30.11.2017, 18:49, "Jason H" <jh...@gmx.com>: >> Sent: Wednesday, November 29, 2017 at 11:05 AM >> From: "Thiago Macieira" <thiago.macie...@intel.com> >> To: interest@qt-project.org >> Subject: Re: [Interest] Packet arrival-time resolution? QUdpSocket >> >> On Wednesday, 29 November 2017 01:34:05 PST Konrad Rosenbaum wrote: >> > Any software working on a scale below 10ms needs to be realtime. Qt is not >> > realtime. Sorry. >> >> That's why the API I'm creating will give you a QDateTime, which only has >> millisecond resolution. >> >> I thought briefly about using QDeadlineTimer (which has nanosecond), but >> gave >> up since it wasn't necessary and I couldn't get the monotonic timer on most >> OSes. > > Consolidated reply, > The speed of light is ~1ft per ns, and your clock is running at ~0.33-1 ns. > There's plenty of factors to prevent absolute best performance, not even > including that the speed of light in a wire is about 1ft per 3ns, due to > inductance (multi-layer PCBs also slow it down). Meanwhile the speed of sound > is ~1.1ft per ms at STP. If I can get reliable 1 ms packet resolution and > accuracy I'll be fine. I can alter the data and node configuration to support > some jitter. As long as the hosts accurately record the event on local clock > time, and I know the offsets of each clock, can calculate the true event > time. If they are all sub ms deviation, then I can take it as-is and know > I'll be within 13 inches. > > I don't think you can say that Qt is not real-time. That's more of a kernel > issue than a software library issue.
Actually, Qt is ported to real-time operating systems, such as QNX and Integrity > > So definitely I need to use P2P for usec sync of the clocks. > > But I think as networks and CPU clocks get faster, that 1 ms will seem like > an eternity. I seem to be working just at that ms/usec boundary... > > Thanks for all your help! > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest -- Regards, Konstantin _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
