Details
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Bug
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Resolution: Unresolved
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P2: Important
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None
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6.5.0, 6.5.1, 6.5.2, 6.5.3, 6.6.0, 6.6.1, 6.6.2, 6.6.3, 6.7.0 FF, 6.7.0 Beta1, 6.7.0 Beta2, 6.7.0 Beta3, 6.7.1, 6.7.2, 6.8.0 Beta1, 6.8.0 Beta2
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Linux odroidh2 5.15.0-75-generic #82~20.04.1-Ubuntu SMP Wed Jun 7 19:37:37 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Ubuntu 20.04.6 LTS
ALSA setup:
pcm.!default {
type plug
slave.pcm "hw:XSPDIF3"
}
pcm.!sysdefault {
type plug
slave.pcm "hw:XSPDIF3"
}
ctl.!default {
type hw
card XSPDIF3
}
ctl.!sysdefault {
type hw
card XSPDIF3
}
Linux odroidh2 5.15.0-75-generic #82~20.04.1-Ubuntu SMP Wed Jun 7 19:37:37 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux Ubuntu 20.04.6 LTS ALSA setup: pcm.!default { type plug slave.pcm "hw:XSPDIF3" } pcm.!sysdefault { type plug slave.pcm "hw:XSPDIF3" } ctl.!default { type hw card XSPDIF3 } ctl.!sysdefault { type hw card XSPDIF3 }
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Linux/Wayland,
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Multimedia Next Next
Description
QtMultimedia based QML Audio and Video playback applications that worked correctly on a Linux system (Lubuntu 20.04 based dedicated media server and player) without PulseAudio installed, fail to play back audio when using the default FFMPEG backend introduced in Qt6.5.0, 6.5.1 and 6.6.0.
Formerly, with the gstreamer-based backend used for Qt5.15-Qt6.4.x, these apps played back successfully on this pulse-audio-less system using ALSA alone, with an asoundrc profile that sets the ALSA default and sysdefault device to a specific soundcard and device such that gst-play-1.0 "just works" as do gstreamer based Qt5 and Qt6 apps for versions <6.5.
Now, with 6.5.0, 6.5.1, and 6.6.0, when using the default FFMPEG backend, no audio is output no matter what. An error message suggests the problem is that the FFMPEG backend expects pulseaudio but doesn't find it:
PulseAudioService: pa_context_connect() failed
The source code indicates an ALSA backend exists under directory
6.6.0/Src/qtmultimedia/src/multimedia/alsa
however there is no clear way (e.g. environment variable) to force ALSA to be invoked over the default pulseaudio service at
6.6.0/Src/qtmultimedia/src/multimedia/pulseaudio
The only solution to get audio working with Qt>=6.5 on a Linux system without pulseaudio is to force the gstreamer backend via environment variable:
QT_MEDIA_BACKEND=gstreamer
With this environment variable forcing the gstreamer backend, audio playback works again on a pulseaudio-less Linux system using only ALSA.
IMHO, the new ffmpeg media backend should not just abort with a warning on missing pulseaudio, but should then fall-back to use ALSA directly, which is what gstreamer already does.