Assistance with editing links via WirePlumber

[Louis DeLosSantos]

Thanks a ton for the info.

I dug at this for awhile and yes, I wound up just calling into the pulse
audio api to switch sink inputs.

I dug enough to find that this file:
https://gitlab.freedesktop.org/pipewire/pipewire/-/blob/master/src/modules/module-protocol-pulse/modules/module-stream-restore.c?ref_type=heads

Is writing to metadata. I kinda quit there, because I couldnt tell if the
metadata it was writing was "stuck" in the pulse audio module or was made
available to the pipewire api proper.

Sounds like from your response that the state that the pa stream restore
module stashes on metadata is indeed available at the "default-metadata"
object that I can retrieve on the registry?

If so, thats great, i can remove the call into pulse-audio library and just
use wireplumber/pipewire.

On Thu, Feb 8, 2024 at 3:46 PM George Kiagiadakis <mail at gkiagia.gr> wrote:

> Hi,
>
> Yes, it is easy to re-link streams to different sinks, similar to
> pavucontrol.
>
> You can do this by setting the “target.object” property in the “default”
> metadata object. The value may be the “node.name" or the “object.serial”
> of the target sink/source that you want to link your stream with.
>
> On the command line:
>
> pw-metadata -n default <ID of the stream> “target.object” “<name of the
> sink>” “Spa:String"
>
> For example:
>
> pw-metadata -n default 45 “target.object”
> “alsa_output.pci-0000_00_1f.3.analog-stereo” “Spa:String"
>
> Using the WirePlumber C API, you need to find the WpMetadata object first,
> using an object manager (use a constraint on “metadata.name” to match
> “default”) and then set the value with:
>
> wp_metadata_set (metadata, stream_node_id, PW_KEY_TARGET_OBJECT,
> “Spa:String”, target_node_name);
>
> PS: If you set the “object.serial” instead of the name, then the type
> should be “Spa:Id” instead.
>
> This is the same mechanism that is used by existing tools like
> pavucontrol. You can also use pavucontrol to see this in action. Use
> “pw-metadata -n default” to print the existing metadata values for
> inspection.
>
> I hope this helps.
>
> Best regards,
> George
>
>
> > On 26 Jan 2024, at 18:09, Louis DeLosSantos <louis.delos at gmail.com>
> wrote:
> >
> > Hey all,
> >
> > I'm writing a Linux desktop shell which will have a built in audio mixer.
> > I'm trying to isolate the API usage to the WirePlumber C API.
> >
> > Is it currently possible to "re-link" input or output streams to a
> > different sink/source via WirePlumber?
> >
> > Is anyone able to point me to examples of doing this? I'm a bit
> > confused about whether I need to delete the existing link and create a
> > new one, or if I can update the existing link with new input/output
> > ports.
> >
> > Thanks a lot.
>
>
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