PipeWire: Native Protocol

PipeWire 1.4.2 |

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Native Protocol

PipeWire has a pluggable client/server IPC protocol.

The reference implementation uses unix sockets and is implemented in Protocol Native.

We document the messages here.

# Message header

Each message on the unix socket contains a 16 bytes header and a variable length payload size:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| opcode | size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| seq |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| n_fds |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| payload POD |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional footer POD |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
seq
uint32_t int seq
Definition core.h:432

These are four uint32 words to be read in native endianness.

- Id: the message id this is the destination resource/proxy id
- opcode: the opcode on the resource/proxy interface
- size: the size of the payload and optional footer of the message
- seq: an increasing sequence number for each message
- n_fds: number of file descriptors in this message.

The sender should send along with each message the fds that belong to the message. If there are more than the maximum number of fds in the message than can fit in one message, the message is split into multiple parts.

A receiver needs to first read the header to know the size of the complete message. After collecting the complete message, it can start processing it.

The payload is a single POD see SPA POD for details.

After the payload, there is an optional footer POD object.

# Making a connection

First a connection is made to a unix domain socket. By default, the socket is named as "pipewire-0" and searched in the following directories:

- getenv("PIPEWIRE_RUNTIME_DIR")
- getenv("XDG_RUNTIME_DIR")
- getenv("USERPROFILE")

The client opens the socket and allocates a Core proxy with id 0 and a Client proxy with id 1. The proxy is nothing more than a way to identify the remote objects with an id. Usually they also contain the type and version of the remote object and some helpers (interfaces) to dispatch messages.

The server will allocate a new Core resource with id 0. Resources are the counterpart of client proxies and also typically contain extra information and helpers (interfaces) to dispatch messages.

The client sends the Core::Hello message on the socket to start the communication.

The server binds the client resource with id 1 to the client. This means that the client object on the server will now have a resource with a client side proxy associated with it.

When the client sends a message for a certain proxy, the server side resource with the same id for the client is found and the message is dispatched to the object associated with the resource.

Similarly when a server sends a message on a resource, the client will find the proxy with the same id and dispatch the message to it's associated object.

The client then sends client properties to the server.

client server
|---------------------------------------->|
| open socket |
| |
|---------------------------------------->|
| Core::Hello(version) |
| |
|---------------------------------------->|
| Client::UpdateProperties |
. .

This completes the setup of the client. The newly connected client will appear in the registry at this point.

# Core proxy/resource

The core is always the object with Id 0.

## Core Methods (Id 0)

### Core::Hello (Opcode 1)

The first message sent by a client is the Hello message and contains the version number of the client.

Struct(
Int: version
)

The version is 3.

### Core::Sync (Opcode 2)

The Sync message will result in a Done event from the server. When the Done event is received, the client can be sure that all operations before the Sync method have been completed.

Struct(
Int: id
Int: seq
)

- id: the id will be returned in the Done event.
- seq: is usually generated automatically and will be returned in the Done event.

### Core::Pong (Opcode 3)

Is sent from the client to the server when the server emits the Ping event. The id and seq should be copied from the Ping event.

Struct(
Int: id
Int: seq
)

### Core::Error (Opcode 4)

An error occurred in an object on the client.

Struct(
Int: id
Int: seq
Int: res
String: message
)
message
uint32_t int int const char * message
Definition core.h:433
res
uint32_t int int res
Definition core.h:433

- id: The id of the proxy that is in error.
- seq: a seq number from the failing request (if any)
- res: a negative errno style error code
- message: an error message

### Core::GetRegistry (Opcode 5)

A client requests to bind to the registry object and list the available objects on the server.

Like with all bindings, first the client allocates a new proxy id and puts this as the new_id field. Methods and Events can then be sent and received on the new_id (in the message Id field).

Struct(
Int: version
Int: new_id
)

- version: the version of the registry interface used on the client
- new_id: the id of the new proxy with the registry interface

After this method, the server will start sending Registry::Global events to the proxy with new_id.

client server
| |
| new proxy(new_id) |
|---------------------------------------->| new resource(new_id)
| Core::GetRegistry(version) |
| |
|<----------------------------------------| new_id
| Registry::Global() |
|<----------------------------------------|
| Registry::Global() |
. .

