One thing I need to clarify - when I say type 2 is a 3600 baud 2FSK system, I am
referring to the control channel only. The voice channels are, of course, C4FM.
The really strange thing is that I have been over the DSD source code, and it decodes
voice by specifically looking for LDU1 and LDU2 frames. If OP25 is detecting HDU frames,
then DSD should be also..
Cheers,
Matt
--- In op25-dev(a)yahoogroups.com, "rrgsti" <bobrich@> wrote:
Interesting! I did see on the MARCS page at
Ohio.gov say that they were planning to
upgrade to P25, which was a bit confusing.
These are the control channels I'm able to see in UniTrunker with my little home-brew
antenna. These are all around central/western ohio. The first one is the only analog
system, and the signal is pretty poor.
http://i.imgur.com/CoNGl.png
I am able to decode the voice channels a bit in DSD on Windows as well. It's
somewhat odd, as the voice, when it's smoothly decoded, is very high quality, but it
drops out quite a bit. I'm doing it through the audio output of HDSDR, though, which
is probably where the issue is.
Anyway, DSD does kick out some diagnostic info as well if that's of any use. I can
also get snapshots from Wireshark of the P25 CAI.
I do appreciate any effort put into this but please enjoy your weekend first and
foremost. :)
Take care.
--- In op25-dev(a)yahoogroups.com, "Matt" <matt.robert80@> wrote:
>
> Aha - the plot thickens. Ohio MARCS isn't a true P25 system - its an old Type 2,
3600 baud 2FSK Motorola trunk system that has Motorola ASTRO CAI compatible voice
channels.
>
> These systems were implemented between 1996 and 2002 which is after Motorola ditched
VSELP as their codec and went to the CAI IMBE format that was ratified in 2002 as the real
P25 standard. These systems supported analog voice also, however MARCS has dropped that
and is only using digital voice.
>
> These ASTRO voice channels use the same IMBE vocoder as a true P25 system, and a
very similar CAI compatible format, but the usual P25 fields are used for other purposes.
The NSWGRN used to use this before it went pure P25.
>
> OP25 has been implemented to the P25 specs, which differ slightly form these
systems.
>
> The NAC values are calculated on these systems by a combination of the Type 2 System
ID, and the Analog connect tone code. Anyone who played with the old classic trunker on
3600 baud systems will recall this.
>
> If you could list which site you are listening to and the system ID, I can look into
it further from some old notes that I have lying around.
>
> --- In op25-dev(a)yahoogroups.com, "rrgsti" <bobrich@> wrote:
> >
> > The capture is from a local repeater in the Ohio MARCS system. I get pretty
strong signals from a few of them, I believe this one in particular was from London, Ohio
in Madison county (the control channel may actually be in there as well). I do know that
RadioReference streams this repeater through a Uniden BC796D digital scanner.
> >
> > I'd be happy to capture more if it's of any use or upload the files to
another location.
> >
> > Thanks
> >
> >
> > --- In op25-dev(a)yahoogroups.com, Matt Robert <matt.robert80@> wrote:
> > >
> > > I thought the same thing but then recalled that 000 is not available as a
NAC - the standard defines the value as having the range 0x001-0xFFF.
> > >
> > > I think a capture file would be ideal - this is a curly one for sure!
> > >
> > > Bob - which system is this coming off?
> > >
> > > Cheers,
> > > Matt
> > >
> > >
> > > ________________________________
> > > From: Steve Glass <stevie.glass@>
> > > To: op25-dev(a)yahoogroups.com
> > > Sent: Thursday, 3 May 2012 11:31 AM
> > > Subject: Re: [op25-dev] Re: OP25 GRC - Almost but not quite working
> > >
> > >
> > > Â
> > > The 64 bit NID consists of the NAC+DUID (the low order 16 bits) and the
error correction bits (the high order 48 bits). Its possible the NAC is zero for a data
frame since it has its own addressing information within the frame itself. That would
leave you with just the DUID and the appropriate BCH code for that value. Its possible
(but not very likely) that this would mean the high order bits would be mostly zeroes.
> > >
> > >
> > > On 3 May 2012 01:02, rrgsti <bobrich@> wrote:
> > >
> > >
> > > >Â
> > > >Hi folks,
> > > >
> > > >I'm still tinkering with this but am running into a bit of a wall
with regards to P25 data.
> > > >
> > > >These two lines are dumped to stderr using a call to the dump_cw
function that I added to the code. I'm only dumping the first 30 bytes for brevity:
> > > >
> > > >
> > > >55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff ff
ff ff ff fe fc 25 ed
> > > >
> > > >55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 5b 10 ba 16 de 2e 82 69 36
3d 98 1f 9b f8 8e c6
> > > >
> > > >
> > > Based on what I've been able to determine so far, the first 48 bits
are frame sync, and they should be fixed at 0x5575f5ff77ff, which is what we see above.
> > > >
> > > >The next 64 bits are supposed to be NID, which includes the DUID.
