Standards Track A. Rao Netscap - RFC Editor

RFC 2326 Real Time Streaming Protocol April 1998The path components of the RTSP URL are opaque to the client and donot imply any particular file system structure for the server.This decoupling also allows presentation descriptions to be usedwith non-RTSP media control protocols simply by replacing thescheme in the URL.3.3 Conference IdentifiersConference identifiers are opaque to RTSP and are encoded usingstandard URI encoding methods (i.e., LWS is escaped with %). They cancontain any octet value. The conference identifier MUST be globallyunique. For H.323, the conferenceID value is to be used.conference-id =1*xcharConference identifiers are used to allow RTSP sessions to obtainparameters from multimedia conferences the media server isparticipating in. These conferences are created by protocolsoutside the scope of this specification, e.g., H.323 [13] or SIP[12]. Instead of the RTSP client explicitly providing transportinformation, for example, it asks the media server to use thevalues in the conference description instead.3.4 Session IdentifiersSession identifiers are opaque strings of arbitrary length. Linearwhite space must be URL-escaped. A session identifier MUST be chosenrandomly and MUST be at least eight octets long to make guessing itmore difficult. (See Section 16.)session-id = 1*( ALPHA | DIGIT | safe )3.5 SMPTE Relative TimestampsA SMPTE relative timestamp expresses time relative to the start ofthe clip. Relative timestamps are expressed as SMPTE time codes forframe-level access accuracy. The time code has the formathours:minutes:seconds:frames.subframes, with the origin at the startof the clip. The default smpte format is "SMPTE 30 drop" format, withframe rate is 29.97 frames per second. Other SMPTE codes MAY besupported (such as "SMPTE 25") through the use of alternative use of"smpte time". For the "frames" field in the time value can assumethe values 0 through 29. The difference between 30 and 29.97 framesper second is handled by dropping the first two frame indices (values00 and 01) of every minute, except every tenth minute. If the framevalue is zero, it may be omitted. Subframes are measured inone-hundredth of a frame.Schulzrinne, et. al. Standards Track [Page 16]