Missing Audio at Time

[Gregory Kaderli]

At random times the audio will not be present on SDRTrunk.

When it is working the audio quality and digital decode is the best I have experienced compared to other digital decode software.  No "digitalizing"- always good.

The first screen shot below is indicative.  I know there was audio as I was monitoring it on a desktop scanner radio. The absence of a Talk Group “Name/Number” in the sound bar may be observed. 

The second screen shot has audio working.  It indicates "Gillespie" - the agency in the sound bar.

I realize this is an old hardware configuration and a new v. of Ubuntu and a new alpha version of SDRTrunk. 

Estimate it happens about 15% of the time.

Most times it comes through. This not only happens on short transmissions but also on longer transmissions.

Running Ubuntu 20.04.1 with Gnome 3.3.3 Windowing X11

Dell Optiplex 755

8 gigabytes memory

intel Core 2 Duo CPU E8400 / 3 gHz

250 Gb hard drive but only using half as the other half is for another O/S.

Using the process of elimination, I have utilized two other new computers running windows 10 and used both the SDRTrunk V0 .4 final and the V.0.5.0-alpha3 on both computers and still about 15% of the time the audio will not be present.

SDRTrunk V.0.5.0-alpha3

RTL2832U SDR/R820T

The RTL is warmed up....after several hours.

Monitoring a P25 Phase II trunking system, non - simulcast.   770 mHz

The frequencies range from 773.281 mHz to 774.78125 mHz.

The tower is 1 miles from my location.

Using a rubber ducky with SMA connector to the RTL-SDR

(But have also used outside antenna with 50’ Times Microwave LMS 400 cable)

(Proven system to monitor 700 mHz on a desktop radio.)

The FFT display waterfall shows traffic

The spectral display shows the software has landed on the signal.

The Status shows receiving a call

The Events show Group call, duration, time etc.

I have:

Rebooted,

Used various gain settings (Incidentally one desktop radio I had would not decode if signal overload)

Tested configuration settings - using Default Mono and Default Stereo. 

Both Poly and Heterodyne on the Channelizer Type.

Max Channels from 1 to 5. 

Tried another site on this system about 14 miles away.

It is either my settings or the RTL.  Interestingly the RTL works well with another software decoder that I tried and use. That software runs on Raspbian (Raspberry Pi).    I just want to keep SDRTrunk as it has the best decode and User interface.  

I may try another RTL Dongle if I can't figure out my settings.

Other than this, the software is incomparable.

[sdrtrunk]

Greg,

I don't know if this is causing your missed audio issue, but the PPM on your tuner needs adjustment.  In the spectral display screenshots, each of the channel labels is to the right of the actual signal.

Even though you have the auto-correct enabled for the tuner, the software can lock to the signal incorrectly at multiples of +/- 2400 hertz and issue PPM corrections that keep it locked at that bad multiple.  You can manually fix this by adjusting the PPM on the tuner to align the labels to the signal and then the softare will auto adjust the PPM to keep it locked there.

I'm going to open an issue to dig into this a bit more to see if there's anything code wise that may be contributing to the missed audio.

Denny

[sdrtrunk]

Greg, one additional thought.  Next time this happens where the channel is showing in the Now Playing window but the audio is not showing in the sound bar, click on the channel in the Now Playing window and then click on the Messages tab below and grab a screen shot.  This will let me see if the traffic channel is decoding correctly and/or if there are IMBE audio frames being decoded correctly.

On Sunday, September 20, 2020 at 1:41:14 PM UTC-4 Gregory Kaderli wrote:

[Gregory Kaderli]

Thank you for the suggestions.  Regarding the spectral display screenshots and the channel label being off, this has been observed in the past. 

The display where the label is off center - only occurs when the Display>FFT Width> setting is at 512 and the Zoom is at 1x.  I set the FFT Width to 512 thinking that it would use less resources.

If the FFT Width is set to any higher number, the channel labeling appears dead on.  Would this affect the software tracking?