There is no explicit last Global event to signal that the last object has been received. The usual way of knowing this is to send a Core::Sync method right after the Core::GetRegistry method and to wait for the Core::Done event.

client server
| |
| new proxy(new_id) |
|---------------------------------------->| new resource(new_id)
| Core::GetRegistry(version) |
|---------------------------------------->|
| seq = Core::Sync |
| |
|<----------------------------------------| new_id
| Registry::Global() |
|<----------------------------------------|
| Registry::Global() |
. .
|<----------------------------------------|
| Core::Done(seq) |
. .

### Core::CreateObject (Opcode 6)

Create a new object from a factory of a certain type.

The client allocates a new_id for the proxy. The server will allocate a new resource with the same new_id and from then on, Methods and Events will be exchanged between the new object of the given type.

Struct(
String: factory_name
String: type
Int: version
Struct(
Int: n_items
(String: key
String: value)*
): props
Int: new_id
)

- factory_name: the name of a server factory object to use
- type: the type of the object to create, this is also the type of the interface of the new_id proxy.
- props: extra properties to create the object
- new_id: the proxy id of the new object

### Core::Destroy (Opcode 7)

Destroy an object.

Struct(
Int: id
)

- id: the proxy id of the object to destroy.

## Core Events

Core events are emitted by the server.

### Core::Info (Opcode 0)

Emitted by the server upon connection with the more information about the server.

Struct(
Int: id
Int: cookie
String: user_name
String: host_name
String: version
String: name
Long: change_mask
Struct(
Int: n_items
(String: key
String: value)*
): props
)

- id: the id of the server (0)
- cookie: a unique cookie for this server
- user_name: the name of the user running the server
- host_name: the name of the host running the server
- version: a version string of the server
- name: the name of the server
- change_mask: a set of bits with changes to the info
- props: optional key/value properties, valid when change_mask has (1<<0)

### Core::Done (Opcode 1)

Emitted as a result of a client Sync method.

Struct(
Int: id
Int: seq
)

id and seq are passed from the client Sync request.

### Core::Ping (Opcode 2)

Emitted by the server when it wants to check if a client is alive or ensure that it has processed the previous events.

Struct(
Int: id
Int: seq
)

- id: the object id to ping
- seq: usually automatically generated. The client should pass this in the Pong method reply.

### Core::Error (Opcode 3)

The error event is sent out when a fatal (non-recoverable) error has occurred. The id argument is the proxy object where the error occurred, most often in response to a request to that object. The message is a brief description of the error, for (debugging) convenience.

Struct(
Int: id
Int: seq
Int: res
String: message
)

- id: The id of the resource that is in error.
- seq: a seq number from the failing request (if any)
- res: a negative errno style error code
- message: an error message

### Core::RemoveId (Opcode 4)

This event is used internally by the object ID management logic. When a client deletes an object, the server will send this event to acknowledge that it has seen the delete request. When the client receives this event, it will know that it can safely reuse the object ID.

Struct(
Int: id
)

- id: a proxy id that was removed

### Core::BoundId (Opcode 5)

This event is emitted when a local object ID is bound to a global ID. It is emitted before the global becomes visible in the registry. This event is deprecated, the BoundProps event should be used because it also contains extra properties.

Struct(
Int: id
Int: global_id
)

- id: a proxy id
- global_id: the global_id as it will appear in the registry.

### Core::AddMem (Opcode 6)

Memory is given to a client as fd of a certain memory type. Further references to this fd will be made with the per memory unique identifier id.

Struct(
Int: id
Id: type
Fd: fd
Int: flags
)

- id: a server allocated id for this memory
- type: the memory type, see enum spa_data_type
- fd: the index of the fd sent with this message
- flags: extra flags

### Core::RemoveMem (Opcode 7)

Remove memory for a client with the given id

Struct(
Int: id
)

- id: the id of the memory to remove. This is the Id from AddMem.

