2.2.5.2.5 Stream Number Attribute ("a=stream")

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The stream attribute MUST be present for each media description. It MUST specify the ASF stream number that the media description refers to. The stream number specified by the stream attribute MUST be the same number that is specified for the stream in the ASF Stream Properties object in the ASF file header.

If the media description does not correspond to a stream in the ASF content because it is a retransmission stream or an FEC stream, the stream number specified by the stream attribute MUST be chosen according to the following table to correctly indicate if the media description is for a retransmission stream or an FEC stream. If there are multiple media descriptions of the same type, each MUST specify a different stream number.

 Stream-num

 Meaning

1-65534

Media description is for an ASF stream.

65536-131070

Media description is for a retransmission stream.

The ABNF syntax for this attribute is as follows:

 stream-num          = "a=stream:" 1*10DIGIT

A stream number that is not within the preceding ranges is invalid.