> > > >
> > > >I could be wrong, but I believe the 02 (which alternates between 02
and 03 in the lines below) at the 9th byte, is the status bit-pair that is interleaved
every 70 bits (9 bytes * 8 bits - 72 bits into the frame). Once removed, that shifts the
remaining bits to the left 2, which still leaves the NID essentially filled with zeroes
except for the last two bits. Immediately after the NID, however, the bits start flying
again.
> > > >
> > > >Does this seem normal? I can't really find any annotated hex
dumps of a P25 frame to try to line things up, but it seems that the NID should be
populated with something other than zeroes. If you bit shift the 15th bit 2 to the left,
we'll get a parity bit set every now and then (again, unless I'm messing something
up), but nothing else.
> > > >
> > > >I'm completely open to the fact that this could just be a bad
signal, but I can get very clear decodes of the voice if I force the type to LDU1 or LDU2,
and I have never seen anything but all zeroes here (across many minutes of decoded voice
data)
> > > >
> > > >Any thoughts?
> > > >
> > > >
> > > >--- In op25-dev(a)yahoogroups.com, "rrgsti" <bobrich@>
wrote:
> > > >>
> > > >>
> > > >> Hi Matt!
> > > >>
> > > >> Thanks for the info, it sounds like that is a very possible
option. Is there a way to see the state of the fsk4 demodulator? I did try running with
the updated OP25.py that Balint put out on Saturday (uses _op25.fsk4 instead of the Radio
Raush module, and it doesn't seem to behave any differently.
> > > >>
> > > >> I did find dump_cw in op25_imbe_frame.h and used it to dump
frames right before their duid is read. I don't know if these will be meaningful, but
I'll paste them in here. Moments of silence have the clusters of 0xff's on the
right, while portions where there is audio has more random numbers.
> > > >>
> > > >> I did note that about 9 bytes into this dump there is a byte that
keeps flipping between 2 and 3. Is it possible this is where the DUID is (shifted a bit or
two). Each row starting with 0x55 0x75 is a new frame dumped, I only dump the first 32
bytes or so of each one.
> > > >>
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 03 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 5b 10 ba 16 de 2e 82 69
36 3d 98 1f 9b f8 8e c6
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 74 35 56 de 42 7b ac 05
90 af 5a 0e 12 84 81 6b
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 52 0b 37 d6 c5 a6 11 79
56 f5 9b 1a 1e 22 8a 35
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 7e 2d f0 82 d0 4f f8 4d
a2 61 34 94 52 a4 f8 ec
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 4e 46 60 ce 5d a8 8b 27
7f 62 78 ab c2 52 ee 0f
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 00 00 00 02 55 75 f5 ff
77 ff 2d 6f ae e2 78 2e
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 03 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff ff fc 25 ed
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 45 5e a4 8b 59 7f 74 31
29 f3 ed d2 36 6c fa 30
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 46 33 55 22 52 69 8e 51
5c 01 0b ae 5a eb 36 8f
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 5b 10 ba 16 de 2e 82 69
36 3d 98 1f 9a f8 8e c6
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 00 00 00 02 55 75 f5 ff
77 ff 2d 6f ae e2 78 2e
> > > >> 55 75 f5 ff 77 ff 00 00 02 00 00 00 00 00 01 26 2d 02 0f 68 4f ff
ff ff ff ff fe fc 25 ed
> > > >>
> > > >>
> > > >>
> > > >
> > > >> --- In op25-dev(a)yahoogroups.com, Matt Robert
<matt.robert80@> wrote:
> > > >> >
> > > >> > Hi Bob,
> > > >> >
> > > >> > Its more than likely a result of a bad signal. The FSK4
demod tends to output zeros when it loses sync which is why the DUID is erroneously coming
up as 0x00.
> > > >> >
> > > >> > LDU1/2 are the two types of voice frames. LDU1 has
signalling data embedded and LDU2 has encryption sync data embedded.
> > > >> >
> > > >> > The kludge diff posted below will work - but only for valid
frames with a corrupt DUID value.
> > > >> >
> > > >> >
> > > >> > I'm sure the root cause is the FSK4 demod isn't
locking properly and causing a bad DUID value to be outputted. I have seen similar
behaviour in other areas of OP25 - for example I was looking at the IV/MI value (72 bits)
on a local P25 system here. Whenever the demodulator ran out of talent, it would output
steams of constant zeros.
> > > >> >
> > > >> > Ohio MARCS is a Type 2 Smartzone Omnilink System with CAI
compatible ASTRO voice channels - so its essentially P25 compatible. The P25 CAI spec was
based on the ASTRO CAI from the same era, so its essentially the same thing.
> > > >> >
> > > >> > Is the system running any form of simulcasting?ÃÂ
> > > >> >
> > > >> > Cheers,
> > > >> > Matt
> > > >> >
> > > >> > ________________________________
> > > >> > From: rrgsti <bobrich@>
> > > >
> > > >> > To: op25-dev(a)yahoogroups.com
> > > >> > Sent: Thursday, 26 April 2012 10:59 PM
> > > >> > Subject: [op25-dev] Re: OP25 GRC - Almost but not quite
working
> > > >> >
> > > >> >
> > > >> > ÃÂ
> > > >> > Quick update from my end.