### Core::BoundProps (Opcode 8)

This event is emitted when a local object ID is bound to a global ID. It is emitted before the global becomes visible in the registry.

Struct(
Int: id
Int: global_id
Struct(
Int: n_items
(String: key
String: value)*
): props
)

- id: a proxy id
- global_id: the global_id as it will appear in the registry.
- props: the properties of the global

# Registry proxy/resource

The registry is obtained with the GetRegistry method on the Core object. The Id depends on the new_id that was provided.

## Registry Methods

### Registry::Bind (Opcode 1)

Bind to the global object with id and use the client proxy with new_id as the proxy. After this call, methods can be send to the remote global object and events can be received.

Struct(
Int: id
String: type
Int: version
Int: new_id
)

- id: the global_id to bind to
- type: the type of the global id
- version: the client version of the interface for type
- new_id: the client proxy id for the global object

### Registry::Destroy (Opcode 2)

Try to destroy the global object with id. This might fail when the client does not have permission.

Struct(
Int: id
)

- id: the global id to destroy.

## Registry Events

### Registry::Global (Opcode 0)

Notify a client about a new global object.

Struct(
Int: id
Int: permissions
String: type
Int: version
Struct(
Int: n_items
(String: key
String: value)*
): props
)

- id: the global id
- permissions: permission bits
- type: the type of object
- version: the server version of the object
- props: extra global properties

### Registry::GlobalRemove (Opcode 1)

A global with id was removed

Struct(
Int: id
)

- id: the global id that was removed.

# PipeWire:Interface:Client

The client object represents a client connect to the PipeWire server. Permissions of the client can be managed.

The currently connected client always has the Client object with proxy id 1.

## Client Methods

### Client::Error (Opcode 1)

Is used to send an error to a client.

Struct(
Int: id
Int: res
String: error
)

- id: a client proxy id to send the error to
- res: a negative errno style error code
- error: an error message

### Client::UpdateProperties (Opcode 2)

Is used to update the properties of a client.

Struct(
Struct(
Int: n_items
(String: key
String: value)*
): props
)

- props: properties to update on the client.

### Client::GetPermissions (Opcode 3)

Get the currently configured permissions on the client.

Struct(
Int: index
Int: num
)

- index: the start index of the permissions to get
- num: the number of permissions to get

This method will result in at most num Permission Events.

### Client::UpdatePermissions (Opcode 4)

Update the permissions of the global objects using the provided array with permissions

Struct(
Int: n_permissions
( Int: id
Int: permission
)*
)

- n_permissions: number of permissions
- id: the global id
- permissions: the permissions for the global id

## Client Events

### Client::Info (Opcode 0)

Get client information updates. This is emitted when binding to a client or when the client info is updated later.

Struct(
Int: id
Long: change_mask
Struct(
Int: n_items
(String: key
String: value)*
): props
)

- id: the global id of the client
- change_mask: the changes emitted by this event
- props: properties of this object, valid when change_mask has (1<<0)

### Client::Permissions (Opcode 1)

Emitted as the reply of the GetPermissions method.

Struct(
Int: index
Struct(
Int: n_permissions
(Int: id
Int: permission)*
)
)

- index: index of the first permission
- n_permissions: the number of permission entries
- id: the global id of the object
- permissions: the permission for the given id

# PipeWire:Interface:Device

A device is an object that manages other devices or nodes.

The usual flow is to bind to the Device object. This will result in an Info event. From the Info event one can find the available params to enumerate.

## Device methods

### Device::SubscribeParams (Opcode 1)

Automatically emit Param events for the given ids when they are changed.

Struct(
Array[Id]: ids
)

- ids: and array of param Id to subscribe to

### Device::EnumParams (Opcode 2)

Enumerate the values of a param. This will result in Param events.

Struct(
Int: seq
Id: id
Int: index
Int: num
Pod: filter
)

- seq: an automatically generated sequence number, will be copied into the reply
- id: the param id to enumerate.
- index: the first param index to retrieve
- num: the number of params to retrieve
- filter: an optional filter object for the param.

### Device::SetParam (Opcode 3)

Set a parameter on the Device.

