9. SDP Grammar (SDP语法)

本节提供SDP的增强巴科斯-诺尔范式 (Augmented BNF, ABNF) 语法。ABNF在[RFC 5234]中定义。

SDP语法定义

; SDP Syntax
session-description = proto-version
                      origin-field
                      session-name-field
                      information-field
                      uri-field
                      email-fields
                      phone-fields
                      connection-field
                      bandwidth-fields
                      time-fields
                      key-field
                      attribute-fields
                      media-descriptions

proto-version =       %x76 "=" 1*DIGIT CRLF
                      ;this memo describes version 0

origin-field =        %x6f "=" username SP sess-id SP sess-version SP
                      nettype SP addrtype SP unicast-address CRLF

session-name-field =  %x73 "=" text CRLF

information-field =   [%x69 "=" text CRLF]

uri-field =           [%x75 "=" uri CRLF]

email-fields =        *(%x65 "=" email-address CRLF)

phone-fields =        *(%x70 "=" phone-number CRLF)

connection-field =    [%x63 "=" nettype SP addrtype SP
                      connection-address CRLF]

bandwidth-fields =    *(%x62 "=" bwtype ":" bandwidth CRLF)

time-fields =         1*( %x74 "=" start-time SP stop-time
                      *(CRLF repeat-fields) CRLF)
                      [zone-adjustments CRLF]

repeat-fields =       %x72 "=" repeat-interval SP typed-time
                      1*(SP typed-time)

zone-adjustments =    %x7a "=" time SP ["-"] typed-time
                      *(SP time SP ["-"] typed-time)

key-field =           [%x6b "=" key-type CRLF]

attribute-fields =    *(%x61 "=" attribute CRLF)

media-descriptions =  *( media-field
                      information-field
                      *connection-field
                      bandwidth-fields
                      key-field
                      attribute-fields )

media-field =         %x6d "=" media SP port ["/" integer]
                      SP proto 1*(SP fmt) CRLF

; Sub-rules
username =            non-ws-string
sess-id =             1*DIGIT
sess-version =        1*DIGIT
nettype =             token
addrtype =            token
media =               token
port =                1*DIGIT
proto =               token *("/" token)
fmt =                 token

注意: 完整的ABNF语法定义非常详细，包括所有字段的详细规则和终端符号定义。完整语法请参考 RFC 4566官方文档第9节。

SDP语法定义​

SDP语法定义