Trying to capture QImage of video frame

Anjani

thanks for reply.I am new to Qt. but right now first I am making a project in my linux desktop system.Then I will cross compile it for target board.thats a later part. but now I want RGB frame image. What and where to change in code?please suggest me something

Anjani

In this program I am changing the test Index but still I am getting the same frame?

frame_capture.pro

#-------------------------------------------------
#Project created by QtCreator 2017-02-15T11:45:09
#-------------------------------------------------

QT += core gui multimedia multimediawidgets

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = frame_capture
TEMPLATE = app

SOURCES += main.cpp
frame_capture.cpp
v_player.cpp

HEADERS += frame_capture.h
v_player.h

frame_capture.h

#ifndef FRAME_CAPTURE_H
#define FRAME_CAPTURE_H

#include <QAbstractVideoSurface>
#include <QList>
#include <QDebug>
#include <QTime>

namespace Ui {
class frame_capture;
}

class frame_capture : public QAbstractVideoSurface
{
Q_OBJECT

public:
explicit frame_capture(QObject *parent = 0);
~frame_capture();
QListQVideoFrame::PixelFormat supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const;
bool present(const QVideoFrame &frame);
QTime timer;
int oldTime;

signals:
void frameAvailable(QImage frame);
void hereAreBytes(QByteArray*, int, int, int);
};

#endif // FRAME_CAPTURE_H

v_player.h

#ifndef V_PLAYER_H
#define V_PLAYER_H
#include "frame_capture.h"

#include <QObject>
#include <QMediaPlayer>
#include <QVideoWidget>
#include <QtWidgets>

class v_player : public QWidget
{
Q_OBJECT
public:
v_player(QWidget *parent = 0);
~v_player();
frame_capture *capture;

int counter = 0;
QString s;
QRect   rect;

private slots:
void handleBytes(QByteArray*, int, int, int);
void doClose();

private:
void paintEvent(QPaintEvent *event);

QMediaPlayer    mediaPlayer;
QPushButton     *closeButton;
bool closeIt = false;
QList<QByteArray*>  bytesList;
int numBytes;
int vpWidth, vpHeight;
QList<QImage*>  imageList;
quint8  myred, mygreen, myblue;

};
#endif // V_PLAYER_H

frame_capture.cpp

#include "frame_capture.h"
#include "v_player.h"

frame_capture::frame_capture(QObject *parent) : QAbstractVideoSurface(parent)
{
qDebug()<<"CONSTRUCTOR";
timer.start();
}

//---------- supportedPixelFormats ----------

QListQVideoFrame::PixelFormat frame_capture ::
supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
{
Q_UNUSED(handleType);
return QListQVideoFrame::PixelFormat()
<< QVideoFrame::Format_ARGB32
<< QVideoFrame::Format_ARGB32_Premultiplied
<< QVideoFrame::Format_RGB32
<< QVideoFrame::Format_RGB24
<< QVideoFrame::Format_RGB565
<< QVideoFrame::Format_RGB555
<< QVideoFrame::Format_ARGB8565_Premultiplied
<< QVideoFrame::Format_BGRA32
<< QVideoFrame::Format_BGRA32_Premultiplied
<< QVideoFrame::Format_BGR32
<< QVideoFrame::Format_BGR24
<< QVideoFrame::Format_BGR565
<< QVideoFrame::Format_BGR555
<< QVideoFrame::Format_BGRA5658_Premultiplied
<< QVideoFrame::Format_AYUV444
<< QVideoFrame::Format_AYUV444_Premultiplied
<< QVideoFrame::Format_YUV444
<< QVideoFrame::Format_YUV420P
<< QVideoFrame::Format_YV12
<< QVideoFrame::Format_UYVY
<< QVideoFrame::Format_YUYV
<< QVideoFrame::Format_NV12
<< QVideoFrame::Format_NV21
<< QVideoFrame::Format_IMC1
<< QVideoFrame::Format_IMC2
<< QVideoFrame::Format_IMC3
<< QVideoFrame::Format_IMC4
<< QVideoFrame::Format_Y8
<< QVideoFrame::Format_Y16
<< QVideoFrame::Format_Jpeg
<< QVideoFrame::Format_CameraRaw
<< QVideoFrame::Format_AdobeDng;
}