I do set the FFT Width to 2048 and the display label is centered but no change in audio dropping.

 

I did tinker with the PPM rate attempting to raise and lower but with no success of helping with the dropped audio.

 I was able to borrow another RTL-SDR 2838 today and experienced the same issues so it apparently is not the dongle that I am using.

Attached as requested are some screen shots labelled with working and non-working audio.

 

Perhaps you should not work on the issue presented here any longer.  I noted several transmissions today that were repeated and the users were stating traffic was not heard or did not go through.  It is interesting that I can copy some of the transmissions that the users cannot and then I cannot copy some that are acknowledged by the users.  There may be a system issue.  I will continue to monitor this site.  I will again monitor the site about 14 miles from me that is used by another agency and see if I continue to experience the same thing.  Thank you for your help.  It is great software.

[Gregory Kaderli]

Has anyone experienced this matter of missed audio on the LCRA system in Southwest / Central Texas?  It continues to plague me.  In my original post I discuss using both Ubuntu and Win10.  Different computers.  Different RTL-SDR dongles.  I acquired an Airspy Mini and experience the same issues as described in the original post.  I commented about some discrepancies in the System but those no longer appear on conventional scanner radios that I have such as the Uniden BCD536HP.  Additionally I have used another Linux based trunk decoder and it works fine.  I have used a Win10 based decoder that works with both the dongles and the RSPDx  and that software does not miss transmission audio- but the decode is less than optimal.  I  much prefer the SDRTrunk because of ease of use, the information screen and the GUI interface. The decode is great 90% of the time. It is just the missed audio.  

I also used SDRTrunk and both the RTL-SDR and the AirSpy Mini on another site on this system.  This other site is located about 15 miles from here and on 770 mHz.  I do use a proven outside antenna system.  But I experience the same missed audio.  Has anyone else experienced this?  

Greg

[Nathan Deppe]

If you monitor all of the voice channels separately, and don't monitor the control channel, do you regularly get voice to decode?

[Gregory Kaderli]

Thank you for responding.  Are you asking about receiving the audio on SDRTrunk by setting up each VOICE Channel?  I did try that just now. Recalling that I use v0.5.0 -alpha 3 which is the newer setup, I set up each voice channel in the Playlist Editor>Channels each as a separate system.  I then started "Playing" on each.  In the User Preferences>Source>Channel -Multiple Frequency I changed rotation delay to 1 second.  It does not follow well enough there to attempt to verify.  Or perhaps I misunderstood your suggestion.  Greg

[Nathan Deppe]

Correct. If you are importing from Radio Reference try selecting the voice channels, and choose Frequencies > Selected; and Configurations > For Each Frequency then Create Channel Configuration. Otherwise, enter the voice frequency as one per channel. Thus allowing you to "play" as many of them as possible, limited by your SDR bandwidth.

[Gregory Kaderli]

Yes.  I can pick up audio this way.  It is sort of a crude way....and ineffective since it doesn't track and is slow.  I am attaching a screen shot from my original post.  The program will stop on the transmission, it will indicate the event, show the information, but in the Audio Panel it won't indicate the Talk Group or Alias and there is nothing from the speaker.  I am baffled.  This happens randomly.  I have tried to pinpoint it to a particular frequency in the voice channels but it happens on all of the frequencies.  I have tried to isolate it to a talk group or site.  But to no avail.  It happens everywhere.  There is a VHF system about 40 miles away that I intend to try to monitor but the RTL-SDR and the Airspy Mini are not sensitive enough even with my outdoor antennas.  My good SDR the RSPDx regretfully won't work with SDRTrunk.  I will just keep on - keepin' on. 

[Gregory Kaderli]

I refer in the above mentioned an attachment.  Here it is. 

[wemana...@gmail.com]

On Saturday, January 2, 2021 at 1:26:30 PM UTC-5 Gregory Kaderli wrote:

I refer in the above mentioned an attachment.  Here it is. 

