[pulseaudio-discuss] How to create a virtual microphone with source set as default monitor device?

[guest271314]

> Electron is a whole separate discussion. Electron applications have
different levels of access to the system than the vanilla chromium
browser.

Native Messaging provides access to the system.

> With the amount of work you're seeming to have put into workarounds,
maybe you would be better off writing a proper native application?

Yes. Am filtering the most consistent approach. Am far more familiar
with front-end (HTML, JavaScript) than
C, C++, Rust, etc., thus most of the workarounds are web platform
based. From perspective here there should be a very simple function,
captureSystemAudio() that does only that.

On Tue, Sep 8, 2020 at 9:24 PM Sean Greenslade <sean at seangreenslade.com> wrote:
>
> On Mon, Sep 07, 2020 at 05:03:59PM -0700, guest271314 wrote:
> > > I doubt that will be possible. Pavucontrol makes use of the native
> > > pulseaudio APIs, which are not exposed to javascript.
> >
> > If mpv can be embedded in an HTML document
> > https://github.com/Kagami/mpv.js it should be possible to embed
> > pavucontrol or pavucontrol-qt
> > (https://doc.qt.io/qt-5/qtwebchannel-javascript.html ;
> > https://medium.com/@petar.koretic/why-you-should-use-qt-qml-for-you-next-cross-platform-application-part-1-desktop-5e6d8856b7b4)
> > in particular in a browser; for example using WebAssembly; WASI;
> > Native Messaging; at least the ability to control Recording tab (-t 2)
> > from JavaScript or an HTML form.
>
> Electron is a whole separate discussion. Electron applications have
> different levels of access to the system than the vanilla chromium
> browser.
>
> > > After reading through those bug reports and related issue links, it's
> > > pretty clear that this is not a use case that they are particularly
> > > interested in supporting.
> >
> > The majority of own repositories at github are dedicated to fixing
> > WontFix; supporting SSML parsing; variable width and height video
> > capture with ability to merge multiple tracks into a single media
> > container, or stream media without a container; streaming audio
> > potentially infinite input streams, that is, a dynamic Internet radio
> > station; capturing speech synthesis output from Web Speech API, which
> > is the origin of this use case of capturing system audio output.
> >
> > > May I perhaps suggest using a different
> > > browser?  Firefox had no problem with monitor inputs last time I
> > > checked.
> >
> > Interestingly, am completing testing of another workaround where since
> > Firefox does capture monitor devices, a new, dedicated instance of
> > Nightly is started prior to launching Chromium, the MediaStreamTrack
> > and MediaStream therefrom are added to a WebRTC RTCPeerConnection, and
> > currently using clipboard for signaling which is not ideal though is
> > one way to exchange text data between different browsers, accessing
> > the monitor device at Chromium instance generated at Nightly
> > https://gist.github.com/guest271314/04a539c00926e15905b86d05138c113c.
> > That approach avoids writing and reading raw PCM to memory.
>
> With the amount of work you're seeming to have put into workarounds,
> maybe you would be better off writing a proper native application?
>
> > > No idea, I've never done it myself. The example listed in the online
> > > docs shows a simple stereo swap, so you could presumably adapt it by
> > > switching the channels to be non-swapped (and of course substitute your
> > > specific master source name).
> >
> > Not sure precisely how to begin.
> >
> > Am still trying to gather the specific commands in code that
> > pavucontrol uses when setting the stream at the UI. Am not certain
> > what to pass to pactl move-source-output at what time
> > https://gitlab.freedesktop.org/pulseaudio/pavucontrol/-/issues/91#note_590795.
>
> If you read the documentation (e.g. man pactl), it seems pretty
> straightforward:
>
> > move-source-output ID SOURCE
> >      Move the specified recording stream (identified by its numerical index) to the specified source (identified by its symbolic name or numerical index).
>
> So you need to find the specific source output index (ID) and your new
> target source (SOURCE). I started an audacity session recording my
> microphone, and ran the "pactl list source-outputs" command. This gave
> me the index. I then ran the "pactl list sources" to find my target
> source name. The switch command (for my setup) then looked like this:
>
> > pactl move-source-output 203 pulse_send_nofx.monitor
>
> --Sean
>
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