//---------- present ----------

bool frame_capture::present(const QVideoFrame &frame)
{
if (frame.isValid())
{
QVideoFrame cloneFrame(frame);
cloneFrame.map(QAbstractVideoBuffer::WriteOnly);
cloneFrame.pixelFormatFromImageFormat(QImage::Format_RGB32);

    int numBytes = cloneFrame.mappedBytes();
    QByteArray* bytesPtr = new QByteArray((const char*)(cloneFrame.bits()), numBytes);

    emit hereAreBytes(bytesPtr, numBytes, cloneFrame.width(), cloneFrame.height());
    cloneFrame.unmap();
    return true;

    qDebug()<<"\npixelFormat: "<<cloneFrame.pixelFormat();
    qDebug()<<"mappedBytes: "<<cloneFrame.mappedBytes();
    }
return false;

}

frame_capture::~frame_capture()
{
qDebug()<<"DESTRUCTOR";
}

main.cpp

#include <QApplication>
#include "v_player.cpp"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
v_player * player = new v_player();
player->setGeometry(300,300,480,300);
player->show();
int result = a.exec();
delete player;
return result;
}

v_player.cpp

#include "v_player.h"

v_player::v_player(QWidget *parent) : QWidget(parent) , mediaPlayer(0, QMediaPlayer::VideoSurface)
{

qDebug()<<"CONSTRUCTOR   VideoPlayer";
setAttribute(Qt::WA_QuitOnClose);
capture = new frame_capture(this);

QVideoWidget *videoWidget = new QVideoWidget;

videoWidget->setWindowTitle("Select a Video");

closeButton = new QPushButton("Close", this);
closeButton->setEnabled(true);

QBoxLayout *controlLayout = new QHBoxLayout;
controlLayout->setMargin(0);
controlLayout->addWidget(closeButton);
controlLayout->addWidget(videoWidget);
setLayout(controlLayout);
rect = QRect(002, 25, 150, 30);

//This line sends mediaPlayer video output to the grabber
mediaPlayer.setVideoOutput(capture);

//By uncommenting this line, the video is played in the VideoPlayer window.
//mediaPlayer.setVideoOutput(videoWidget);

//Playback at 1/10 speed to give time for frame capture
//mediaPlayer.setPlaybackRate(0.1);
mediaPlayer.setPlaybackRate(0.1);

QString fileName = "/home/einfochips/Downloads/Countdown_Timer_Background _10_Seconds.mpg";
if (!fileName.isEmpty())
{
    mediaPlayer.setMedia(QUrl::fromLocalFile(fileName));
    //playButton->setEnabled(true);
    mediaPlayer.play();
}
connect(capture, &frame_capture::hereAreBytes, this, &v_player::handleBytes);
connect(closeButton, SIGNAL(clicked()), this, SLOT(doClose()));
setWindowFlags(Qt::CustomizeWindowHint | Qt::WindowTitleHint);

}

//---------- ~VideoPlayer ----------

v_player::~v_player()
{
qDebug()<<"DESTRUCTOR VideoPlayer";

if ( ! bytesList.isEmpty())
{
    int testIndex = 150;
    QImage testImage = QImage((const uchar*)(bytesList.at(testIndex)), vpWidth, vpHeight, QImage::Format_RGB32, 0, 0);
    QString fileName = QFileDialog::getSaveFileName(this, "Save Image",
                                        "/home/einfochips/sitara/AM335x/Qt5.7.0/prog/frame_capture/build-frame_capture-Desktop_Qt_5_7_0_GCC_64bit-Debug/frame/testimage.png");
    testImage.save(fileName,"PNG");
    QTime  aDelay;
    aDelay.start();
    while (aDelay.elapsed() < 500)
    {
        int dummy = 0;
        dummy++;
    }
}
if ( ! bytesList.isEmpty())
{
    int num = bytesList.count();
    for (int i=0; i<num; i++)
        delete bytesList.at(i);
}

