problem with file format



  • Hi
    I want to save mp4 format to windows directory ( like c:/test/testnewfolder )
    So i get file and true but my file is code and don't mp4 and i don't see any film and player get error.
    I used QByteArray , QFile , QDataStream .
    What i do?
    Thnaks


  • Qt Champions 2016

    Hi
    How do you convert it to mp4 format?
    Do you load a mp4 file and then save it some other place?

    Please show code for what you do.



  • @mrjj Thanks

     QByteArray ba = reply->readAll();
        QString filename="C:/Users/armin/Desktop/New folder.mp4";
        QFile file(filename);
        file.open(QIODevice::WriteOnly);
        QDataStream out(&file);
        out << ba;
    

  • Qt Champions 2016

    @Armin
    Hi That will save what ever you get from reply->readAll();
    directly to a file.
    So unless it WAS mp4 format to begin with, all you did was to save the
    bytes directly from the readAll()

    So Question 1 is
    Is the file you are READING already mp4 ?
    Are you are downloading a MP4 file and try to save it later?



  • @mrjj Thanks
    I downloaded file and save in directory of windows , but don't run :(



  • the problem is probably in reply->readAll(); when do you call this function?



  • @VRonin Thanks
    In first.
    You see my code in above.


  • Qt Champions 2016

    @Armin
    Hi
    Did you try to download the file normally and check that it can play ?
    Also did you compare the size of the file when u saved it ?
    How many bytes compared to the orginal file?



  • @mrjj Thanks
    when i download with download manager everything is ok,
    but when i download it my app, file have problems.



  • QByteArray ba = reply->readAll();
    QString filename="C:/Users/armin/Desktop/New folder.mp4";
    QFile file(filename);
    file.open(QIODevice::WriteOnly);
    QDataStream out(&file);
    out << ba;

    I do not think the problem is here but rather in where you call this from. Is this connected to a QNetworkReply?


  • Moderators

    @Armin said in problem with file format:

    QByteArray ba = reply->readAll();
    QString filename="C:/Users/armin/Desktop/New folder.mp4";
    QFile file(filename);
    file.open(QIODevice::WriteOnly);
    QDataStream out(&file);
    out << ba;

    readAll() does not necessarily return the whole file at once!
    You need to call readAll() each time you get data over network (see http://doc.qt.io/qt-5/qiodevice.html#readyRead) and APPEND that data to the file.



  • @VRonin
    i don't have any problem with saving file,
    file will be saved correctly.
    size is also correct , i just don't know why file will not execute.


  • Moderators

    @Armin If the file is not working then it is broken (even if the size is same). Did you try to compare both files (binary diff)? For example you can calculate a hash for each file and if those hashes are different then file content is not the same.


  • Moderators

    @Armin Another idea: do you close the file after writing? If not and your app is still running then maybe the video-player cannot play it because the file is open in your application.



  • @jsulm

    {
        QByteArray ba = reply->readAll();
        QString filename="C:/Users/armin/Desktop/New folder.mp4";
        QFile file(filename);
        file.open(QIODevice::ReadWrite);
        QDataStream out(&file);
        out << ba;
        file.close();
    }
    

    I accomplished. is it true?


  • Moderators

    @Armin file.close() is not needed as QFile instance is a local variable and closes the file automatically when it goes out of scope. But you can try.
    Did you try to calculate hashes?
    On Linux it would be just

    md5sum file
    


  • file.open(QIODevice::ReadWrite);

    try with file.open(QIODevice::WriteOnly);

    You still haven't answered what reply is and when this block of code gets called.

    do you have something like connect(reply,SIGNAL(readyRead()), /*...*/ ?



  • @VRonin Thanks

    void MainWindow::on_pushButton_clicked()
    {
        QNetworkAccessManager *manager = new QNetworkAccessManager(this);
        connect(manager , SIGNAL(finished(QNetworkReply*)) , this , SLOT(replyFinished(QNetworkReply*)));
        manager->get(QNetworkRequest(QUrl(ui->textEdit->toPlainText())));
    
    }
    


  • @jsulm Thanks
    Hashes? I don't know about that


  • Moderators

    @Armin Well, you can learn. I provided an example how to calculate md5 hash for a file.



  • QNetworkAccessManager should usually not be built and destroyed every time, you are also leaking memory.

    • add QNetworkAccessManager* m_manager; as a private member in MainWindow
    • in MainWindow constructor add
    m_manager=new QNetworkAccessManager(this);
    connect(manager , SIGNAL(finished(QNetworkReply*)) , this , SLOT(replyFinished(QNetworkReply*)));
    
    • change MainWindow::on_pushButton_clicked() into:
    void MainWindow::on_pushButton_clicked()
    {
       m_manager->get(QNetworkRequest(QUrl(ui->textEdit->toPlainText())));
    }
    
    • change replyFinished into:
    void MainWindow::replyFinished(QNetworkReply* reply){
    Q_ASSERT(reply);
    QFile file("C:/Users/armin/Desktop/" + reply->url().fileName());
    if(file.open(QIODevice::WriteOnly))
    file.write(reply->readAll());
    else
    qDebug("Save Failed");
    reply->deleteLater();
    }
    

    P.S.
    You are downloading videos, buffering them all in memory before saving them to disk might be a stretch for the RAM of a low-spec PC, dump the data to file as it comes along to prevent running out of memory, see https://forum.qt.io/topic/74397/how-can-i-write-any-data-on-directory/10



  • @VRonin
    Thank you
    Very nice
    Thanks for answer
    my problem is solve
    :))))))))))))))))))))))))))))))))))


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