I'm concerned that the problem Frederik is observing has to do with the very short burst he is sending, something like 5 samples. I suspect this requires 1 call each to work and tag_work per 5 sample burst, which seems like an awful lot of context switching and overhead.
-----Original Message----- From: Marcus Müller [mailto:mar...@hostalia.de] Sent: Tuesday, October 21, 2014 1:24 PM To: Nowlan, Sean; discuss-gnuradio@gnu.org; Martin Braun Subject: Re: [Discuss-gnuradio] Transmitting bursts with GRC by inserting SOB and EOB -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Sean, aaah good catch! Yes, that's right; sob is safe. Cheers, Marcus On 21.10.2014 19:19, Nowlan, Sean wrote: > From Marcus: >> ... and that (wut) might be a bug, because it implies that, if the >> stream has both a time tag and a sob tag, the question whether the tx >> metadata has a time tag depends on in which order these tags are >> sorted on the the tag storage multimap. Which might be random, >> because tags are sorted only by tag offset. >> @Martin: is there a reason that this is explicitely set to false >> here, or can one just fix this by deleting a line? > > This appears to be handled correctly. Given the same tag offset, the > order of tx_time vs. tx_sob tags should not matter. If tx_time is > found first, it sets found_time_tag=true and > _metadata.has_time_spec=true (lines 652 & 653). Then > _metadata.has_time_spec is overwritten in the tx_sob check (line > 665) with 'false', but is set back to 'true' in line 743 due to > found_time_tag being true. > > if (found_time_tag) { _metadata.has_time_spec = true; } > > If instead tx_sob is found first and tx_time second, then the time > spec will also be set in line 743. So the question is whether setting > _metadata.has_time_spec=false is really necessary. I'd say it's worth > keeping in case the user doesn't always want to use tx_time stamps. > The user may want to schedule some bursts but force others to transmit > as soon as possible while still using the ATR functionality of the > USRP. > > I know all this logic can be hard to follow, but it has to handle so > many different cases and possibly span many calls to work and > tag_work. > > From Frederik: >> Unfortunately, even with the newest version the USRP is still >> transmitting its carrier over the air. I tried both with the Message >> Burst Source as well as with the Stream to Tagged Stream Block >> combined with setting a Length Tag name in the USRP Sink. >> With the Tag Debug Block I see tx_sob+tx_eob and the Length Tag, >> respectively. They all seem to be at the right place and have the >> right value. >> >> The Length Tag should arrive properly at the Sink. I checked by >> changing the tag's name at the Stream to Tagged Stream Block to >> something stupid and finally got an "tG" printed out. > > It should be mentioned that there are two burst tag interfaces that > cannot be mixed. if a Length Tag Name is specified to the constructor, > all tx_sob and tx_eob tags will be ignored in tag_work to ensure the > interfaces are mutually exclusive. If no Length Tag Name is specified, > then tag_work will search for tx_sob/tx_eob tags and won't look for > length tags. > > Sean > > On 21.10.2014 15:53, Frederik Wing wrote: >> Hi Marcus, >>>>> I cannot believe that there is no solution to it since the >>>>> "tags_demo" application shows that it is indeed possible. >>>>> :-/ >>> that makes the two of us! I didn't get that when using tags_demo, >>> you're not seeing the carrier that you use tags_demo; as far as I >>> understood, your application does exactly the same, sending bursts >>> with sob/eob tags? >> >> That's right. tags_demo works perfectly. No carrier in between the >> bursts. The flow graph I posted before sends exactly one burst with >> SOB and EOB tags. The only difference to tags_demo I could recognize >> so far is that I don't assign time stamps to the samples. But this >> shouldn't be a problem, should it? >> >> Frederik >> >> >> _______________________________________________ Discuss-gnuradio >> mailing list Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 > > iQEcBAEBAgAGBQJURnbzAAoJEAFxB7BbsDrL2nEIAJnutUguHZy3qb0delF4EEoZ > Wh+ikhML4LpzX76omgESTBzCIL+yeSzpwyF4+xFMs/laONrFoSYjKrIPicOUC85K > pKbddIT1eYC4ulDLViEAK7G+f3h8d6fj8NvVlBOYflyz/z8kfT5Ow2P7vT2osPbi > MrY9to3MQVGHriakq6mzf5cUe/F54YmscikEofrZXZj2EqwknULehS0Q0tm/Ms0L > G+OamkGyPdsyxn8vmR2yMOScHSKxWF0yINYzf+jLJ4ypmbYUmn+99lsDZoyF9bJ3 > L93I6IaRgUReawdYjvfSmDMOL1n0t1zyp9GBgBTly4JtfD2Rcvfn8al6FSzOZv8= > =V3EN -----END PGP SIGNATURE----- > > _______________________________________________ Discuss-gnuradio > mailing list Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJURparAAoJEAFxB7BbsDrLiT8H/0qUJ6qkMEgWdp7q1eKTr3Bm hq4P6pIAXxXkmIRWVy+pn2uZ2zunvv0/2e/NcE4RMppuxTlT8HvjeKb0aKDMIxE2 spVqN/nuue5JSRAbQJIvI69jJytGgqzxvjY2EyWHSZPKtXB3Hc5a/PoMGY3EZb45 hZ+mYN0z6JpUhRlozinTkkRI3D/P38dubx5YXTSbzCthEt2BMMInS+FEpiH42KrI rKP7ywwqL0O6TFvFMlOqn9hNzJKP+PFvoJQbuH3zJSItIeRbyIth6QwERNh8Pg0H 3U19h6Y7ejnh+G8UOSOdxnlsoLHzwloYEvUb1cvBbhKeyDd4Dng8DwPa+Q6T0qo= =vsQm -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
