On 06/10/2013 09:43 AM, Sean Nowlan wrote: > Do late packets always get dropped by the USRP? What happens if its buffers > get filled up with samples, all of which are late?
The stream args have a policy parameter. Also, these args can be set from a parameter in the USRP GRC blocks, as well as the constructor for the gr-uhd blocks themselves. This should be helpful: http://files.ettus.com/uhd_docs/doxygen/html/structuhd_1_1stream__args__t.html#a4463f2eec2cc7ee70f84baacbb26e1ef -josh > > "Marcus D. Leech" <[email protected]> wrote: > >>> L = late packet, there was a time on the packet which was> time on >>> device when >>> >>> >> There are two different "cases" for late packets happening. >> >> The first is that you haven't sent your packet far enough in advance to >> account for latency variations on the host. Unfortunately, on a >> general-purpose >> OS like Windows or Linux, latency variability can be extreme, and for >> long-running flow-graphs you might need to develop a good model to determine >> what the worst-case is and account for that. >> >> The second is that the clock on the USRP and the clock on the host will >> tend to drift apart over time, particularly if both of them are "free >> running". >> So when you schedule timed bursts far enough in advance during the >> start of a "session", it's entirely possible that after quite some time, the >> two clocks have drifted apart unfavourably in terms of allowing you >> to schedule things far enough in advance, relative to the USRP clock. >> PC clocks are *terrible* by themselves. They'll drift significant >> fractions of a second on a daily basis without any outside steering. >> The USRP >> clock, even free-running, is typically much, much better. >> >> >> -- >> Marcus Leech >> Principal Investigator >> Shirleys Bay Radio Astronomy Consortium >> http://www.sbrac.org >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
