Hi Sakari, On Friday 21 February 2014 15:04:48 Sakari Ailus wrote: > Hi Laurent, > > On Fri, Feb 21, 2014 at 12:58:58PM +0100, Laurent Pinchart wrote: > ... > > > > It's possible to calculate it (decrementing the readout time + exposure > > > time from the end of frame timestamp) and that's what the devices > > > supposedly do. The pre-frame exposure time isn't available to the host, > > > so the end of frame timestamp cannot be calculated by the host from the > > > camera generated timestamp. > > > > > > However the link to the host is USB which has a lot more latency than > > > almost anything else which makes even hardware generated timestamps a > > > little imprecise. > > > > Why so ? There will be a jitter in frame arrival, but the hardware > > timestamp should be accurate (at least if properly generated by the > > camera firmware). > > Yes, the hardware timestamp should be accurate on its own, but as there's > delay and jitter converting that into something that's relevant on the host > adds some uncertainty. AFAIR the accuracy of the camera generated timestamp > was still much better than that of the driver generated one, right? Yes it is, as the conversion mechanism is stats-based and takes jitter and delays into account. -- Regards, Laurent Pinchart -- 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
