Message Formats

The Media Kit has a number of message formats. The following table lists the messages (by their 'what' constants) and describes their intents. The subsequent sections list the fields that are contained in the messages.

Notification Messages

Declared in: be/media/MediaDefs.h

Constant	Meaning
B_MEDIA_WILDCARD	Used to match any notification (used only in calls to StartWatching() and StopWatch ing() ).
B_MEDIA_NODE_CREATED	A new node has been created
B_MEDIA_NODE_DELETED	Not sent in R4.5.
B_MEDIA_CONNECTION_MADE	Not sent in R4.5.
B_MEDIA_CONNECTION_BROKEN	Not sent in R4.5.
B_MEDIA_BUFFER_CREATED	Not sent in R4.5.
B_MEDIA_BUFFER_DELETED	Not sent in R4.5.
B_MEDIA_TRANSPORT_STATE	Not sent in R4.5.
B_MEDIA_PARAMETER_CHANGED	Indicates that a parameter in a BParameterWeb has changed.
B_MEDIA_FORMAT_CHANGED	Not sent in R4.5.
B_MEDIA_WEB_CHANGED	Indicates that a node's BParameterWeb has changed.
B_MEDIA_DEFAULT_CHANGED	Not sent in R4.5.
B_MEDIA_NEW_PARAMTER_VALUE	Indicates that a parameter in a BParameterWeb has changed. Unlike the B_MEDIA_PARAMETER_CHANGED notification, this includes the new value.
B_MEDIA_NODE_STOPPED	Indicates that a node has stopped.
B_MEDIA_FLAVORS_CHANGED	Indicates that flavors have changed.

Messages with these 'what' are sent by the media server to any application that's registered to receive notifications by calling BMediaRoster::StartWatching().

The B_MEDIA_TRANSPORT_STATE message isn't sent in BeOS R4.

B_MEDIA_NODE_CREATED , B_MEDIA_NODE_DELETED

Field	Type Code	Description
"be:media_node_id"	B_INT32_TYPE	The ID of the media_node that was created or deleted.

B_MEDIA_CONNECTION_MADE

The B_MEDIA_CONNECTION_MADE message has three data fields:

Field	Type Code	Description
"be:output"	B_RAW_TYPE	A media_output structure describing the connection's output.
"be:input"	B_RAW_TYPE	A media_input structure describing the connection's input.
"be:format"	B_RAW_TYPE	A media_format structure describing the format of the data that flows across the connection.

B_MEDIA_CONNECTION_BROKEN

Field	Type Code	Description
"destination"	B_RAW_TYPE	A media_destination structure describing the destination of the connection that's been broken.
"source"	B_RAW_TYPE	A media_source structure describing the source of the connection that's been broken.

B_MEDIA_BUFFER_CREATED

Field	Type Code	Description
"clone_info"	B_RAW_TYPE	An area_info structure describing the buffer's location in memory. This is an array, one entry per buffer created.

B_MEDIA_BUFFER_DELETED

Field	Type Code	Description
"be:media_buffer_id"	B_INT32_TYPE	The buffer ID number of the buffer being deleted. This is an array, one entry per buffer deleted.

B_MEDIA_FORMAT_CHANGED

Field	Type Code	Description
"be:source"	B_RAW_TYPE	A media_source structure describing the source of the connection whose format changed.
"be:destination"	B_RAW_TYPE	A media_source structure describing the source of the connection whose format changed.
"be:format"	B_RAW_TYPE	A media_format structure describing the new format.

B_MEDIA_PARAMETER_CHANGED

Field	Type Code	Description
"be:node"	B_RAW_TYPE	A media_node structure indicating which node's parameter web has changed.
"be:parameter"	B_INT32_TYPE	The ID number of the parameter whose value has changed.

B_MEDIA_WEB_CHANGED

Field	Type Code	Description
"node"	B_RAW_TYPE	A media_node structure indicating which node's parameter web has changed.

B_MEDIA_NEW_PARAMETER_VALUE

Field	Type Code	Description
"node"	B_RAW_TYPE	A media_node structure indicating which node is reporting a changed parameter value.
"parameter"	B_INT32_TYPE	The parameter ID of the changed parameter.
"when"	B_INT64_TYPE	The performance time at which the change took effect.
"value"	B_RAW_TYPE	The parameter's new value.

B_MEDIA_FLAVORS_CHANGED

Field	Type Code	Description
"be:addon_id"	B_INT32_TYPE	The add-on ID of the add-on whose flavors have changed
"be:new_count"	B_INT32_TYPE	How many new flavors have been added.
"be:gone_count"	B_INT32_TYPE	How many flavors have been removed.