Struct(
Id: id
Int: flags
Pod: param
)

- id: the param id to set.
- flags: extra flags
- param: the param object to set

## Device events

### Device::Info (Opcode 0)

The info event is emitted when binding or when the device information changed.

Struct(
Int: id
Long: change_mask
Struct(
Int: n_items
( String: key
String: value )*
): props
Struct(
Int: n_params
( Int: id
Int: flags )*
): param_info
)

- id: the id of the global
- change_mask: a bitmask of changed fields
- props: extra properties, valid when change_mask is (1<<0)
- param_info: info about the parameters, valid when change_mask is (1<<1) For each parameter, the id and current flags are given.
  - param_info.id : see enum spa_param_type
  - param_info.flags: struct spa_param_info.flags

### Device::Param (Opcode 1)

Emitted as a result of EnumParams or SubscribeParams.

Struct(
Int: seq
Id: id
Int: index
Int: next
Pod: param
)

- seq: the sequence number send by the client EnumParams or server generated in the SubscribeParams case.
- id: the param id that is reported, see enum spa_param_type
- index: the index of the parameter
- next: the index of the next parameter
- param: the parameter. The object type depends on the id

# PipeWire:Interface:Factory

A factory is an object that allows one to create new objects.

## Factory methods

A factory has no methods

## Factory events

### Factory::Info (Opcode 0)

Info is emitted when binding to the factory global or when the information changed.

Struct(
Int: id
String: name
String: type
Int: version
Long: change_mask
Struct(
Int: n_items
( String: key
String: value )*
): props
)

- id: the global id of the factory
- name: the name of the factory. This can be used as the name for Core::CreateObject
- type: the object type produced by this factory
- version: the version of the object interface
- change_mask: bitfield of changed values.
- props: optional properties of the factory, valid when change_mask is (1<<0)

# PipeWire:Interface:Link

A link is a connection between 2 ports.

## Link methods

A link has no methods

## Link events

### Link::Info (Opcode 0)

Info is emitted when binding to the link global or when the information changed.

Struct(
Int: id
Int: output_node_id
Int: output_port_id
Int: input_node_id
Int: input_port_id
Long: change_mask
Int: state
String: error
Pod: format
Struct(
Int: n_items
( String: key
String: value )*
): props
)

- id: the global id of the link
- output_node_id: the global id of the output node
- output_port_id: the global id of the output port
- input_node_id: the global id of the input node
- input_port_id: the global id of the input port
- change_mask: bitfield of changed values.
- state: the state of the link, valid when change_mask has (1<<0)
  - see enum pw_link_state for values
- error: an optional error string
- format: an optional format for the link, valid when change_mask has (1<<1)
- props: optional properties of the link, valid when change_mask is (1<<2)

# PipeWire:Interface:Module

A Module provides dynamically loaded functionality

## Module methods

A module has no methods

## Module events

### Module::Info (Opcode 0)

Info is emitted when binding to the module global or when the information changed.

Struct(
Int: id
String: name
String: filename
String: args
Long: change_mask
Struct(
Int: n_items
( String: key
String: value )*
): props
)
args
uint32_t int int const char va_list args
Definition core.h:434

- id: the global id of the module
- name: the name of the module
- filename: the filename of the module
- args: arguments passed when loading the module
- change_mask: bitfield of changed values.
- props: optional properties of the module, valid when change_mask has (1<<0)

# PipeWire:Interface:Node

A Node is a processing element in the graph

## Node methods

### Node::SubscribeParams (Opcode 1)

Automatically emit Param events for the given ids when they are changed.

Struct(
Array[Id]: ids
)

- ids: and array of param Id to subscribe to

### Node::EnumParams (Opcode 2)

Enumerate the values of a param. This will result in Param events.

Struct(
Int: seq
Id: id
Int: index
Int: num
Pod: filter
)

- seq: an automatically generated sequence number, will be copied into the reply
- id: the param id to enumerate.
- index: the first param index to retrieve
- num: the number of params to retrieve
- filter: an optional filter object for the param.

