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POOpen and read avi files with OpenCV - Ubuntu
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  1. POOpen and read avi files with OpenCV - Ubuntu
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    copied!<p>I have just read this in the book OpenCV 2 Computer Vision Application Programming Cookbook by R. Laganiere :</p> <blockquote> <p>It is important to note that in order to open the specified video file, your computer must have the corresponding codec installed, otherwise cv::VideoCapture will not be able to understand the input file. Normally, if you are able to open your video file with a video player on your machine (such as the Windows Media Player), then OpenCV should also be able to read this file.</p> </blockquote> <p>Unfortunately, things aren't that easy for me. Yes, I can read avi files on my video player, however it does not work with my OpenCV-Qt application. VideoCapture isOpen() method returns false, despite the fact that the path is correct, and every codec needed seem to be here. I tried several files, so it is not related to one particular format.</p> <p>Does someone here has experience in opening avi files in Ubuntu using OpenCV ? I think this is a big issue, can't find any trully relevant solution on the internet...</p> <p>Thanks !!</p> <p>[EDIT] Here is the function I am working on; some of the variables here are class members, so it may looks incomplete. However, it is this very piece of code that is not working. In particular, the line where I instanciate a new VideoCapture object.</p> <pre><code>void MainWindow::on_actionOuvrir_fichier_triggered() { //mettre a -1 streamId streamId = -1; //get path to the avi file QString fileName = QFileDialog::getOpenFileName(this,tr("Ouvrir fichier video"),"/home", tr("Videos (*.avi)")); std::string utf8_text = fileName.toUtf8().constData(); //open .avi capture = new VideoCapture(utf8_text); //check if(!capture-&gt;isOpened()) cout &lt;&lt; "probleme ouverture fichier video" &lt;&lt; endl; //delay between each frame in ms rate = capture-&gt;get(CV_CAP_PROP_FPS); delay = 1000 / rate; //start Qtimer recordId recordId = startTimer(delay); //capture first frame if(!capture-&gt;read(in)) cout &lt;&lt; "probleme lecture frame fichier video" &lt;&lt; endl; } </code></pre> <p>[EDIT 2] test on Windows 7</p> <pre><code>void MainWindow::on_actionOuvrir_fichier_triggered() { //mettre a -1 streamId streamId = -1; //ouvrir fenetre navigation fichiers pour recuperer path vers .avi QString fileName = QFileDialog::getOpenFileName(this,tr("Ouvrir fichier video"),"/home", tr("Videos (*.avi)")); //std::string utf8_text = fileName.toUtf8().constData(); std::string current_locale_text = fileName.toLocal8Bit().constData(); if(QDir().exists(current_locale_text.c_str())) std::cout &lt;&lt; "Path is good!" &lt;&lt; endl; //ouvrir .avi capture = new VideoCapture(current_locale_text); //check ouverture if(!capture-&gt;isOpened()) cout &lt;&lt; "probleme ouverture fichier video" &lt;&lt; endl; //calculer delay between each frame in ms // rate = capture-&gt;get(CV_CAP_PROP_FPS); // delay = 1000 / rate; //demarrer timer recordId recordId = startTimer(100); //capture premiere frame if(!capture-&gt;read(in)) cout &lt;&lt; "probleme lecture frame fichier video" &lt;&lt; endl; } </code></pre> <p>With that code I was able to open SOME avi files, but not all (actually far from that). So I guess I definitely have a codec issue... does anyone can tell me how to fix this under Ubuntu ? Don't let me go on bounty for that one ! Thank you very much.</p> <p>[EDIT 3] As suggested by <a href="https://stackoverflow.com/users/461338/etienne">Etienne</a>, I followed instructions <a href="http://opencv.willowgarage.com/wiki/VideoCodecs" rel="nofollow noreferrer">here</a> and tried to convert my video to the I420 format supposedly supported by OpenCV on all platforms, using mencoder with the command line given. So I went from 24 bits RGB (RV24) codec to Planar 4:2:0 YUV (I420), according to VLC. Same behavior though, I'm still unable to instanciate the VideoCapture object.</p> <p><a href="https://stackoverflow.com/questions/6971231/first-time-using-open-cv-not-able-to-play-avi-file">THERE IS A LOT OF UNSOLVED CASES</a> similar to mine on Stack Overflow...</p>
 

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