QMediaPlayer gives me wrong informations about video

Question

I'm trying to implement a server terminal application which inspects video files. I need to get informations like audio/video codec, resolution, bitrate, length, etc.

I found most of the needed information in QMediaResource. After reading multiple examples, I came to this:

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QMediaPlayer media;
    media.setMedia(QUrl::fromLocalFile("/home/danbru1211/Videos/S01E01.mp4"));

    QObject::connect(&media, &QMediaPlayer::mediaStatusChanged,
                     [&media](QMediaPlayer::MediaStatus status){
        qDebug() << status;

        auto resource = media.media().canonicalResource();
        qDebug() << "language" << resource.language();
        qDebug() << "audioCodec" << resource.audioCodec();
        qDebug() << "videoCodec" << resource.videoCodec();
        qDebug() << "dataSize" << resource.dataSize();
        qDebug() << "audioBitRate" << resource.audioBitRate();
        qDebug() << "sampleRate" << resource.sampleRate();
        qDebug() << "channelCount" << resource.channelCount();
        qDebug() << "videoBitRate" << resource.videoBitRate();
        qDebug() << "resolution" << resource.resolution();
    });

    return a.exec();
}

But sadly this does not output the right meta data:

QMediaPlayer::LoadedMedia
language ""
audioCodec ""
videoCodec ""
dataSize 0
audioBitRate 0
sampleRate 0
channelCount 0
videoBitRate 0
resolution QSize(-1, -1)

I am sure the path of the video exists and is readable. Why do I get all 0 values and not the correct ones. Is this the right/best way to get meta informations about a video file in Qt?

Answer 1

Given the fact that QtMultimedia in general is pretty much broken, you should listen to QMediaObject::metaDataChanged (inherited by QMediaPlayer).

However, I warn you that this is broken on Windows and most likely macOS too. I've reported several QTBUG and they just don't care.