On Saturday, January 2, 2021 at 12:25:40 PM UTC-6 Gregory Kaderli wrote:

Yes.  I can pick up audio this way.  It is sort of a crude way....

Just to be double sure you did :

Compile and install the JMBE audio library? Either via compiling it yourself or the newer self compile built in? And then set the path to the JMBE lib in the preferences???

When you start the program you should see the lines like this:

i.g.d.a.c.mbe.JmbeAudioModule - Loading JMBE library from [/home/ /jmbe/jmbe-1.0.4.jar]  [104MB/158MB 66%]
20200608 215025.486 [sdrtrunk pool-1-thread-2] INFO  i.g.d.a.c.mbe.JmbeAudioModule - JMBE audio conversion library loaded: JMBE Audio Conversion Library v1.0.4  [105MB/158MB 66%]
20200608 215025.487 [sdrtrunk pool-1-thread-2] INFO  i.g.d.a.c.mbe.ImbeAudioModule - JMBE audio conversion library IMBE CODEC successfully loaded - P25-1 audio will be available  [105MB/158MB 66%]

[Gregory Kaderli]

Thanks for the follow up. Yes.  I am running sdrtrunk v0.5.0-alpha4 which includes the library.  And yes the path is correct.  I am assuming that was all correct as I monitor and have great reception and audio most of the time.  It is those random occasions when, the symptoms that I have previously,  described will occur. 

Interestingly I just hooked it up to my exterior antenna and set up a  totally different , different agency, different vendor, VHF system that has sites about 40 miles away.  I experienced the same issues that I have described.  I think it is all pointing to a failure in setup on my behalf.

It may be that I have attempted incorrectly to set up aliases with radio I.D.s OR I did not have enough Traffic Channels specified in the Decoder part of the channels.

I think my next plan will be to delete the entire program, the SDRTrunk directory with the info, the playlists, the java library and start over.  I realize I will have to set up my playlists again and start from scratch...but sometimes that works for me.  I will report back. 

[wemana...@gmail.com]

On Sunday, January 3, 2021 at 6:37:11 PM UTC-5 Gregory Kaderli wrote:

Thanks for the follow up. Yes.  I am running sdrtrunk v0.5.0-alpha4 which includes the library.  And yes the path is correct.  I am assuming that was all correct as I monitor and have great reception and audio most of the time.  It is those random occasions when, the symptoms that I have previously,  described will occur. 

Alpha 6 is the latest. Don't know that it will resolve issues, which are starting to appear from remote review, to possibly be setup issues most likely.

 

Interestingly I just hooked it up to my exterior antenna and set up a  totally different , different agency, different vendor, VHF system that has sites about 40 miles away.  I experienced the same issues that I have described.  I think it is all pointing to a failure in setup on my behalf.

What is the setup for antenna(s) coax? Type coax, length, splitters if any, any active splitters and/or amps? Types of antennas? separate runs of coax for each? Height of above ground, terrain? Above local scrub/terrain??

When you have a Control Selected and then in the messages tab as you see the data scroll by are you seeing any "CRC ERROR" or SYNC FAIL errors? This is indicative of signal issues or PPM issues. So double check you have the PPM setting correct for an initial lock and auto update PPM to track it.  PPM will vary slightly, even in those which have TCXO setups. It shouldn't vary as much as say the junky DVB dongles, but a slight variance is within norm/tolerances for the type of TXCO's used.

Enable logging for traffic and decoded channels on the systems.

Review the event logs in ~/SDRTrunk/event-logs

Do you see CRC ERRORS and/or SYNC FAIL which correspond to when you miss audio? This is likely RF signal level issues.

 

It may be that I have attempted incorrectly to set up aliases with radio I.D.s OR I did not have enough Traffic Channels specified in the Decoder part of the channels.

If you don't have enough traffic channels set in the tuner setup for a channel you will see  the same message as if you don't have enough RF bandwidth of the SDR's to tune to it. "No Tuner Available...." Which will cut out audio too.

