On Mon September 17 2012 11:18:58 Laurent Pinchart wrote: > Hi Sylwester, > > On Sunday 16 September 2012 23:59:42 Sylwester Nawrocki wrote: > > On 09/16/2012 05:33 PM, Laurent Pinchart wrote: > > > On Sunday 16 September 2012 15:57:14 Hans Verkuil wrote: > > >> On Sat September 15 2012 22:16:24 Sylwester Nawrocki wrote: > > >>> On 09/15/2012 02:35 PM, Hans Verkuil wrote: > > > >>> Have anyone has ever come with a use case for switching timestamps clock > > >>> type, can anyone give an example of it ? How likely is we will ever need > > >>> that ? > > >> > > >> Well, ALSA allows you to switch between gettimeofday and monotonic. So in > > >> theory at least if an app selects gettimeofday for alsa, that app might > > >> also want to select gettimeofday for v4l2. > > Does it, in its kernel API ? The userspace ALSA library (or possibly > PulseAudio, I'd need to check) allows converting between clock sources, but I > don't think the kernel API supports several clock sources. Through the SNDRV_PCM_IOCTL_TTSTAMP ioctl AFAICT. Regards, Hans > > > OK, I'm not complaining any more. :) > > > > >> I'd really like to keep this door open. My experience is that if > > >> something is possible, then someone somewhere will want to use it. > > > > Indeed, caps flags approach might be too limited anyway. And a v4l2 control > > might be not good for reporting things like these. > > > > > As far as system timestamps are concerned I think the monotonic clock > > > should be enough, at least for now. Raw monotonic could possibly be > > > useful later. > > > > > > Another important use case I have in mind is to provide raw device > > > timestamps. For instance UVC devices send a device clock timestamp along > > > with video frames. That timestamp can be useful to userspace > > > applications. > > > > Could be interesting to add support for something like this. Of what format > > are then such device timestamps ? > > They're device-dependent :-) In the UVC case they're 32-bit integers. > > -- 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
