Hello, some mkv movies embed DVD cover. I am looking for getting this cover and displaying as icon for this movie in Dolphin. For that, I got source code from mplayerthumbs and I attempt to modify it to add this feature. My main problem is I have only some notions in c++ but not in qt, nor about KDE libraries. However, I started. For the moment, I added GetMkvCover method in videopreview.cpp file. This is the code

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/***************************************************************************
   Copyright (C) 2006-2008
   by Marco Gulino <marco@kmobiletools.org>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the
   Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
 ***************************************************************************/

#include "videopreview.h"

#include <qfile.h>
#include <qpixmap.h>
#include <qimage.h>
#include <QtCore/QVarLengthArray>

#include <kstandarddirs.h>
#include <kmimetype.h>
#include <QDir>
#include <QString>
#include <qpainter.h>
#include <krandomsequence.h>
#include <qdatetime.h>
#include <qregexp.h>
#include "videopreview.h"
#include <QProcess>
#include <kdebug.h>
#include <ktempdir.h>
#include <kurl.h>
#include <math.h>
#include <qfileinfo.h>
#include <kcodecs.h>

#include "mplayerthumbs.h"

#include <iostream>
#include <unistd.h>

#define DBG_AREA

//#include "config.h"
extern "C"
{
    KDE_EXPORT ThumbCreator *new_creator()
    {
        return new VideoPreview;
    }
}

VideoPreview::VideoPreview()
    : m_data(0),
      m_dataSize(0)
{
}

VideoPreview::~VideoPreview()
{
    delete [] m_data;
    delete tmpdir;
    delete rand;
    delete mplayerprocess;
}

bool VideoPreview::startAndWaitProcess(const QStringList &args) {
    kDebug(DBG_AREA) << "videopreview: starting process with args: " << args << endl;
    mplayerprocess->start( args.join(" ") );
    if(! mplayerprocess->waitForStarted() ) {
        kDebug(DBG_AREA) << "videopreview: PROCESS NOT STARTED!!! exiting\n";
        return false;
    }
    if(! mplayerprocess->waitForFinished() ) {
        kDebug(DBG_AREA) << "videopreview: PROCESS DIDN'T FINISH!! exiting\n";
        mplayerprocess->close();
        return false;
    }
  kDebug() << "videopreview: process started and ended correctly\n";
  return true;
}

bool VideoPreview::create(const QString &path, int width, int height, QImage &img)
{
    MPlayerThumbsCfg *cfg=MPlayerThumbsCfg::self();
    QFileInfo fi(path);
        kDebug(DBG_AREA) << "videopreview: file extension=\"" << fi.suffix().trimmed() << "\"\n";
        if( fi.suffix().trimmed().length() && !cfg->noextensions().filter(fi.suffix().trimmed(), Qt::CaseInsensitive)
         .isEmpty() )
    {
        delete cfg;
        kDebug(DBG_AREA) << "videopreview: matched extension " << fi.suffix().prepend('.') << "; exiting.\n";
        return false;
    }
    playerBin=cfg->mplayerbin();
    customargs=cfg->customargs().split(" ");
    kDebug(DBG_AREA) << "videopreview: customargs=" << cfg->customargs() << " ;;;; " << customargs << endl;
    delete cfg;
    if(playerBin.length()) kDebug(DBG_AREA) << "videopreview: found playerbin from config: " << playerBin << endl;
    else
    {
        playerBin=KStandardDirs::findExe("mplayer-bin");
        if(!playerBin.length()) playerBin=KStandardDirs::findExe("mplayer");
        if(!playerBin.length())
        {
            kDebug(DBG_AREA) << "videopreview: mplayer not found, exiting. Run mplayerthumbsconfig to setup mplayer path manually.\n";
            return false;
        }
        kDebug(DBG_AREA) << "videopreview: found playerbin from path: " << playerBin << endl;   
    }

    mkvextractBin=KStandardDirs::findExe("mkvextract");
    if(!mkvextractBin.length())
      {
   kDebug(DBG_AREA) << "mkvcreator: mkvextract not found, exiting.\n";
   return false;
      }
    kDebug(DBG_AREA) << "mkvcreator: found mkvextractbin from path: " << mkvextractBin << endl;

    fileinfo.seconds=0;
    fileinfo.fps=0;
    tmpdir=new KTempDir();
    if(tmpdir->name().isNull() ) return false;
    kDebug(DBG_AREA) << "videopreview: using temp directory " << tmpdir->name() << endl;

    rand=new KRandomSequence(QDateTime::currentDateTime().toTime_t());
    mplayerprocess=new QProcess();
    int flags=0;
    KUrl furl(path);
    kDebug(DBG_AREA) << "videopreview: url=" << furl << "; local:" << furl.isLocalFile() << endl;
    fileinfo.towidth=width;
    fileinfo.toheight=height;
    QPixmap pix;
//    if(furl.isLocalFile())
//    {
    flags=framerandom;
    QStringList args;
    args << playerBin << QString("\"" + path + "\"") << "-nocache" << "-identify" << "-vo" << "null" << "-frames" << "0"/* << "-nosound" */<< "-ao" << "null";
    args+= customargs;

    kDebug(DBG_AREA) << "videopreview: starting process: --_" << " " << args.join(" ") << "_--\n";
    if (! startAndWaitProcess(args) ) return NULL;

