The Media Kit: Message Formats

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# 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.

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