On Wed, 2 Nov 2011 11:58:04 +0100, Daniel Glöckner <daniel-gl@xxxxxxx> wrote: >> Converting between the two can be done when making the timestamp but it's >> non-trivial at other times and likely isn't supported. I could be wrong, >> though. This might lead to e.g. timestamps that are taken before >> switching >> to summer time and for which the conversion is done after the switch. >> This might be a theoretical possibility, but there might be also >> unfavourable interaction with the NTP. > > Summertime/wintertime is purely a userspace thing. UTC as returned by > gettimeofday is unaffected by that. Right, DST is a non-issue. > NTP AFAIK adjusts the speed of the monotonic clock, so there is a constant > delta between wall clock time and clock monotonic For NTP it depends. Simple NTP, as in ntpdate, warps the wall clock. Full-blown NTP only adjusts the speed. > unless there is a leap > second or someone calls settimeofday. Applications currently using the > wall clock timestamps should have trouble dealing with that as well. I can think of at least three other sources of wall clock time, that could trigger a warp: - GPS receiver (TAI), - cellular modem (NITZ), - and, of course, manual setting. So if at all possible I'd much prefer monotonic over real timestamps. -- Rémi Denis-Courmont http://www.remlab.net/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
