Unable to play a wav file with Audio component

zyend

Hi all,

Now 3 days I'm stuck with a tricky issue!
I've built an image for my embedded device based on a Colibri T20 board, using Yocto.
I"ve added Qt5, using X11 (because Tegra20 drivers from nvidia support hw accel only with X11...).
At this point, everything works fine.
I've also generated the respective SDK to build application for the respective platform..
Works fine.

I wrote a simple application to play audio file, very basic...just to play wav files...
It does not work. No sound output.

import QtMultimedia 5.5

Item {

...
Audio {
 id: audioPlayer
source: "file:///opt/track.wav"
}
..
onClick() {
  idPlayer.play()
}

}

This code works fine on my host linux.
But not on my Colibri.
Qt 5.5.1 was firstly built with ALSA, pulseaudio (gstreamer plugins...).
No outpût.

But in the linux, I can play the wav file using:

aplay /opt/track.wav

So I assume that my alsa driver are up-to-date.

Then, I 've recompiled Qt 5.5.1 without pulseaudio....
It does not work better :(

To be honnest, I'm not very experienced with alsa and pulseaudio matter. I'm very fustrated bzecause I don't understand what's happening under the abstracted layer of QtMultuimedia.

Any suggestion is welcome...This issue is simply driving me mad ;)

K.

SGaist

Hi,

Do you see any error message on the console ?

zyend

SGaist,

Before recompîling Qt5.51 without pulseaudio, I had the following message in the console:

PulseAudioService: pa_context_connect() failed

Unfortunately, recompiling without pulseaudio doesnot display the message anymore...but it doesn't fix anything. I can't hear anything :(

K.

SGaist

Do you have Pulseaudio running on your device ?

zyend

No.
I've removed "pulseaudio" from the Yocto generated Distro.

But the command line:

aplay /opt/track.wav

still works though...

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 ?