Phonon VolumeFaderEffect not working with VLC backend

[Harald Sitter]

Unfortunately VolumeFaderEffect is presently not supported by VLC

On Sat, Apr 30, 2022 at 5:57 PM David Jarvie <djarvie at kde.org> wrote:
>
> KAlarm uses Phonon's VolumeFaderEffect. This works with the GStreamer backend,
> but I can't find a way of making it work with VLC. Looking at the phonon-vlc
> code, it looks as if it should work without problem. It's coded as follows:
>
>     mAudioObject = new Phonon::MediaObject(this);
>     mAudioObject->setCurrentSource(source);
>     auto output = new Phonon::AudioOutput(Phonon::NotificationCategory, this);
>     mPath = Phonon::createPath(mAudioObject, output);
>     output->setVolume(mVolume);
>     mFader = new Phonon::VolumeFaderEffect(this);
>     mFader->setVolume(mFadeVolume);
>     mFader->fadeTo(vol, mFadeSeconds * 1000);
>     mPath.insertEffect(mFader);
>
> The values of mVolume and mFadeVolume are between 0 and 1, but whatever I set
> them to, the fader has no effect on VLC. I've tried calling the last line both
> when initialising, or when the Phonon state changes to PlayingState. Can
> someone please advise about what is going wrong?
>
> --
> David Jarvie.
> KDE developer, KAlarm author.