For testing setup things to 16 channels, then lower as needed.

 

I think my next plan will be to delete the entire program, the SDRTrunk directory with the info, the playlists, the java library and start over.  I realize I will have to set up my playlists again and start from scratch...but sometimes that works for me.  I will report back. 

If you are a Linux user, simply keeping each version of the SDRT itself in different directory, and then if you want to start over with settings you can BACKUP your ~/SDRTrunk folder tree ie: mv ~/SDRTrunk/ ~/SDRTRunk_010421/  to keep that data if needed. SDRT will then recreate that folder upon startup to start fresh.

If you are non Linux, welp. Similar approach, but I think there are things stored in places which also need purged, and can't help there. Don't use it.

[Gregory Kaderli]

I sincerely appreciate the comments

 

“Alpha 6 is the latest. Don't know that it will resolve issues,…”

 

Thank you and I will try it.

 

“What is the setup for antenna(s) coax?.......logs etc….Errors…”

 

Some of that is covered in my original post.  While I don’t want to ignore those possible issues, and without going into great detail…I have a high degree of certainty that it is not signal issue.  I am aware of this and have paid attention to the Messages.  That does not appear to be an issue.

 

“If you don't have enough traffic channels……For testing setup things to 16 channels,”

 

1.       Does the number of channels need to take into account the data calls, the registrations, the responses, etc.?

2.       Doesn’t it present a problem with the computer processor if I set the number of channels too high?

 

“If you are a Linux user, simply keeping each version of the SDRT itself in different directory,…….”

 

Wonderful point for which I thank you.

Regarding this comment, are there dependencies in other areas that need to be removed if I delete older

“sdr-trunk….” Directories?  Will “sudo apt-get autoremove” take care of other areas if I delete the sdr-trunk directory first?

[wemana...@gmail.com]

On Monday, January 4, 2021 at 3:08:48 PM UTC-5 Gregory Kaderli wrote:

Some of that is covered in my original post.  While I don’t want to ignore those possible issues, and without going into great detail…I have a high degree of certainty that it is not signal issue.  I am aware of this and have paid attention to the Messages.  That does not appear to be an issue.

 

50ft LMR 400 is good. 1M from tower? Then you should have no issues.

But? What type of antenna is at the other end? 800MHz tuned, discone (pfft, junk not a fan), other?

 Duck antennas again, type? I use numerous actual LMR antennas designed for various things with 3-5db gain, and some that are 0db gain.

Things that can affect a signal if you inside are building construction. For my main 850Mhz system who I can see, literally see, the tower, being inside my Faraday cage house not an issue. 2 other systems within about 4-6 miles each, not happening unless I am near a window.  Same for even another 850Mhz thats about 9 miles away.

So concrete block and brick are not great for RF to penetrate. Some homes will have film or coatings on the windows that absorb RF. Some roofs are bad ie: metal roof. Some roofs even shingle or tile have a backer that is coated in metal, again bad. These all can attenuate signals to the point they cause issues.

The big thing to consider here is: Too much gain!

What do you have the gain settings at on the tuner tab? If you've got it to 49.6 turn it down. Something like 20-32 is more than adequate. if you are 1 m from the tower.

The VHF system at 14 miles will likely need max gain, even on the outside antenna.

Does the loss of audio occur on a specific frequency(s) each time or multiple?

Why well. the antenna for some channels may be lower on the tower v. others. Or even the base could be lower powered for that channel. I have one system which is limping along till the P25 conversion. And some channels are much stronger than others due to the bases which have been worn out from being the control channel. The amps have reduced power on them. Some by quite a bit, its noticable even to users. It only has to hold on for a little while longer with the spit and tape. Parts are not available for some of the issues, and there is zero reason to fix the bases since they will be decommissioned soon.

