrame::PixelFormat> CCaptureVideoFrame::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const { Q_UNUSED(handleType); QList<QVideoFrame::PixelFormat> lst; //lst.push_back(QVideoFrame::Format_YUYV);//Qt现在不支持此格式,因为Qt内部用了QImage来处理视频帧。 lst.push_back(QVideoFrame::Format_RGB32); lst.push_back(QVideoFrame::Format_BGR32); return lst; } //捕获视频帧。windows下格式是RGB32;android下是NV21 bool CCaptureVideoFrame::present(const QVideoFrame &frame) { qDebug("CCaptureVideoFrame::present format:%d", frame.pixelFormat()); emit CaptureFrame(frame); return true; } //根据不同的平台,设置捕获方式 bool CCaptureVideoFrame::setSource(QCamera *pCamera) { bool ret = true; #ifdef ANDROID //android下,目前只能用probe捕获视频 ret = m_Probe.setSource(pCamera); if(ret) { connect(&m_Probe, SIGNAL(videoFrameProbed(QVideoFrame)), SLOT(present(QVideoFrame))); } #else //windows下,只能用下面方式捕获视频 pCamera->setViewfinder(this); #endif return ret; }
注意:android使用时需要定义 ANDROID 宏
QT对摄像头的支持存在的一些问题:
QT得到到捕获帧相关的参数
QT 在windows、linux下捕获视频只有5帧/秒左右,在我的电脑上用时 240ms 左右。在Android手机上可达到15帧/s(60ms左右)。
QT 在 windows、linux下多个摄像头切换正常,但在 android 手机上,前后摄像头不能切换。代码如下:
void CFrmVideo::on_cmbCamera_currentIndexChanged(int index) { LOG_MODEL_DEBUG("Video", "CFrmVideo::on_cmbCamera_currentIndexChanged"); m_CameraPostition = QCamera::availableDevices().at(index); OpenCamera(); LOG_MODEL_DEBUG("Video", "CFrmVideo::on_cmbCamera_currentIndexChanged end"); } int CFrmVideo::OpenCamera() { if(!m_pCall) { LOG_MODEL_ERROR("Video", "CFrmVideo::OpenCamera m_pCall is null"); return -1; } if(m_pCamera) { CloseCamera(); } m_pCamera = new QCamera(m_CameraPostition); if(!m_pCamera) { LOG_MODEL_WARNING("Video", "Open carmera fail"); return -1; } m_pCamera->setCaptureMode(QCamera::CaptureVideo); m_CaptureVideoFrame.setSource(m_pCamera); //m_pCamera->load(); m_pCamera->start(); return 0; } int CFrmVideo::CloseCamera() { if(m_pCamera) { m_pCamera->stop(); //m_pCamera->unload(); delete m_pCamera; m_pCamera = NULL; } return 0; }