On Wednesday 11 November 2009 18:29:52 Sakari Ailus wrote: > Hans Verkuil wrote: > > On Saturday 24 October 2009 23:56:24 Sakari Ailus wrote: > >> Ivan T. Ivanov wrote: > >>> Hi Sakari, > >> Hi, > >> > >>> On Fri, 2009-10-23 at 13:18 +0300, Sakari Ailus wrote: > >> [clip] > >>>> struct v4l2_event { > >>>> __u32 count; > >>>> __u32 type; > >>>> __u32 sequence; > >>>> struct timeval timestamp; > >>> Can we use 'struct timespec' here. This will force actual > >>> implementation to use high-resolution source if possible, > >>> and remove hundreds gettimeofday() in user space, which > >>> should be used for event synchronization, with more > >>> power friendly clock_getres(CLOCK_MONOTONIC). > >> Good point. I originally picked timeval since it was used in > >> v4l2_buffer. The spec tells to use gettimeofday() for system time but > >> clock skewing is causes problems in video encoding. > >> clock_getres(CLOCK_MONOTONIC) is free of clock skewing and thus should > >> be more suitable for this kind of use. > >> > >> I also propose to use timespec instead of timeval. > >> > > > > Hi Sakari, > > > > What is that status of the event API? It is my impression that it is pretty > > much finished. Sakari, can you make a final 2.3 RFC? Then Guru can take over > > and start the implementation. > > Ah. > > One thing that I was still wondering was that are there use cases where > other kind of time stamps might be useful? I guess that when the V4L2 > was designed no-one though of the need for time stamps of different > type. So are there use cases where gettimeofday() style stamps would > still be better?
If you ever need to relate an event to a specific captured frame, then that might well be useful. But I can't think of an actual use case, though. > In that case we might choose to leave it driver's decision to decide > what kind of timestamps to use and in that case application would just > have to know. The alternative would be to use union and a flag telling > what's in there. > Let's go with timespec. If we need to add an event that has to relate to a specific captured frame then it is always possible to add a struct timeval as part of the event data for that particular event. Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html