 

1.       Does the number of channels need to take into account the data calls, the registrations, the responses, etc.?

2.       Doesn’t it present a problem with the computer processor if I set the number of channels too high?

The # of channels for the tuner is for DATA CALLs and TRAFFIC aka VOICE which in P25 are really the same thing in essence its just data of voice present. But for clarity, if your system has 8 actives calls and 9 are voice and 1 data, you will miss 1 call regardless of type. Set the ignore data setting in the system. There is really not much you can do with with, mostly, mostly. Nearly all of its encrypted for the good stuff, and I not aware of SDRT doing any thing to deal with the short burst data of enroute, on scene, clear etc. from the various buttons in most FD/EMS and some LE. Although FirstNet (pfft bleck!) is starting to suck up alot of this data traffic in areas.

 

Processing power plays a part of this in # of channels.

I use a junky dual core centrino or something to lug around till recently, I've put OH MARCS and MI MSPS on it full bore flood of audio, with no issues of missing audio except due to the flood. Thats way less power than what you are listing.

Registrations/affiliations etc. are control channel data, which occur on that CC. That has nothing to do with traffic channels.

Wonderful point for which I thank you.

Regarding this comment, are there dependencies in other areas that need to be removed if I delete older

“sdr-trunk….” Directories?  Will “sudo apt-get autoremove” take care of other areas if I delete the sdr-trunk directory first?

SDRT is not installed via APT on Linux. Its just an archive of the program and all dependencies for it are in the zip file you download, including Java.

So you do NOT need apt-get for anything in this.

This is what I do

mkdir 050a6

cd 050a6

cp ~/Downloads/sdrtrunk.......zip .

unzip sdrtrunk....zip

cd sdrtrunk[version]/bin

./sdr-trunk

When a new version comes out I rinse repeat.

so the only real change is mkdir 050a7 or what ever if its a newer point it would be 060a1 etc..  This way I can go back to an earlier version if needed due to problems, or comparison needs for bugs etc..

You can back up the data used by doing

mv ~/SDRTrunk ~/SDRTrunkData010521 or a true back up cp -r ~/SDRTrunk ~/SDTrunk_010521 etc..

Then SDRT will create a new folder when it starts.

You could use some unzip options to force it to not create another level of dir tree, I am just too lazy to do it when I run it. It doesn't matter really.

[Jim Kovalsky]

I'm seeing some missing audio, but it seems to always be on a single talk group.  It's the automated dispatch voice -- if I listen on the scanner I hear it all.  About 10-15% of them are cutting out through SDRTrunk Alpha 6.  I do notice that talk group is substantially louder than all of the others, so it may be related.

[wemana...@gmail.com]

On Tuesday, January 5, 2021 at 11:13:11 AM UTC-5 jkova...@gmail.com wrote:

I'm seeing some missing audio, but it seems to always be on a single talk group.  It's the automated dispatch voice -- if I listen on the scanner I hear it all.  About 10-15% of them are cutting out through SDRTrunk Alpha 6.  I do notice that talk group is substantially louder than all of the others, so it may be related.

ONE TG with issues, points to a likely issue with patch{s} and/or multiselects, they are different things.

Is ONE TG? Ie: the Locution TG and it is patched to a VHF/UHF channel for alerts/paging/"minitors?"

An issue where ANY TG on THE SAME FREQUENCY(S) is an issue RF wise which is likely related to signal conditions from the source being impacted at your RX location from terrain, ie: hills, buildings, scrub ie: trees etc..

Are you monitoring multiple CC's where the same TG(s) with issues may be present? Which could cause an issue with the deduplication code.

[Gregory Kaderli]

wemanage wrote, "50ft LMR 400 is good. 1M from tower? Then you should have no issues."

Great information and I thank you.  I believe I have it solved!  Running 72 hours now and nothing missed.  Regretfully I cannot spend much time monitoring now and the local agency uses in car computers to transfer info so not alot of voice traffic but I think I figured it out.

I will comment in the coming week so as to share but I want to see if I can recreate the problem.  As of now it is pointing to user error. Thanks for the reminder on how to save all the versions and test each one.