Seek in Sound File

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I tried to play a sound file not at the beginning but with an offset of 20 seconds.

The following way of setting an offset fails:

player = new QMediaPlayer(this); player->setMedia(QUrl::fromLocalFile("myCoolSong.mp3")); player->setVolume(50); player->play(); // music can be heard qDebug() << player->isSeekable(); // is always false player->setPosition ( 20*1000 ); //does not work

It does not work because QMediaPlayer works asynchronously.

As soon as the seek operations are delayed everything works as intended. For example:

CoolPlayer::on_Button1_clicked() {

qDebug() << player->isSeekable(); // true
player->setPosition ( 20*1000 );

}

To make my life easier I have derived a class MediaPlayer from QMediaPlayer and added a blocking load method:

void MediaPlayer::loadBlocking(const QString &file;) {

setMedia(QUrl::fromLocalFile(file));
if(!isSeekable())
{
QEventLoop loop;
QTimer timer;
timer.setSingleShot(true);
timer.setInterval(2000);
loop.connect(&timer;, SIGNAL (timeout()), &loop;, SLOT (quit()) );
loop.connect(this, SIGNAL (seekableChanged(bool)), &loop;, SLOT (quit()));
loop.exec();
}

}

When files are loaded with this blocking load method setPosition() can be called right in the next source line. loadBlocking blocks until signal seekableChanged() is emitted. To avoid a deadlock, maximum waiting time is 2 seconds.