### Node::SetParam (Opcode 3)

Set a parameter on the Node.

Struct(
Id: id
Int: flags
Pod: param
)

- id: the param id to set.
- flags: extra flags
- param: the param object to set

### Node::SendCommand (Opcode 4)

Send a Command to the node.

Struct(
Pod: command
)

- command: the command to send. See enum spa_node_command

## Node events

### Node::Info (Opcode 0)

The info event is emitted when binding or when the node information changed.

Struct(
Int: id
Int: max_input_ports
Int: max_output_ports
Long: change_mask
Int: n_input_ports
Int: n_output_ports
Id: state
String: error
Struct(
Int: n_items
( String: key
String: value )*
): props
Struct(
Int: n_params
( Int: id
Int: flags )*
): param_info
)

- id: the id of the node global
- max_input_port: the maximum input ports for the node
- max_output_port: the maximum output ports for the node
- change_mask: a bitmask of changed fields
- n_input_port: the number of input ports, when change_mask has (1<<0)
- n_output_port: the number of output ports, when change_mask has (1<<1)
- state: the current node state, when change_mask has (1<<2)
  - See enum pw_node_state for values
- error: an error message.
- props: extra properties, valid when change_mask is (1<<3)
- param_info: info about the parameters, valid when change_mask is (1<<4) For each parameter, the id and current flags are given.
  - param_info.id : see enum spa_param_type
  - param_info.flags: struct spa_param_info.flags

### Node::Param (Opcode 1)

Emitted as a result of EnumParams or SubscribeParams.

Struct(
Int: seq
Id: id
Int: index
Int: next
Pod: param
)

- seq: the sequence number send by the client EnumParams or server generated in the SubscribeParams case.
- id: the param id that is reported, see enum spa_param_type
- index: the index of the parameter
- next: the index of the next parameter
- param: the parameter. The object type depends on the id

# PipeWire:Interface:Port

A port is part of a node and allows links with other ports.

## Port methods

### Port::SubscribeParams (Opcode 1)

Automatically emit Param events for the given ids when they are changed.

Struct(
Array[Id]: ids
)

- ids: and array of param Id to subscribe to

### Port::EnumParams (Opcode 2)

Enumerate the values of a param. This will result in Param events.

Struct(
Int: seq
Id: id
Int: index
Int: num
Pod: filter
)

- seq: an automatically generated sequence number, will be copied into the reply
- id: the param id to enumerate.
- index: the first param index to retrieve
- num: the number of params to retrieve
- filter: an optional filter object for the param.

## Port events

### Port::Info (Opcode 0)

The info event is emitted when binding or when the port information changed.

Struct(
Int: id
Int: direction
Long: change_mask
Struct(
Int: n_items
( String: key
String: value )*
): props
Struct(
Int: n_params
( Int: id
Int: flags )*
): param_info
)

- id: the id of the port global
- direction: the direction of the port, see enum pw_direction
- change_mask: a bitmask of changed fields
- props: extra properties, valid when change_mask is (1<<0)
- param_info: info about the parameters, valid when change_mask is (1<<1) For each parameter, the id and current flags are given.
  - param_info.id : see enum spa_param_type
  - param_info.flags: struct spa_param_info.flags

### Port::Param (Opcode 1)

Emitted as a result of EnumParams or SubscribeParams.

Struct(
Int: seq
Id: id
Int: index
Int: next
Pod: param
)

- seq: the sequence number send by the client EnumParams or server generated in the SubscribeParams case.
- id: the param id that is reported, see enum spa_param_type
- index: the index of the parameter
- next: the index of the next parameter

# PipeWire:Interface:ClientNode

The ClientNode object is created from the `client-node` factory that is provided by the `libpipewire-module-client-node` module.

It creates a server Node that can be controlled from a client. Processing will happen in the client. It is used by pw-stream and pw-filter to implement the PipeWire media processing nodes.

## ClientNode methods

### ClientNode::GetNode (Opcode 1)

Get the node object associated with the client-node. This binds to the server side Node object.

