Subject: Format of NPT

From: "Y. Matsui" <[email-masked]>
Date: Tue, 10 Jul 2001 16:41:22 +0900

Dear all,

I have just subcsribed to this reflector, so that I don't see
if my following question has been discussed and concluded here.

I think there is an inconsistency between the definition and
example usages about the format of NPT.

In Section 12.29 of RFC2326 (RTSP), Range is defined as follows:

   Range            = "Range" ":" 1\#ranges-specifier
                          [ ";" "time" "=" utc-time ]
   ranges-specifier = npt-range | utc-range | smpte-range

In Section 3.6 of RFC2326 (RTSP), npt-range is defined as follows:

   npt-range    =   ( npt-time "-" [ npt-time ] ) | ( "-" npt-time )

Thus, the range specifier such as "npt" is not present.

Examples in this section are the following:

     npt=123.45-125
     npt=12:05:35.3-

And the excerpt from Annex C.1.5:

   The "a=range" attribute defines the total time range of the stored
   session. (The length of live sessions can be deduced from the "t" and
   "r" parameters.) Unless the presentation contains media streams of
   different durations, the range attribute is a session-level
   attribute. The unit is specified first, followed by the value range.
   The units and their values are as defined in Section 3.5, 3.6 and 3.7.

   Examples:
     a=range:npt=0-34.4368
     a=range:clock=19971113T2115-19971113T2203

It seems that the range specifier "npt" is expected in example usages.
If so, the definition of npt-range must be:
  npt-range = "npt" "=" ( npt-time "-" [ npt-time ] ) | ( "-" npt-time )

I would like to know which is correct. Any comments are appreciated.

Best regards,
Yoshinori Matsui
Matsushita/Panasonic