DSDPlus DSDPLUS P25 decoding audio problem

[Larry27]

I am running an SDRPlay RSP2 with SDRuno software.
I am trying to decode the local PD P25 system.
I am using Virtual Audio Cable to connect between SDRuno and DSDplus.

When the voice channel is active, the DSDplus window scroll shows that it is syncing, but the audio is
constantly breaking up. It sounds like it is coming through an audio cable with a bad connection.

Any help will be appreciated.

 

[DRL-XM43]

try reinstalling vbcable it can help

 

[mtindor]

Make sure that you have a filter width set somewhere from 9.5 khz (non-simulcast P25) up to 12.5 khz (simulcast P25) wide. Make sure you have de-emphasis turned off.

Reference this thread: https://forums.radioreference.com/threads/sdrplay-dsdplus-question.342634/

 

[slicerwizard]

Probably P25 with PSK modulation. If so, not going to work very well with a virtual cable.

 

[Larry27]

Thank you everyone for your helpful replies.
My de-emphasis was set to off, but my filter width was set to 15kHz.
I will try everything suggested here and report back ASAP.

 

[bharvey2]

I use an older version of DSD Plus with two SDR dongles to scan and decode a P25 system. I use both the -f1 and -mp switches. The first specifies the P25 protocol and the second is to optimize for PSK modulation. I'm quite happy with the results.

 

[Larry27]

Well, I have tried everything, but still no usable audio.

This appears to be a non-PSK system, because I get no audio at all when set to PSK.

I can get talkgroup info and RID, but the audio is still no good.
The scroll show good sync in both P25 and DMR systems.

Thanks again for your help.

 

[bharvey2]

Any possibility that it's multipath distortion? I'm not familiar with the SDR play but can you reduce the RF gain or attenuate it some way?

 

[Larry27]

I suppose it is possible, but I can connect my GRE 500 up to the same antenna and get a strong signal with perfect audio.

I suspect I don't have enough computer power. I am running AMD A6-5200 Quad Core at 2GHz with 6GB memory.

 

[bharvey2]

It's been a while since I've worked with an AMD based computer but it seems like you have enough horsepower to operate. I have a pretty skimpy laptop with similar specs to yours (albeit an Intel CPU) and I can run my two dongles with Untrunker and DSD+ to decode a P25 network.
Take a look at your CPU and memory stats while you're trying to decode and see if you're "pegging the meter" while running. If not, it could still be a multipath distortion issue. My SDR dongle are more sensitive to it than my Pro 668 scanner.

 

[cg]

I had a laptop with similar specs and couldn't get what I thought was decent decoding. I got rid of that and bought a used one with an Intel chil. Instantly better decoding but not as good as I wanted. I went into the power settings and set everything for better performance (shorter battery life). I then had better decoding. I did find a reference to disabling Intel SpeedStep in the BIOS and that made a difference as well. The last thing I did was to get a mobile power cable so it has full power available all the time. If I don't use that, performance suffers a bit.

Old one was a Toshiba quad core Satellite C55D-B, 4 GB ram with AMD chip
New one is Loveno T420 with an Intel Core i7-2620M

chris

 

[Larry27]

Thanks for your post Chris.
I checked the benchmarks, and your processor is at least 1.5 times faster than mine.
I had hoped to use DSDplus to decode DMR, but it is cheaper to get a new scanner than a new computer.

 

[slicerwizard]

What do Windows Task Manager and Resource Manager say? There's no need to guess at this.

 

[bharvey2]

What do Windows Task Manager and Resource Manager say? There's no need to guess at this.

I mentioned that above (didn't state Task Manager by name though) and was hoping to hear back. I think that would answer the computing power question.

 

[Larry27]

I finally got a chance to get back on the computer and experiment.
I captured the CPU usage at the same time I was getting the audio from DSDplus.


The only programs running at the time were SDRUno, DSDplus, VBcable and Snipping tool.

It looks like I don't have enough computer.

 

[simpilo]

Not sure if the RSP2 is compatible with FMP24 but you can get a P25 frequency list to make a FMP24.scanlist at

Digital Frequency Quick Import
(follow its instructions verbatim)
You can use FMP24 and DSD+ to decode P25. SDRuno is cpu intensive by itself.

P25 decodes best using FMP24 & DSD+ because we want to use its TCP loopback instead of virtual cable software. Less latency and more accurate decodes. Less I/O operations (resources). I am on a older machine 1.73ghz Intel Pentium M single core cpu with 2gb DDR2 memory 533 front side bus decoding fine runing Windows 7 Home Premium. I do have alot of features in Windows turned off too.

 

[slicerwizard]

I finally got a chance to get back on the computer and experiment.
I captured the CPU usage at the same time I was getting the audio from DSDplus.

The only programs running at the time were SDRUno, DSDplus, VBcable and Snipping tool.

It looks like I don't have enough computer.

Now click on Details and sort by CPU usage. Miss Piggy will float to the top.

I suspect that the big winner will be SDRUno. What can you do to trim its appetite? Can you reduce the I/Q sampling rate? Smaller FFT size for the spectrum display? Anything else? What do the SDRUno folks have to say about reducing feeding time at the trough?

 

[simpilo]

lol at Miss Piggy. True though.

 

[slicerwizard]

Just played with SDRUno a bit. Reducing the raw I/Q sampling rate and closing all FFT/spectrum displays significantly reduced CPU load.