Struct(
Int: version
Int: new_id
)

- version: the Node version to bind as
- new_id: the proxy id

### ClientNode::Update (Opcode 2)

Update the params and info of the node.

Struct(
Int: change_mask
Int: n_params
( Pod: param )*
Struct(
Int: max_input_ports
Int: max_output_ports
Long: change_mask
Long: flags
Int: n_items
( String: key
String: value )*
Int: n_params
( Id: id
Int: flags )*
): info
)

- change_mask: a bitfield of changed items
- n_params: number of update params, valid when change_mask has (1<<0)
- param: an updated param
- info: an updated `struct spa_node_info`, valid when change_mask has (1<<1)
  - max_input_ports: maximum input ports
  - max_output_ports: maximum output ports
  - change_mask: bitmask of changed items
  - flags: flags, see `struct spa_node_info`, when change_mask has (1<<0)
  - n_items: updated properties, valid when info.change_mask has (1<<1)
  - n_params: updated `struct spa_param_info`, valid when info.change_mask has (1<<2)

### ClientNode::PortUpdate (Opcode 3)

Create, Update or destroy a node port.

When the port is not known on the server, the port is created. When info is None, the port is destroyed. Otherwise, the port information is updated.

Struct(
Int: direction
Int: port_id
Int: change_mask
Int: n_params
( Pod: param )*
Struct(
Long: change_mask
Long: flags
Int: rate_num
Int: rate_denom
Int: n_items
( String: key
String: value )*
Int: n_params
( Id: id
Int: flags )*
): info
)

- direction: the port direction
- port_id: the port id
- change_mask: a bitfield of changed items
- n_params: number of updated params, valid when change_mask has (1<<0)
- param: n_params updated params
- info: an updated `struct spa_port_info`, valid when change_mask has (1<<1)
  - change_mask: bitmask of changed items
  - flags: flags, see `struct spa_port_info`, when change_mask has (1<<0)
  - rate_num: updated rate numerator
  - rate_denom: updated rate denominator, when info.change_mask has (1<<1)
  - n_items: updated properties, valid when info.change_mask has (1<<2)
  - n_params: updated `struct spa_param_info`, valid when info.change_mask has (1<<3)

### ClientNode::SetActive (Opcode 4)

Set the node active or inactive.

Struct(
Bool: active
)

- active: the new state of the node

### ClientNode::Event (Opcode 5)

Emit an event on the node.

Struct(
Pod: event
)

- event: the event to emit. See `enum spa_node_event`.

### ClientNode::PortBuffers (Opcode 6)

This method is used by the client when it has allocated buffers for a port. It is usually called right after the UseBuffers event to let the server know about the the newly allocated buffer memory.

Struct(
Int: direction
Int: port_id
Int: mix_id
Int: n_buffers
( Int: n_datas
( Id: type
Fd: memfd
Int: flags
Int: mapoffset
Int: maxsize
)*
)*
)

- direction: the direction of the port
- port_id: the port id
- mix_id: the mix id of the port
- n_buffer: the number of buffers
- n_data: for each buffer the number of data planes
- type: the plane memory type
- memfd: the plane memfd
- mapoffset: the start offset of where the buffer memory starts
- maxsize: the maximum size of the memory.

## ClientNode events

### ClientNode::Transport (Opcode 0)

The server will allocate the activation record and eventfd for the node and transfer this to the client with the Transport event.

Struct(
Fd: readfd
Fd: writefd
Int: memfd
Int: offset
Int: size
)

- readfd: the eventfd to start processing
- writefd: the eventfd to signal when the driver completes and profiling is enabled.
- memfd: the index of the memfd of the activation record
- offset: the offset in memfd of the start of the activation record
- size: the size of the activation record

The activation record is currently an internal data structure that is not yet ABI stable.

The writefd is meant to wake up the server after the driver completes so that the profiler can collect the information. The profiler is active when the pw_node_activation::flags fields has PW_NODE_ACTIVATION_FLAG_PROFILER set. When the profiler is disabled (or when the node is not driving), this eventfd should not be signaled.

### ClientNode::SetParam (Opcode 1)

Set a parameter on the Node.