}

//---------- SLOT handleBytes ----------

void v_player::handleBytes(QByteArray* bytes, int nBytes, int w, int h)
{

bytesList.append(bytes);
numBytes = nBytes;
vpWidth = w;
vpHeight = h;

if (closeIt)
    QCoreApplication::quit();

counter++;
s.clear();
s = "Frame: " + QString::number(counter);
qDebug() << counter << endl;
update();

}

//---------- SLOT doClose ----------

void v_player::doClose()
{
qDebug()<<" doClose";
if (mediaPlayer.state() == QMediaPlayer::StoppedState)
QCoreApplication::quit();
if ((mediaPlayer.state() == QMediaPlayer::PlayingState) || (mediaPlayer.state() == QMediaPlayer::PausedState))
mediaPlayer.stop();
closeIt = true;
}

//---------- paintEvent ----------

void v_player::paintEvent(QPaintEvent * event)
{
QPainter painter(this);
painter.eraseRect(rect);
painter.drawText(rect, 0, s);
}

SGaist

Please, are you expecting us to analyse your complete application to find what index you may or may not modify ?

Anjani

no sir not really. The basic code is same as posted in this thread previously. This is just for the reference.You can directly suggest me which api or function will change the pixel formate of frame to RGB and allow me to save direct RGB only? or manually I need to add logic for conversion?
and the other thing I am not getting is why this gives me same frame? or I would say 1st frame only...

SGaist

It depends on the output you'll be using e.g. if OpenGL a shader will be used for that conversion.

Note that your grabber looks strange, you return all the types rather than just the one you would like to have and then you map the video frame as write only but you only read from it.

Anjani

Thank you for reply. I tried as you say. but didn't get any change in output.what I do now?
k if you can suggest me any thing which can change frame output(regardless of its formate) rather than being same all the time at any instance i capture a frame.Output is going to same and it is equal to first frame. for instance at least if i'll get different pictures for different frames than for formate i'll convert manually,just for now.

benlau

For converting YUV to RGB, Qt has a private API , qt_imageFromVideoFrame() , which could convert QVideoFrame to QImage in RGB format (I can't remember the exact RGB format to be converted) .

p.s It can't handle texture frame

You could try and see could it solve your problem first.

To enable the private API, you have to add this line in your .pro file

QT += multimedia-private

And include this header file

#include "private/qvideoframe_p.h"

Remarks: That is a private API. Use it as your own risk

Anjani

thank you for reply.I tried it but not working. I tried it after my clone frame syntax(in framegrabber.cpp file function present). Is that write position? I am new to Qt. I dont have much idea about it.

SGaist

Please be more precise. "Not working" doesn't say much. What are you getting ? A blank image ? A black image ? Funny colours ?

Anjani

@SGaist
ooh sorry for that. it still gives me .jpg image, where I want RGB data of image/frame.yet I am getting only the first frame all though I try to capture frame at any time.

SGaist

Aren't you getting a .png file ?

Anjani

yes i am getting .png but i want data in rgb format. because raw data format is only allowed on my frame buffer to display.

SGaist

You do realise that if you load your image again in a QImage, you'll get a RGB image ?

If you really want to save an RGB image then go for bitmap but beware, it's uncompressed.

Anjani

oh yes thank you. this will solve my problem partially. but what about new frame capture.? can you please help me out where I am lacking or what i am missing? why I am getting the same frame every time?If I'll get updated frame my task will be almost on final stage.please solve this.and again thank you.

SGaist

You always take the same image from the list, check that your counter increments properly and that you indeed update the list.

On a side note, you should pass const reference to QImage parameters. That will save useless copies.

Anjani

Thank you for reply and sorry for late response. Yes probably i am incrementing the counter properly. and sir I couldn't understand what you said about const reference to QImage parameter?

SGaist

Use: const QImage &image as parameter

Anjani

K let me try it