92 lines
3.0 KiB
ReStructuredText
92 lines
3.0 KiB
ReStructuredText
.. _policies_software_dsp:
|
|
|
|
Automatic Software DSP
|
|
======================
|
|
|
|
Introduction
|
|
------------
|
|
|
|
WirePlumber provides a mechanism for transparently handling oddball and embedded
|
|
devices that require software DSP to be done in userspace. Devices such as smartphones,
|
|
TVs, portable speakers, and even some laptops implement an audio subsystem designed
|
|
under the assumption that the hardware sink/source will be "backed" by some sort
|
|
of transparent DSP mechanism. That is, the hardware device itself should not be
|
|
directly accessed, and expects to be sent preprocessed/pre-routed samples. Often,
|
|
especially with Android handsets, these samples are preprocessed or pre-routed
|
|
by the vendor's proprietary userspace.
|
|
|
|
WirePlumber's automatic software DSP mechanism aims to replicate this functionality in
|
|
a standardised and configurable way. The target sink/source is hidden from
|
|
clients of the WirePlumber daemon, and a virtual node is linked to it. This virtual
|
|
node is then presented to clients as *the* node, allowing implementors to specify
|
|
any custom processing or routing in a way that is transparent to users, the kernel,
|
|
and the hardware.
|
|
|
|
|
|
Activating
|
|
----------
|
|
|
|
In addition to the ``node.software-dsp.rules`` section, the ``node.software-dsp``
|
|
component must be activated in the desired profile(s).
|
|
|
|
|
|
Matching a Node
|
|
--------------
|
|
|
|
Matching rules are specified in ``node.software-dsp.rules``. The ``create-filter``
|
|
action specifies behaviour at node insertion. All node properties can be matched
|
|
on, including any type-specific properties such as ``alsa.id``.
|
|
|
|
|
|
Configurable properties
|
|
-----------------------
|
|
|
|
- **filter-graph**
|
|
|
|
SPA-JSON representing a virtual node. This is passed into
|
|
``libpipewire-module-filter-chain`` by ``node/software-dsp.lua``. This property is
|
|
not recursed over - it is returned as a string. In a future
|
|
release, ``filter-graph`` will instead specify the path to a file containing the
|
|
SPA-JSON. The ``node.target`` property of the virtual node should point to
|
|
the node matched by the rule.
|
|
|
|
- **hide-parent**
|
|
|
|
Boolean indicating whether or not the matched node should be hidden from
|
|
clients. ``node/software-dsp.lua`` will set the permissions for all clients other
|
|
than WirePlumber itself to ``'-'``. This prevents use of the node by any
|
|
userspace software except for WirePlumber itself.
|
|
|
|
|
|
Examples
|
|
--------
|
|
|
|
``wireplumber.conf.d/99-my-dsp.conf``
|
|
.. code-block::
|
|
|
|
node.software-dsp.rules = [
|
|
{
|
|
matches = [
|
|
{ "node.name" = "alsa_output.platform-sound.HiFi__Speaker__sink" }
|
|
{ "alsa.id" = "~WeirdHardware*" } # Wildcard match
|
|
]
|
|
|
|
actions = {
|
|
create-filter = {
|
|
filter-graph = {} # Virtual node goes here
|
|
hide-parent = true
|
|
}
|
|
}
|
|
}
|
|
]
|
|
|
|
wireplumber.profiles = [
|
|
main = {
|
|
node.software-dsp = required
|
|
}
|
|
]
|
|
|
|
|
|
This will match any sinks with the UCM HiFi Speaker profile set that are associated
|
|
with cards containing the string "WeirdHardware" at the start of their name.
|