> > > >> >
> > > >> > It looks like every frame coming out of the fsk4 demodulator
(I'm assuming, still a n00b here) is marked with a 'duid' of 0x0.
Consequently, when data_unit.cc initializes a new data_unit from the frame, it is always
creating it as an HDU (P25 header) type. This then prevents the IMBE decoder from being
executed b/c it's not a voice data unit type (LDU1/LDU2 (no idea what these mean)).
> > > >> >
> > > >> > I figured maybe it has something to do with our system (Ohio
MARCS) not being full P25 compliant and not including metadata of any sort, so I just made
the following change to data_unit.cc and re-ran it:
> > > >> >
> > > >> > --- op25-orig/blocks/src/lib/data_unit.cc 2012-04-24
10:31:29.139694592 -0400
> > > >> > +++ op25/blocks/src/lib/data_unit.cc 2012-04-26
08:12:35.183962129 -0400
> > > >> > @@ -39,7 +39,8 @@
> > > >> > uint8_t duid = extract(frame_body, 60, 64);
> > > >> > switch(duid) {
> > > >> > case 0x0:
> > > >> > - d = data_unit_sptr(new hdu(frame_body));
> > > >> > + //d = data_unit_sptr(new hdu(frame_body));
> > > >> > + d = data_unit_sptr(new ldu1(frame_body));
> > > >> > break;
> > > >> > case 0x3:
> > > >> > d = data_unit_sptr(new tdu(frame_body, false));
> > > >> >
> > > >> > This seemed to sort of work as I now get rather garbled, but
intelligible, audio from the decoder.
> > > >> >
> > > >> > I've uploaded the baseband capture (1Msps) and resulting
audio .wav file that I get at the following URLS:
> > > >> >
> > > >> >
http://s3.amazonaws.com/public-xrp/p25.iq.bz2
> > > >> >
http://s3.amazonaws.com/public-xrp/p25.wav
> > > >> >
> > > >> > Not sure if this is of any use, but it is encouraging to
hear voices at least. :)
> > > >> >
> > > >> > Thanks!
> > > >> >
> > > >> > Bob
> > > >> >
> > > >> > --- In op25-dev(a)yahoogroups.com, Andy Knitt
<andyknitt@> wrote:
> > > >> > >
> > > >> > > It looks like imbe_decoder_factory.cc in OP25 defaults
to
> > > >> > > 'software_imbe_decoder'. I manually changed
the IMBE environment variable
> > > >> > > to "soft" and confirmed it with printenv, but
I'm still getting a flat line
> > > >> > > at the output of the OP25 block. Any other ideas?
> > > >> > >
> > > >> > > Thanks,
> > > >> > >
> > > >> > > Andy
> > > >> > >
> > > >> > > On Mon, Apr 23, 2012 at 11:47 PM, Balint
<balint256@> wrote:
> > > >> > >
> > > >> > > > **
> > > >> > > >
> > > >> > > >
> > > >> > > > I *still* haven't checked out the latest code,
but in my old code the
> > > >> > > > default voice frame output was (null?).****
> > > >> > > >
> > > >> > > > There are options for file output, null, external
(hardware) decoder and
> > > >> > > > internal decoder. You used to be able to spec this
on the command line as
> > > >> > > > an environment variable:****
> > > >> > > >
> > > >> > > > export IMBE=soft****
> > > >> > > >
> > > >> > > > I changed my default to be the internal decoder
(see
> > > >> > > > `imbe_decoder_factory.cc').****
> > > >> > > >
> > > >> > > > ** **
> > > >> > > >
> > > >> > > > *From:* op25-dev(a)yahoogroups.com
[mailto:op25-dev@yahoogroups.com] *On
> > > >> > > > Behalf Of *Andy Knitt
> > > >> > > > *Sent:* Tuesday, 24 April 2012 12:45 PM
> > > >> > > > *To:* op25-dev(a)yahoogroups.com
> > > >> > > > *Subject:* [op25-dev] OP25 GRC - Almost but not
quite working****
> > > >> > > >
> > > >> > > > ** **
> > > >> > > >
> > > >> > > > ****
> > > >> > > >
> > > >> > > > I have the OP25 GRC demo that Balint provided up
and running.
> > > >> > > > Everything seems to working except I'm not
getting any audio out of
> > > >> > > > the OP25 block. I'm getting the "four
line" output from the dibit
> > > >> > > > output port when there is traffic on the channel,
and the autotune
> > > >> > > > output is outputting data. However, no audio. I
put a scope on the
> > > >> > > > audio output and it's a flat line at zero,
even when the dibit output
> > > >> > > > is "four lines". Any tips on how to
further troubleshoot?
> > > >> > > >
> > > >> > > > Thanks,
> > > >> > > >
> > > >> > > > Andy****
> > > >> > > >
> > > >> > > > ****
> > > >> > > >
> > > >> > > >
> > > >> > > >
> > > >> > >
> > > >> >
> > > >>
> > > >
> > > >
> > >
> >
>