@Ajith_P_V , maybe, you need not RGB, but BGR model. I didn't work with graphics in qt, but in OpenCV all work was gone in BGR.

Thank all for your replay,
I solve my problem by using Phonon: :video player

Steps:-

i. Add Phonon::Video Player in ui file. I rename its programing name as "Video Player"
ii. Add one button in that ui file and go to that button slot and adding following code in it:-
// For getting system date and time for video name
time_t now = time(0);
struct tm tstruct;
char buf[80];
tstruct = *localtime(&now);

strftime(buf, sizeof(buf), "%d_%m_%y_%H_%M", &tstruct); qDebug() << "Date and Time: "<<buf;

// For getting static path where video will be stored
QString a = "/home/Working_QT/BackupErrorWorking/DeviceTestVersion1/video/";
a.append(buf);
a.append(".avi");
qDebug() << "a: "<<a;

// For giving comlete command as it is accepted as a QString and converted into char(Because konsole command is accepted only char it shows error so we convert it)
QString command = "ffmpeg -f video4linux2 -i /dev/video0 -vcodec mpeg4 -b 500k -r 25 -t 00:01:30 ";
command.append(a);
qDebug() << "Command: "<<command;
char x[200];
strcpy( x, command.toStdString().c_str());

// Commaand to sysytem
system(x);
qDebug() << "Command given to system to capture video and name it according to that particular date and time: "<<x;

// For playing video through Phonon VideoPlayer
qDebug("Before video recording display");
ui->VideoPlayer->play(Phonon::MediaSource(a));
qDebug("After video recording display");

iii. Included #include <time.h> // Required for giving video file name according to date and time
and #include <qdebug.h>
iv. Make changes in .pro file

QT += phonon