Re: [AVTCORE] Leap seconds

[Kevin Gross <[e-mail]>]

Well, that would fix things. By my reading, RFC 3550 is not clear on this
however. I'm not sure trying to figure out the original intent of the RFC
will help us resolve things because nowhere in the text do I see any
indications that the RFC authors gave consideration to the NTP leap second
issue.

The RFC does say "Wallclock time (absolute date and time) is represented
using the *timestamp format* of the Network Time Protocol (NTP), which is in
seconds relative to 0h UTC on 1 January 1900." (emphasis on *timestamp
format* mine) Since it doesn't say anything about leap seconds, you could
interpret it as Dave Singer and Colin Perkins have to mean actual seconds
elapsed.

But a couple sentences later there's, "Running NTP may be useful for
synchronizing streams transmitted from separate hosts." Again, no mention of
leap-seconds but here, since we're talking about actual NTP (as opposed to
"NTP timestamp format"), wouldn't you be inclined to assume that leap
seconds are included in timestamps in this suggested implementation?

I have already determined that TAI time is best for my application. If
anyone knows of any existing signaling mechanism I can use to communicate
this to receivers (e.g. specific SDP a= records), I
would welcome suggestions.

Kevin Gross

On Tue, Sep 20, 2011 at 4:21 PM, Colin Perkins <[e-mail]> wrote:

> I guess I'm confused. RTP was intended to use NTP *format* timestamps, but
> intentionally said nothing about synchronisation to any particular time
> source. I don't think it's valid to assume that the NTP format timestamps
> conveyed in RTP are synchronised to UTC, TAI, or anything else, *unless you
> have some explicit signalling to state that*.
>
> Colin
>
>