2.2.6.27 X-RTP-Info

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The X-RTP-Info header is sent by servers in the Announce request when predictive stream selection is used. This header is also sent by clients in the Play request when predictive stream selection is used. For more information on predictive stream selection, see section 2.2.6.10.5.

When sent by the server in the Announce request, the X-RTP-Info header specifies what streams the server has selected for the new playlist entry and specifies transport parameters for each stream. When sent by the client in the Play request, the header lists the predicted streams that the client wants to continue to receive. Any streams that the client no longer wants to receive are omitted from the X-RTP-Info header.

The syntax of the X-RTP-Info header is modeled after the syntax of the RTP-Info header, as specified in [RFC2326] section 12.33, but it contains additional syntax elements that are normally found in the Transport (section 2.2.6.11) header.

The syntax of the X-RTP-Info header is as follows:

 parameter    = ";blocksize=" 1*4DIGIT
              | ( ";client_port="
                   port [ "-" port ] )     ; [RFC2326] section 12.39
              | fec-parameters             ; section 2.2.6.8
              | ( "interleaved=" 
                  channel "-" channel )    ; [RFC2326] section 12.39
              | ";mode=PLAY"
              | ";rtptime=" 1*10DIGIT      ; [RFC2326] section 12.33
              | ( ";server_port="
                   port [ "-" port ] )     ; [RFC2326] section 12.39
              | ";seq=" 1*4DIGIT           ; [RFC2326] section 12.33
              | ";ssrc=" 8HEXDIG           ; [RFC2326] section 12.39
              | ( ";thinlevel=" ( "0" | "1" | "2" ) )
              | ( ";transport=RTP/AVP/" ( "UDP" | "TCP" ) )
              | ";unicast"
            
           quoted-stream-url = <">
                               stream-url      ; [RFC2326] section 12.33
                       <">
            
           optq-stream-url =    stream-url    ; [RFC2326] section 12.33
                           | quoted-stream-url   ; required if stream-url contains "," or ";"
            
           X-RTP-Info        = "X-RTP-Info: " 
                              1# ( optq-stream-url
                                   *32parameter )
            
                     

When the X-RTP-Info header is sent in a Play request, any parameter syntax elements MUST NOT be present.

The unicast parameter MUST be specified in the X-RTP-Info header.

The value of the blocksize parameter, if specified, is the maximum size of the RTP packets, in bytes, that the server will send for the new playlist entry described by the SDP in the Announce request.

The numerical value of the thinlevel parameter MUST be set as follows.

 Value

 Meaning

0

All ASF media objects for the stream will be transmitted.

1

Only ASF media objects that are marked as containing key-frame data are to be transmitted.

2

No ASF media objects for the stream will be transmitted.

If the thinlevel parameter is missing from the X-RTP-Info header in an Announce request, a value of 0 MUST be assumed.