Thanks for the report. Going to move this one offlist -- have some stuff for you to try.
--n On Tue, May 13, 2014 at 8:34 AM, Andy Walls <a...@silverblocksystems.net>wrote: > > > On Fri, 2014-04-25 at 17:22 -0400, Andy Walls wrote: > [snip] > > > On Fri, Apr 25, 2014 at 2:14 PM, Andy Walls > > > <a...@silverblocksystems.net> wrote: > > > Hi. > > > > > > What is the recommended gr-ais repo/branch/commit that yields > > > a working > > > gr-ais with GnuRadio 3.7.x (git commit > > > 3831dd37c8df19e25fa258db4d393ee068889dae) > > > and the Ettus UHD 3.7.1 > > > > > > GitHub shows this fork network: > > > https://github.com/bistromath/gr-ais/network > > > > > > Right now I'm using bistromath/gr-ais commit > > > 754c13ca4f1c3fb0d079d3a42002b0dade2268ff > > > (master HEAD, IIRC), but I'm not getting *any* !AIVDM output > > > to the terminal window. > > Well, I've identified one problem. > > The "unstuff" operation is being applied before the correlator for the > start flag of 01111110 (0x7e). The start flag, end flag, and preamble > are not subject to bit stuffing per ITU-R M.1371-4 Annex 2 Sections > 3.2.2.1 through 3.2.2.4. > > I suspect this causes a problem with proper detection of the start of > the message, as the unstuff, as I understand it, will change the start > flag from 01111110 to 0111110m, where m is the first bit of the message > payload. > > Putting the unstuff operation after the correlators doesn't fix > everything though. All potential message decodes still fail the CRC > check. > > Bypassing the CRC check and inspecting the output !AIVDMs with gpsdecode > verifies they are junk. :( > > Regards, > Andy > > >
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