MPEG 4 Scene Commands

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We will now review the syntax of MPEG-4 scene commands in both BT and XMT-A formats. Please remember that BT and XMT languages are case sensitive.

Command declaration

BT format

RAP AT time IN esID { .... }

RAP and IN esID can be omitted most of the time.

XMT format

<par begin="time" atES_ID="esID" isRAP="yes" > ... </par>

isRAP and atES_ID can be omitted most of the time. isRAP is a GPAC extension.

Replacing a simple field

BT format

REPLACE nodeName.fieldName BY newValue

XMT format

<Replace atNode="nodeName" atField="fieldName" value="newValue" />

Replacing a SFNode field

BT format

REPLACE nodeName.fieldName BY NodeDeclaration {... }

XMT format

<Replace atNode="nodeName" atField="fieldName" >
<NodeXXX />
</Replace>

Note that the new node can be DEF'ed, or that a null node may be specified (NULL ).

Replacing a value in a multiple field

BT format

REPLACE nodeName.fieldName[idx] BY newValue

XMT format

<Replace atNode="nodeName" atField="fieldName" position="idx" value="newValue" />

For XMT-A, idx can also take the special values 'BEGIN' and 'END'. Replacement of a node in an MFNode field is the combination of both syntax

Replacing a multiple field

BT format

REPLACE nodeName.fieldName BY [value1 ... valueN]

REPLACE nodeName.fieldName BY [Node { ... } ... Node { ... }]

XMT format

<Replace atNode="nodeName" atField="fieldName" value="value1 ... valueN" />

<Replace atNode="nodeName" atField="fieldName" >
<NodeXXX>...</NodeXXX>
<NodeXXX>...</NodeXXX>
</Replace>

Replacement of a node in an MFNode field is the combination of both syntax

Deleting a node

BT format

DELETE nodeName

DELETE nodeName.fieldName

XMT format

<Delete atNode="nodeName" />

<Delete atNode="nodeName" atField="fieldName" />

Deleting a value in a multiple field

BT format

DELETE nodeName.fieldName[idx]

XMT format

<Delete atNode="nodeName" atField="fieldName" position="idx" />

For XMT-A, idx can also take the special values 'BEGIN' and 'END'.

Inserting a simple value in a multiple field

BT format

INSERT AT nodeName.fieldName[idx] newValue

APPEND TO nodeName.fieldName newValue

XMT format

<Insert atNode="nodeName" atField="fieldName" position="idx" value="newValue" />

For XMT-A, idx can also take the special values 'BEGIN' and 'END'.

Inserting a node in a node list field

BT format

INSERT AT nodeName.fieldName[idx] Node { }

APPEND TO nodeName.fieldName Node { }

XMT format

<Insert atNode="nodeName" atField="fieldName" position="idx" >
<NodeXXX>...</NodeXXX>
</Insert>

For XMT-A, idx can also take the special values 'BEGIN' and 'END'.

Replacing a route

BT format

REPLACE ROUTE routeName BY nodeName1.fieldName1 TO nodeName2.fieldName2

XMT format

<Replace atRoute="routeName">
<ROUTE fromNode="nodeName1" fromfield="fieldName1" toNode="nodeName2" toField="fieldName2" />
</Replace>

Inserting a route

BT format

INSERT ROUTE nodeName1.fieldName1 TO nodeName2.fieldName2

XMT format

<Insert>
<ROUTE fromNode="nodeName1" fromfield="fieldName1" toNode="nodeName2" toField="fieldName2" />
</Insert>