More sound simultaneously with QSoundEffect and alsa

yeckel

Hi,
I'm working on a custom ARM board and I should get sounds working in Qt5.5. At the beginning just one sound in one time could be played uing QSoundEffect and aplay. Then I've configured /etc/asound.cfg for using alsa mixer plugin dmix and that default output for alsa should be the mixer:

pcm.dmixed {
    type dmix
    ipc_key 1024
    ipc_key_add_uid 0
    slave.pcm "hw:0,0"
}
pcm.dsnooped {
    type dsnoop
    ipc_key 1025
    slave.pcm "hw:0,0"
}

pcm.duplex {
    type asym
    playback.pcm "dmixed"
    capture.pcm "dsnooped"
}

pcm.!default {
    type plug
    slave.pcm "duplex"
}

ctl.!default {
  type hw
  card 0
}

From this time can I play more aplay, however the QT app is able to play just one sound (on desktop linux more).

QAudioDeviceInfo::defaultOutputDevice().deviceName():
Default device name: "sysdefault:CARD=DatAudio"

QAudioDeviceInfo::availableDevices(QAudio::AudioOutput):
Device Name: "sysdefault:CARD=DatAudio"
Preferred Format: "audio/pcm"
Device Name: "default"
Preferred Format: "audio/pcm"

I suppose the QT is using wrong output (not default). According the strace the /etc/asound.conf is read as well as alsa plugin /usr/lib/qt/plugins/audio/libqtaudio_alsa.so (there is no other available)

What can I do to change the output? Is that the right way? Thanks.

SGaist

Hi,

I think the best thing to do would be to check the Alsa plugin source to see what it's doing and maybe modify it for your purpose.

Hope it helps.

yeckel

Ok it was a bug in qt5/qtmultimedia/src/plugins/alsa/qalsaaudiooutput.cpp method bool QAlsaAudioOutput::open() which is fixed in QT5.7

The old version was explicitly opening alsa device hw:0 and the 5.7 version is using the proper "default" device as specified in /etc/asound.cfg

SGaist

Glad you found out and thanks for sharing ! :)

Happy hacking !