QtMultimedia 6 - QPulseAudioSink how to set stream name?

[OlegAn]

pa_stream_new_with_proplist function (https://freedesktop.org/software/pulseaudio/doxygen/stream_8h.html#a5bd70e309f09679753499fa198713672) accepts name argument, which is used to distinguish audio streams.
This function is called from QPulseAudioSink::open():

m_stream = pa_stream_new_with_proplist(pulseEngine->context(), m_streamName.constData(),
                                           &m_spec, &channel_map, propList);

But the problem is m_streamName is always initilized like this (in the same open() method):

    if (m_streamName.isNull())
        m_streamName =
                QStringLiteral("QtmPulseStream-%1-%2").arg(::getpid()).arg(quintptr(this)).toUtf8();

This makes the stream name a random string every app launch ("QtmPulseStream-...."), making it impossible to remember which output device to use (for example, there's such setting in KDE, but random stream name makes this setting single-shot and thus useless).

I can probably add output device setting in my app, or inherit QAudioSink and hack it somehow, but this is not the question here. The question is how to set m_streamName? Or is it designed to be random like this?

This problem does not exists in Qt5+gstreamer, there stream name is always equal to application name and the association app->device is preserved between restarts. No idea how it happens b/c the code for QPulseAudioSink is identical.

In Qt6 when using QT_MEDIA_BACKEND=gstreamer the behavior is slightly different: I see app name in as the stream name in KDE audio settings, but it still does not remember the association app-to-device, so it seems like there's randomness still. Also, no idea how backend changes audio sink behavior, does ffmpeg or gtreamer override stream name afterwards?