Struct(
Id: id
Int: flags
Pod: param
)

- id: the param id to set.
- flags: extra flags
- param: the param object to set

### ClientNode::SetIO (Opcode 2)

Set an IO area on the node.

Struct(
Id: id
Int: memid
Int: offset
Int: size
)

- id: the io area id to set.
- the memid to use, this is signaled with Core::AddMem
- offset: the start offset in the memory area
- the size of the io area

### ClientNode::Event (Opcode 3)

Emit an event on the node.

Struct(
Pod: event
)

- event: the event to emit. See `enum spa_node_event`.

### ClientNode::Command (Opcode 4)

Send a command on the node.

Struct(
Pod: command
)

- command: the command to send. See `enum spa_node_command`.

### ClientNode::AddPort (Opcode 5)

Add a new port to the node

Struct(
Int: direction
Int: port_id
Struct(
Int: n_items
( String: key
String: value )*
): props
)

- direction: the direction of the new port
- port_id: the port id of the new port
- props: optional extra properties for the port

### ClientNode::RemovePort (Opcode 6)

Remove a port from the node

Struct(
Int: direction
Int: port_id
)

- direction: the direction of the port to remove
- port_id: the port id of the port to remove

### ClientNode::PortSetParam (Opcode 7)

Set a parameter on the Port of the node.

Struct(
Int: direction
Int: port_id
Id: id
Int: flags
Pod: param
)

- direction: the direction of the port
- port_id: the port id of the port
- id: the param id to set.
- flags: extra flags
- param: the param object to set

### ClientNode::UseBuffers (Opcode 8)

Use a set of buffers on the mixer port

Struct(
Int: direction
Int: port_id
Int: mix_id
Int: flags
Int: n_buffers
( Int: memid
Int: offset
Int: size
Int: n_metas
( Id: type
Int: size
)*: meta
Int: n_datas
( Id: type
Int: data
Int: flags
Int: mapoffset
Int: maxsize
)*: data
)*: buffer
)

- direction: the direction of the port
- port_id: the port id of the port
- mix_id: the mixer id of the port
- flags: extra flags
- id: the param id to set.
- flags: extra flags
  - SPA_NODE_BUFFERS_FLAG_ALLOC (1<<0) to let the client allocate buffers, in which case the PortBuffers method needs to be called with the allocated buffer memory.
- n_buffers: the number of buffers
- memid: the memory id of the buffer metadata and or data
- offset: the offset in memid of the buffer
- size: the size of the buffer metadata or data
- n_metas: number of metadata. The buffer memory first contains this number of metadata parts of the given type and size
  - type: metadata type
  - size: metadata size, round up with 8 to get to the next metadata
- n_data: the number of datablocks (planes) per buffer
  - type: the data type, this can be:
    - SPA_DATA_MemId to reference a memfd from Core:AddMem
    - SPA_DATA_MemPtr to reference this buffer memid
  - data: contains the memid or offset in the memid
  - flags: extra flags for the data
  - mapoffset: the offset in memfd
  - maxsize: the maxsize of the memory in memfd

### ClientNode::PortSetIO (Opcode 9)

Set an IO area on a mixer port.

Struct(
Int: direction
Int: port_id
Int: mix_id
Id: id
Int: memid
Int: offset
Int: size
)

- direction: the direction of the port
- port_id: the port id of the port
- mix_id: the mix id of the port
- id: the IO area to set. See enum spa_io_type
- memid: the memid of the io area, added with Core::AddMem
- offset: the offset in the memid
- size: the size of the IO area

### ClientNode::SetActivation (Opcode 10)

Notify the client of the activation record of a peer node. This activation record should be triggered when this node finishes processing.

Struct(
Int: node_id
Fd: signalfd
Int: memid
Int: offset
Int: size
)

- node_id: the node_id of the peer node
- signalfd: the eventfd of the peer node
- memid: the memid of the activation record of the peer from Core:AddMem
- offset: the offset in memid
- size: the size of the activation record

### ClientNode::PortSetMixInfo (Opcode 11)

Notify the node of the peer of a mixer port. This can be used to track the peer ports of a node.

