2.2.1.1 ASF Payload Extension System Extension

The RTP Payload Format for WMA and WMV [WMRTP] defines a field called Extension. This field can contain extensions to the RTP Payload Format. The Microsoft Extensions to the DLNA Guidelines define an extension for use in the Extension field called the ASF Payload Extension System extension.

The ASF Payload Extension System extension allows any ASF Payload Extensions System data [ASF] that can be present in an ASF file to be transmitted to the RTP receiver.

When the ASF Payload Extension System extension is used, the fields in the Extension field (see [WMRTP] section 3.6.3) MUST be set as follows.

The value of the Extension Type field MUST be set to 0x04.

The value of the Extension Length field MUST be set to the size of the Extension Data field, in bytes. The valid range for this field is 0x00 to 0xFF, inclusive.

The value of the Extension Data field MUST be set to the ASF Payload Extension System data. If the stream has multiple ASF Payload Extension Systems, then the data for each of the ASF Payload Extension Systems MUST be concatenated in the same order as the ASF Payload Extension Systems are listed in the SDP.

For details about how to list ASF Payload Extension Systems in the SDP, see section 2.2.2.4.