Re: [AVTCORE] Leap seconds

I guess there is some ... unclarity.  On the one hand we read that the tickers that count seconds do just that, tick every second, and that leap-second correction is only required if you want to convert these to civil time.  On the other hand we read of this 'stalling' behavior.  

If we stall periodically, then the counters always have {365 or 366 days} * 24 * 60 * 60 seconds per year.  If we don't, some years are +/-1 second if a second was inserted or deleted, and you need to know which years since your zero-point had leap seconds.

On Sep 19, 2011, at 9:01 , Kevin Gross wrote:

> David Singer and I spent some time last week working through this offline. We're using the same sources and coming to different conclusions. We need some help resolving this open question.
> 
> David's position is that the NTP timestamp continues to increment, with the system oscillator, through a leap second. The leap second is not visible in the NTP timestamp but in a higher layer process that converts NTP timestamps to UTC.
> 
> My reading is that the NTP timestamp *is* UTC time and that the clock is paused for 1 second and a new timeline established at the leap second. This behavior will either upset or complicate media systems attempting to reference their playback to the NTP timestamps delivered in RTCP sender reports.
> 
> RFC 3550 (RTP) does not discuss leap seconds.
> 
> RFC 5905 (NTP) describes the mechanism used to convey an upcoming leap second but does not appear to discuss timestamp behavior associated with the leap second.
> 
> The following two references from David Mills (RFC 5905 author) directly discuss leap second behavior:
> http://www.eecis.udel.edu/~mills/leap.html Section 5
> Last section of http://doc.ntp.org/4.1.2/leap.htm
> -- 
> Kevin Gross
> +1-303-447-0517
> Media Network Consultant
> AVA Networks - www.AVAnw.com, www.X192.org
> 
> 
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David Singer
Multimedia and Software Standards, Apple Inc.