Subject: [MMUSIC] RTSP: Bug 771638 - a=range in SDP to indicate live media

From: Magnus Westerlund <[email-masked]>
Date: Tue, 14 Oct 2003 19:36:56 +0200

Hi,

The below text is proposed for resolving the the following bug:

http://rtsp.org/bug771638 - a=range in SDP to indicate live media

 From Annex C:

"
Range of Presentation

The ``a=range'' attribute defines the total time range of the
stored session or an individual media. That Live sessions are
non-seekable can also be indicated, while the length of live
sessions can be deduced from the ``t'' and ``r'' parameters.

The attribute is both a session and a media level attribute. For
presentations that contains media streams of the same durations,
the range attribute {\SHOULD} only be used at session-level. In
case of different length the range attribute {\MUST} be given at
media level for all media. If the attribute is present at media
level and session level the media level values {\SHALL} be used.

The unit is specified first, followed by the value range. The
units and their values are as defined in Section \ref{sec:smpte},
\ref{sec:npt} and \ref{sec:clock}. Any open ended range (start-),
i.e. without stop range, is of unspecified duration and {\SHALL}
be considered as non-seekable content unless this property is
overridden.

This attribute is defined in ABNF \cite{rfc2234} as:

a-range-def = "a" "=" "range" ":" ranges-specifier CRLF

Examples:

   a=range:npt=0-34.4368
   a=range:clock=19971113T2115-19971113T2203
   Non seekable stream of unknown duration:
   a=range:npt=0-

"

Any comments should be given before wednesday the 22nd of October.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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