QProcess in a loop, works but....

[Joelito]

This my code:

class MyQTForm : public QMainWindow {
private:
    Q_OBJECT
    QProcess *process;
//...

class MyQTForm : public QMainWindow {
private:
    Q_OBJECT
    QProcess *process;
//...

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Now the part I want to process:

void MyQTForm::cb_process_dir(const QString& _in, const QString& _out) {
    QDir in_dir (_in);
    QStringList filters;
    filters << "*.mp3" << "*.flv" << "*.mp4";
    QStringList dir_list = in_dir.entryList (filters);
    int index = 0;
    int total = dir_list.size();
    for (; index < total; index++) {
        QString file_in = _in + QString("/") + dir_list[index];
        QFileInfo fi(file_in);
        QString file_out = _out + QString("/") + fi.baseName() + QString(".mp3");
        cb_process (file_in, file_out); // a lot of files to process
    }
}
 
void MyQTForm::cb_process (const QString& file_in, const QString& file_out) {
    QString cmd;
    QTextStream(&cmd) << "ffmpeg -i \"" << file_in << "\" -f mp3 -ab 128k \"" << file_out << "\"";
    process = new QProcess(this);
    process->setStandardOutputFile(tr("/dev/null"));
    connect(process, SIGNAL(started()),this, SLOT(onProcessStarted ()));
    connect(process, SIGNAL(finished(int, QProcess::ExitStatus)),this, SLOT(onProcessEnded ()));
    connect(process, SIGNAL(finished(int,QProcess::ExitStatus)), process, SLOT(deleteLater()) );
    process->start(cmd);
}
 
void MyQTForm::onProcessStarted() {
    activo = true;
    menuBar()->setEnabled(!activo);
    statusBar()->showMessage(tr("Convirtiendo..."));
}
 
void MyQTForm::onProcessEnded() {
    activo = false;
    menuBar()->setEnabled(!activo);
    if (check1->isChecked()) {
        //QFile::remove (_out_file_tmp);
    }
    statusBar()->showMessage(tr("Hecho"));
}

void MyQTForm::cb_process_dir(const QString& _in, const QString& _out) {
    QDir in_dir (_in);
    QStringList filters;
    filters << "*.mp3" << "*.flv" << "*.mp4";
    QStringList dir_list = in_dir.entryList (filters);
    int index = 0;
    int total = dir_list.size();
    for (; index < total; index++) {
        QString file_in = _in + QString("/") + dir_list[index];
        QFileInfo fi(file_in);
        QString file_out = _out + QString("/") + fi.baseName() + QString(".mp3");
        cb_process (file_in, file_out); // a lot of files to process
    }
}

void MyQTForm::cb_process (const QString& file_in, const QString& file_out) {
    QString cmd;
    QTextStream(&cmd) << "ffmpeg -i \"" << file_in << "\" -f mp3 -ab 128k \"" << file_out << "\"";
    process = new QProcess(this);
    process->setStandardOutputFile(tr("/dev/null"));
    connect(process, SIGNAL(started()),this, SLOT(onProcessStarted ()));
    connect(process, SIGNAL(finished(int, QProcess::ExitStatus)),this, SLOT(onProcessEnded ()));
    connect(process, SIGNAL(finished(int,QProcess::ExitStatus)), process, SLOT(deleteLater()) );
    process->start(cmd);
}

void MyQTForm::onProcessStarted() {
    activo = true;
    menuBar()->setEnabled(!activo);
    statusBar()->showMessage(tr("Convirtiendo..."));
}

void MyQTForm::onProcessEnded() {
    activo = false;
    menuBar()->setEnabled(!activo);
    if (check1->isChecked()) {
        //QFile::remove (_out_file_tmp);
    }
    statusBar()->showMessage(tr("Hecho"));
}

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This are the results:
1.- ffmpeg is launch as many times as many files are passed to cb_process, bad idea if we found a lot :\
2.- at some point I get: QProcess: Destroyed while process is still running.

My idea is that " process->start(cmd);" sould wait untill the current ffmpeg operation is done, so it can continue the loop...any help, please?

[Santosh Reddy]

Then avoid the for loop and start the next process in the slot "onProcessEnded()"

[Joelito]

How should I avoid the for loop if I want to convert files in "dir_list" from the method "cb_process_dir"?

[myta212]

Hi,
You can use void QProcess::finished ( int exitCode, QProcess::ExitStatus exitStatus ) [signal] to running QProcess in a loop. This signal will executed after the current QProcess active finished. This is my simple QProcess::finished function contents :

//this function will executed at the end of every process
void Qt_Loop_QProcess::finishedProcess ( int exitCode, QProcess::ExitStatus exitStatus )
{
	ui.textReport->append("complete"); //finishid process command
 
    if(idxProcess<nExtension) //run qprocess again until all extension finished
    {
    	ui.listCommand->setCurrentRow(idxProcess);
 
    	/* create QProcess object */
    	proc= new QProcess();
    	QString strCommand = setCommand(listExtension.at(idxProcess));
    	proc->start("/bin/bash", QStringList() << "-c" << strCommand);
 
    	/* show output */
    	connect(proc, SIGNAL(readyReadStandardOutput()),this, SLOT(rightMessage()) );
    	connect(proc, SIGNAL(readyReadStandardError()), this, SLOT(wrongMessage()) );
    	connect(proc, SIGNAL(finished(int, QProcess::ExitStatus)),
    			this, SLOT(finishedProcess(int, QProcess::ExitStatus)) );
 
    	idxProcess++;
    }
}

//this function will executed at the end of every process
void Qt_Loop_QProcess::finishedProcess ( int exitCode, QProcess::ExitStatus exitStatus )
{
	ui.textReport->append("complete"); //finishid process command

    if(idxProcess<nExtension) //run qprocess again until all extension finished
    {
    	ui.listCommand->setCurrentRow(idxProcess);

    	/* create QProcess object */
    	proc= new QProcess();
    	QString strCommand = setCommand(listExtension.at(idxProcess));
    	proc->start("/bin/bash", QStringList() << "-c" << strCommand);

    	/* show output */
    	connect(proc, SIGNAL(readyReadStandardOutput()),this, SLOT(rightMessage()) );
    	connect(proc, SIGNAL(readyReadStandardError()), this, SLOT(wrongMessage()) );
    	connect(proc, SIGNAL(finished(int, QProcess::ExitStatus)),
    			this, SLOT(finishedProcess(int, QProcess::ExitStatus)) );

    	idxProcess++;
    }
}

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I get this tutorial at here http://toto-share.com/2011/11/qt-qprocess-in-a-loop. So, if you interest, you can download the complete source code at that location

Best regards,

Myta