Unable to play a wav file with Audio component

SGaist

Because it's using ALSA directly.

Did you try to build the ALSA backend for Qt Multimedia ?

zyend

Yes, I think so.

I can find libqtaudio_alsa.so in /usr/lib/qt/plugins.

SGaist

Start your application with QT_DEBUG_PLUGINS=1 to see if there's a problem when loading the plugin.

zyend

At first glance, the plugins get loaded.

Got keys from plugin meta data ("alsa")
QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt5/plugins/audio/libqtaudio_alsa.so.new"
Found metadata in lib /usr/lib/qt5/plugins/audio/libqtaudio_alsa.so.new, metadata=
{
    "IID": "org.qt-project.qt.audiosystemfactory/5.0",
    "MetaData": {
        "Keys": [
            "alsa"
        ]
    },
    "className": "QAlsaPlugin",
    "debug": false,
    "version": 328961
}


Got keys from plugin meta data ("alsa")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/pga/audio" ...
loaded library "/usr/lib/qt5/plugins/audio/libqtaudio_alsa.so"

:(

SGaist

Looks good on that point.

Did you check which output QtMultimedia sees as available ?

zyend

What do you mean exactly ?

Yesterday, in the main.cpp, I dumped the

QAudioDeviceInfo::availableDevices(QAudio::AudioOutput)

Is that what you meant ? And yes, it dumps the same devices as with

aplay -L

SGaist

That's that yes and the result also looks good.

Did you check whether the element raises an error ?

zyend

No error raised.

However, in the onClick() handler where idPlay->play() is launched (see code snippet above..),
I traced the values of some properties of tha Audio component.

qml: status =  2
qml: playvolume =  1
qml: muted =  false
qml: error code =  0 , string=
qml: src =  file:///opt/pga/track00.wav
qml: availability =  0
qml: duration =  -1
qml: hasAudio =  false

Weird. duration = -1, hasAudio = false and however, no error code / string...

SGaist

The path to the file looks different from your QML sample code.

zyend

Yes, because I changed the path between my tests, but the paths are valids.

I really don't understand why Qt does not raise any error.
Everything looks correct.
status = 2, that is: "the Media has been loaded".

So it looks like a final phase is not complete. Isn't it ?

SGaist

Can you test the functionality with C++ ?

zyend

I've put this sample code in the C++ side:

init()
{
...
 connect(&m_player, SIGNAL(error(QMediaPlayer::Error)), this, SLOT(on_mediaPlayer_error(QMediaPlayer::Error)));^
 connect(&m_player, SIGNAL(stateChanged(QMediaPlayer::State)), this, SLOT(on_mediaPlayer_stateChanged(QMediaPlayer::State)));^
 connect(&m_player, SIGNAL(mediaStatusChanged(QMediaPlayer::MediaStatus)), this, 
SLOT(on_mediaPlayer_mediaStatusChanged(QMediaPlayer::MediaStatus)));

qDebug() << "Attempt to read mediacontent";
QMediaContent content(QUrl::fromLocalFile("/opt/pga/track00.wav"));
qDebug() << "MediaContent: isNull = " << content.isNull();
m_player.setMedia(content);
m_player.play();
}

Each of the slots above print the value of their respective parameter in stdout.

Output from my host linux:

Attempt to read mediacontent
MediaContent: isNull =  false
<MainWindow::on_mediaPlayer_mediaStatusChanged> status =  QMediaPlayer::LoadingMedia
<MainWindow::on_mediaPlayer_stateChanged> state =  QMediaPlayer::PlayingState
<MainWindow::on_mediaPlayer_mediaStatusChanged> status =  QMediaPlayer::BufferedMedia

Output from my colibri-t20:

Attempt to read mediacontent
MediaContent: isNull =  false
<MainWindow::on_mediaPlayer_mediaStatusChanged> status =  QMediaPlayer::LoadingMedia

It's stuck on LoadingMedia.
No more.

:(

SGaist

Ok...

You should rebuilt the plugin uncommenting the DEBUG_AUDIO define to see if it gives you more information about what is happening.

zyend

Hi,

Unfortunately it doesn't trace more information at all...

Found metadata in lib /usr/lib/qt5/plugins/audio/libqtaudio_alsa.so, metadata=
{
    "IID": "org.qt-project.qt.audiosystemfactory/5.0",
    "MetaData": {
        "Keys": [
            "alsa"
        ]
    },
    "className": "QAlsaPlugin",
    "debug": false,
    "version": 328961
}


Got keys from plugin meta data ("alsa")
QFactoryLoader::QFactoryLoader() checking directory path "/opt/pga/audio" ...
loaded library "/usr/lib/qt5/plugins/audio/libqtaudio_alsa.so"
DeviceInfo name =  "sysdefault:CARD=colibrit20wm971" , codecs =  "audio/pcm"
DeviceInfo name =  "default:CARD=colibrit20wm971" , codecs =  "audio/pcm"
DeviceInfo name =  "default" , codecs =  "audio/pcm"
Default OutputDevice:  "sysdefault:CARD=colibrit20wm971"
Attempt to read mediacontent
MediaContent: isNull =  false
<MainWindow::on_mediaPlayer_mediaStatusChanged> status =  QMediaPlayer::LoadingMedia , bufferStatus =  0
<MainWindow::initialize()> : bufferStatus =  0
screen dpi =  96.1517
screen geo =  QRect(0,0 480x800)
QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt5/plugins/accessiblebridge" ...
QFactoryLoader::QFactoryLoader() checking directory path "/opt/pga/accessiblebridge" ...
QSGContext::initialize: stencil buffer support missing, expect rendering errors
Updating catalog.
<MediaCatalog::roleNames() > called.
qml: size of catalog:  3
qml: playlaunched...status =  1
qml: playvolume =  1
qml: muted =  false
qml: error code =  0 , string=
qml: src =
qml: availability =  0
qml: duration =  -1
qml: hasAudio =  false

SGaist

Does the device info look correct for your system ?
Can you compare with that aplay uses ?

zyend

Yes, it is always the same.

I have also edited the qalsaaudiooutput.cpp and added some fprintf() statements and nothing is displayed in the console.
I put a message in open() and in the constructor

However, it prints loaded library "/usr/lib/qt5/plugins/audio/libqtaudio_alsa.so"

I don't know what I can do to figure out what's happening.

SGaist

Did you install the plugin properly after having built it ?

zyend

What do you mean "install properly" ?

SGaist

Are you sure that the plugin you modified was installed at the right location ?

zyend

Yes.

It was installed under /usr/lib/qt5/plugins/audio