    QString information=QString(mplayerprocess->readAllStandardOutput() );
//     kDebug(DBG_AREA) << "videopreview: output from process: " << information << endl;
    QRegExp findInfos("ID_VIDEO_FPS=([\\d]*).*ID_LENGTH=([\\d]*).*");
    if(findInfos.indexIn( information) == -1 )
    {
        kDebug(DBG_AREA) << "videopreview: No information found, exiting\n";
        return NULL;
    }
    fileinfo.seconds =findInfos.cap(2).toInt();
    fileinfo.fps=findInfos.cap(1).toInt();
   
    kDebug(DBG_AREA) << "videopreview: find length=" << fileinfo.seconds << ", fps=" << fileinfo.fps << endl;
/*    } else
    {
        flags=frameend;
    }*/
#define LASTTRY 3
    for(int i=0; i<=LASTTRY; i++)
    {
        kDebug(DBG_AREA) << "videopreview: try " << i << endl;
        pix=getFrame(path, ((i<LASTTRY) ? flags : framestart ) );
        if(!pix.isNull()) {
            uint variance=imageVariance(pix.toImage()/*.bits(),( (width+ 7) & ~0x7), width, height, 1 */);
            kDebug(DBG_AREA) << "videopreview: " << QFileInfo(path).fileName() << " frame variance: " << variance << "; " <<
                    ((variance<=40 && ( i!=LASTTRY-1))? "!!!DROPPING!!!" : "GOOD :-)" ) << endl;
            if(variance>40 || i==LASTTRY-1 ) break;
        }
    }
    if(pix.isNull() )
    {
        tryUnlink(tmpdir);
        return false;
    }
    /** From videocreator.cpp - xine_artsplugin
    Copyright (C) 2002 Simon MacMullen
    Copyright (C) 2003 Ewald Snel <ewald@rambo.its.tudelft.nl>
     * */
//     QPixmap pix( createThumbnail( &frame, width, height ) );
//#ifdef STRIPS_SUPPORT
    if(cfg->createStrips() ) {
        QPainter painter( &pix );
        QPixmap sprocket;

        kDebug(DBG_AREA) << "videopreview: using strip image sprocket: " << KStandardDirs::locate( "data", "videothumbnail/sprocket-small.png" ) << endl;
        if (pix.height() < 60)
            sprocket = QPixmap(KStandardDirs::locate( "data", "videothumbnail/sprocket-small.png" ));
        else if (pix.height() < 90)
            sprocket = QPixmap(KStandardDirs::locate( "data", "videothumbnail/sprocket-medium.png" ));
        else
            sprocket = QPixmap(KStandardDirs::locate( "data", "videothumbnail/sprocket-large.png" ));

        for (int y = 0; y < pix.height() + sprocket.height(); y += sprocket.height()) {
            painter.drawPixmap( 0, y, sprocket );
        }
}
        // End of xine-artsplugin code
//#endif

    if(cfg->useMkvCover() && fi.suffix().trimmed().length() && !cfg->noextensions().filter(fi.suffix().trimmed(), Qt::CaseInsensitive).isEmpty() ) {
     
      QPixmap mkvpix;
      QStringList args;
      args << mkvextractBin << "attachments" << QString("\"" + path + "\"") << "4:cover.jpg";
     
      kDebug(DBG_AREA) << "mkvcreator: starting process: --_" << " " << args.join(" ") << "_--\n";
      if (! startAndWaitProcess(args) ) return NULL;
     
      mkvpix=getMkvCover(path);
      if(!mkvpix.isNull() )
   pix = mkvpix;
      else {
   tryUnlink(tmpdir);
   return false;
      }
    }
    img = pix.toImage();
   
    tryUnlink(tmpdir);
    return true;
}

void VideoPreview::tryUnlink(KTempDir *dir) {
    if(dir) dir->unlink();
}

QPixmap VideoPreview::getFrame(const QString &path, int flags)
{
    QStringList args;
    kDebug(DBG_AREA) << "videopreview: using flags " << flags << endl;
#define START ((fileinfo.seconds*15)/100)
#define END ((fileinfo.seconds*70)/100)
    args.clear();
    args << playerBin << "\"" + path + "\"";
    if(fileinfo.towidth>fileinfo.toheight) fileinfo.toheight=-2; else fileinfo.towidth=-2;
//     switch( flags ){
//         case random
//     }
    if( flags & framerandom )
    {
        kDebug(DBG_AREA) << "videopreview: framerandom\n";
        unsigned long start=(unsigned long)(START+(rand->getDouble() * (END - START) ) );
        args << "-ss" << QString::number( start )
                << "-frames" << "4";
    } else if (flags & frameend )
    {
        kDebug(DBG_AREA) << "videopreview: frameend\n";
        args << "-ss" << QString::number( fileinfo.seconds - 10 )
                << "-frames" << "4";
    } else if (flags & framestart)
    {
        kDebug(DBG_AREA) << "videopreview: framestart\n";
        if(!fileinfo.fps) fileinfo.fps=25; // if we've not autodetected a fps rate, let's assume 25fps.. even if it's wrong it shouldn't hurt.
        // If we can't skip to a random frame, let's try playing 10 seconds.
        args << "-frames" << QString::number( fileinfo.fps*10 );
    }
    KMD5 md5builder(path.toLatin1() );
    QString md5file=md5builder.hexDigest().data();
    QString tmpDirPath = tmpdir->name() + md5file + QDir::separator();
    args << "-nocache" << "-idx" /*@TODO check if it's too slow..*/ << "-ao" << "null"/*"-nosound" << */<< "-speed" << "99"  /*<< "-sstep" << "5"*/
            << "-vo" << QString("jpeg:outdir=%1").arg(tmpDirPath ) << "-vf" << QString("scale=%1:%2").arg(fileinfo.towidth).arg(fileinfo.toheight);
    args+=customargs;

