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OP25 audio and errors

MCWKen

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Mar 4, 2013
Messages
17
Location
Mason City
Good evening. Having finally gotten OP25 to work, have been tweaking some of the known changes to improve audio and stability. However, it is still has a bass sound to it, and sometimes choppy at the beginning or end of transmissions.



I suppose this should have been prefaced by the fact that I am a neophyte when it comes to Linux, and without the help and observations on this board, would have never gotten OP25 to run.



I did see over and over again, someone suggesting that boatbod run instead of osmocom. There were some instructions how to get it, but I am not sure where to install it. Again, pardon me for being so green.



Lastly, and odd occurance last night. The tower here handles two counties, and the State Patrol. While listening, one county had a call from Radio Service about their issue at their local tower, and so forth. The volume of Radio Service was much louder than other users on this tower. After that conversation ended, the other county talk groups showed transmitting in the Terminal, yet there was no audio. Same went for the State Patrol talk group. But the original County talk group still came in, and sounded as usual. The only way to fix this was to quit OP25 and restart it.



Is this something I did not configure correctly?



Thanks in advance.



Below is how I run OP25, and the stderr.2 file.



Command line:

./rx.py --args 'rtl' --gains 'lna:39' -S 1000000 -f 770.406250e6 -o 15550 -x 02 -q 52 -T trunk.tsv -2 -U 2> stderr.2



STDERR file:



gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.11

built-in source types: file osmosdr fcd rtl rtl_tcp uhd plutosdr miri hackrf bladerf rfspace airspy airspyhf soapy redpitaya freesrp

Using device #0 Realtek RTL2838UHIDIR SN: 00000001

Found Rafael Micro R820T tuner

[R82XX] PLL not locked!

Exact sample rate is: 1000000.026491 Hz

[R82XX] PLL not locked!

[R82XX] PLL not locked!

Using two-stage decimator for speed=1000000, decim=10/4 if1=100000 if2=25000

Project 25 IMBE Encoder/Decoder Fixed-Point implementation

Developed by Pavel Yazev E-mail: pyazev@gmail.com

Version 1.0 (c) Copyright 2009

This program comes with ABSOLUTELY NO WARRANTY.

This is free software, and you are welcome to redistribute it

under certain conditions; see the file ``LICENSE'' for details.

op25_audio::eek:pen_socket(): enabled udp host(127.0.0.1), wireshark(23456), audio(23456)

p25_frame_assembler_impl: do_imbe[1], do_output[0], do_audio_output[1], do_phase2_tdma[1], do_nocrypt[0]

metadata update not enabled

audio device: default

Allocating 15 zero-copy buffers

1561862163.880817 PCM underrun

1561862375.011933 PCM underrun

1561862406.744887 PCM underrun

1561862411.071818 PCM underrun

1561862669.531946 PCM underrun

1561862708.089488 PCM underrun

1561862712.942487 PCM underrun
 

boatbod

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Talbot Co, MD
There are differences in features and functionality between Max's version of op25 and mine. Best I can say is try them both and see which works best for you.

Audio buffering is a big item when it comes to audio stutter, especially on a virtual machine rather than a native os. Previous wisdom was to eliminate Pulse Audio and use ALSA directly, but these days I think you're better off using Pulse Audio with liquidsoap as the glue between op25 and the sound drivers.
 

MCWKen

Member
Joined
Mar 4, 2013
Messages
17
Location
Mason City
Well now it has gotten worse once I installed boatbod's op25.

OP25 works okay when it first starts, but when a second frequency is received, it freezes up.

1562643788121.png

Next, here is the control line:

1562643909585.png
Finally, the stderr.2 file:

1562644009318.png

Not sure where to go from here.

Any suggestions?
 

boatbod

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I believe the last few lines of the stderr.2 log amply explain what the problem is.

You need to adjust your ppm error correction, and considering you are not using a tcxo dongle, be ready for the frequency to drift again after you have had the app running for a few minutes.
 

MCWKen

Member
Joined
Mar 4, 2013
Messages
17
Location
Mason City
After reading your post, I opened GQRX and ran it for about 20 hours. Mind you I was not in front of the computer all the time, however from start to finish, it stayed right on 770.406250 without deviation with an adjustment of 52 ppm which I had used before.

I then decided to re-install OP25 and all it's associated packages. Since 0300, it has run flawlessly. GQRX still shows the dongle right on frequency.
 

MCWKen

Member
Joined
Mar 4, 2013
Messages
17
Location
Mason City
Just curious, what is that software on the left of your screen shot?
That is Win500. Since the Iowa P25 State Radio is new, many municipalities and counties have joined the system. Using Win500 allows me to log talkgroup usage. Since the Whistler cannot translate Phase II TDMA, it can at least help me out in identifying new services (one has to change it from P25 auto to P25 manual).

I later translate that information into OP25's tsv.
 

DRL-XM43

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Messages
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Location
Durham Region
After reading your post, I opened GQRX and ran it for about 20 hours. Mind you I was not in front of the computer all the time, however from start to finish, it stayed right on 770.406250 without deviation with an adjustment of 52 ppm which I had used before.

I then decided to re-install OP25 and all it's associated packages. Since 0300, it has run flawlessly. GQRX still shows the dongle right on frequency.
Bear in mind an error of 1 ppm can prevent the decode, as I found out through experience, a dongle which is -q 52 could present a challenge.

see this thread https://forums.radioreference.com/threads/op25-tuning-question.388480/
 
Last edited:

MCWKen

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Mar 4, 2013
Messages
17
Location
Mason City
I will be replacing the generic RTL with a NooElec NESDR Smart Premium RTL-SDR as soon as I get an antenna put out for it. Hanging out a window 7 stories up is not my cup of tea, so will have to wait for someone to install it for me.
 

DRL-XM43

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Jun 23, 2015
Messages
335
Location
Durham Region
I will be replacing the generic RTL with a NooElec NESDR Smart Premium RTL-SDR as soon as I get an antenna put out for it. Hanging out a window 7 stories up is not my cup of tea, so will have to wait for someone to install it for me.
I can add that NooElec NESDR Smart Premium RTL-SDR works extremely well for me so I replaced all my high ppm dongles with them, 6 to date.
 

boatbod

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Mar 3, 2007
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Location
Talbot Co, MD
I can add that NooElec NESDR Smart Premium RTL-SDR works extremely well for me so I replaced all my high ppm dongles with them, 6 to date.
The old dongles are ok but you have to keep them running so they stabilize, then adjust ppm while hot. After that they run great until you turn them off and let then cool down.
 
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