Struct(
Int: direction
Int: port_id
Int: mix_id
Int: peer_id
Struct(
Int: n_items
( String: key
String: value )*
): props
)

- direction: the direction of the port
- port_id: the port id of the port
- mix_id: the mix id of the port
- peer_id: the id of the peer port
- props: optional properties

# PipeWire:Interface:Metadata

Metadata is a shared database of settings and properties.

## Metadata methods

### Metadata::SetProperty (Opcode 1)

Set a property in the metadata store.

Struct(
Int: subject
String: key
String: type
String: value
)

- subject: the id of the object, this needs to be a valid global_id
- key: a key
- type: an optional type
- value: a value

### Metadata::Clear (Opcode 2)

Clear the metadata store.

Struct(
None
)

## Metadata events

### Metadata::Property (Opcode 0)

A metadata key changed. This is also emitted when binding to the metadata.

Struct(
Int: subject
String: key
String: type
String: value
)

- subject: the id of the object, this is a valid global_id
- key: a key
- type: an optional type
- value: a value

# PipeWire:Interface:Profiler

The profiler object allows one to receive profiler information of the pipewire graph.

## Profiler methods

The profiler has no methods

## Profiler events

### Profiler::Profile (Opcode 0)

Struct(
Pod: object
)

- object: a SPA_TYPE_OBJECT_Profiler object. See enum spa_profiler

# Footer

The message footer contains additional messages, not directed to the destination object defined by the `Id` field.

The footer consists of a single POD, immediately following the payload POD. The footer POD consists of a sequence of footer opcode Ids and footer payload Structs containing their arguments:

Struct(
Id: opcode1,
Struct { ... },
Id: opcode2,
Struct { ... },
...
)

The footer opcodes are separate for server-to-client (`core`) and client-to-server (`client`) directions.

The message footer is processed before other parts of the message, including the object Id lookup.

## Core Generation (Footer Opcode 0)

Struct(
Long: registry_generation,
)

Indicates to the client what is the current registry generation number of the Context on the server side.

The server shall include this footer in the next message it sends that follows the increment of the registry generation number.

See also
  Registry generation

## Client Generation (Footer Opcode 0)

Struct(
Long: client_generation,
)

Indicates to the server what is the last registry generation number the client has processed.

The client shall include this footer in the next message it sends, after it has processed an incoming message whose footer includes a registry generation update.

See also
  Registry generation

# Registry generation

The registry generation is a 64-bit integer in the PipeWire server Context that increments by one when the server allocates a new global PW_KEY_OBJECT_ID for an object.

The server keeps track of each global id as a tuple ( id, object generation ) where object generation is the registry generation value when the id was allocated.

When an object is destroyed, its id value may be reallocated to a different object. Because the protocol is asynchronous, the object id alone is not sufficient to uniquely identify objects.

The server looks up objects based on a tuple ( id, generation ) as follows:

1. Look up the Global based on the id.
2. The lookup fails if there is no global for the id, or if generation < object generation.

The protocol message generally contains only the object id. The registry generation part is passed around as follows:

1. The server sends the current registry generation to clients in the protocol footer, if it has changed.
2. The clients keep track of the latest registry generation of the messages they have processed. This is the client generation.
3. Each client sends their client generation in the protocol footer of the next message to the server, if its value has changed.
4. The server keeps track for each client the client generation they have sent back.
5. In each protocol message received from client, the server considers each object id as tuple ( id, client generation ).

This allows the server to know if the object id the client refers to was already destroyed, but the client has not yet processed the message indicating that the id is gone. The server indicates failed lookups of this type with error code ESTALE to the client.

If a client has not sent any client generation updates to the server, then the server will not do any registry generation checks in object lookups. This is for backward compatibility only.

The registry generation is an internal detail of the server implementation and the native protocol, and is not visible to clients in the PipeWire API. To identify objects uniquely, clients can use PW_KEY_OBJECT_SERIAL, which are unique for objects and not reused, unlike PW_KEY_OBJECT_ID

See also
  PW_KEY_OBJECT_SERIAL