    if (! startAndWaitProcess(args) ) return NULL;

    kDebug(DBG_AREA) << "videopreview: temp dir '" << tmpDirPath << "'\n";

    if (QDir(tmpDirPath ).entryList( QStringList("*.jpg") ).isEmpty() ) return false;

    QString lastframe=QDir(tmpDirPath ).entryList( QStringList("*.jpg") ).last();
    kDebug(DBG_AREA) << "videopreview: LastFrame==" << lastframe << endl;
    QPixmap retpix(tmpDirPath.append( lastframe ));
    return retpix;
}

QPixmap VideoPreview::getMkvCover(const QString &path)
{
  QStringList args;
  args.clear();
  args << mkvextractBin << "attachments" << "\"" + path + "\"";
 
  KMD5 md5builder(path.toLatin1() );
  QString md5file=md5builder.hexDigest().data();
  QString tmpDirPath = tmpdir->name() + md5file + QDir::separator();
  //    mkvextract attachments "Le convoyeur.mkv" 4:cover.jpg;
  args << QString("4:%1/cover.jpg").arg(tmpDirPath);
 
  if (! startAndWaitProcess(args) ) return NULL;
 
  kDebug(DBG_AREA) << "mkvcreator: temp dir '" << tmpDirPath << "'\n";
 
  if (QDir(tmpDirPath ).entryList( QStringList("*.jpg") ).isEmpty() ) return false;
 
  QString lastcover=QDir(tmpDirPath ).entryList( QStringList("*.jpg") ).last();
  kDebug(DBG_AREA) << "mkvcreator: LastCover==" << lastcover << endl;
  //  std::cout << "mkvcreator: LastCover==" << lastcover.toAscii().data() << std::endl;
  QPixmap retpix(tmpDirPath.append( lastcover ));
  return retpix;
}

ThumbCreator::Flags VideoPreview::flags() const
{
    return (Flags)(DrawFrame);
}


uint VideoPreview::imageVariance(QImage image )
{
    uint delta=0;
    uint avg=0;
    uint bytes=image.numBytes();
    uint STEPS=bytes/2;
    QVarLengthArray<uchar> pivot(STEPS);
    kDebug(DBG_AREA) << "Using " << STEPS << " steps\n";
    uchar *bits=image.bits();
    // First pass: get pivots and taking average
    for( uint i=0; i<STEPS ; i++ ){
        pivot[i]=bits[i*(bytes/STEPS)];
        avg+=pivot[i];
    }
    avg=avg/STEPS;
    // Second Step: calculate delta (average?)
    for (uint i=0; i<STEPS; i++)
    {
        int curdelta=abs(int(avg-pivot[i]));
        delta+=curdelta;
    }
    return delta/STEPS;
}
#include "videopreview.moc"

I have also added few things in create methode at the end to take into account this new possibility. And also little modifications in the GUI to add a button to toggle this option. My problem is the actual code does not work and I do not why. So to start, I woulg like to debug my code veriying step by step. Usually, I put cout a bit everywhere. Here, it looks we use kdebug but I did not understand how it works. Could you explain to me this point. Thanks in advance.

kDebug() will output the message in question if the debug area is enabled. You can enable debug areas using "kdebugdialog".

Thanks for your answer. I got now some messages when I run mplayerthumbsconfig but only if I change something in the GUI. I do not see anything about the thumbnail generation. How can I show message about thumbnail. For example, I never see

kDebug(DBG_AREA) << "videopreview: starting process with args: " << args << endl;

whereas thumbnails are generated by mplayerthumbs.
Sorry if it is a stupid question...

Absence of this in KDE (and XFCE) is the sole cause of my imprisonment in otherwise ridiculous Gnome 3. Without a visual cue (embedded DVD covers in MKV files) you can't have a functional video library. This would be a much better feature than bouncing icons. Yet sadly even someone's help request in implementing this is not answered.

Sorry, I missed the response for some reason.

You may need to enable KDebug output. The easiest way to do this is by using "kdebugdialog". Make sure to enable all areas, then try.

Glad to hear that it was not intentional. Hopefully the original poster makes use of this.