Current consensus on P25 streaming setup on Raspberry Pi?

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dextergiii

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Firstly, thank you to all the contributors on this site. I'm an extreme noob to SDR but I've been able to leverage the information here to setup my system using 2 SDR dongles, SDRtrunk, and am now streaming to broadcastify. Yesterday I was listening to the feed and heard mention of the tac teams switching to BDC V-15, etc... I wanted to tune in but then realized I'd disrupt the broadcastify feed.

Ultimately, I'm curious how to get around this constraint. I first thought about using a Raspberry Pi... there's a lot of information here about streaming AM or AirTraffic using the bcfy image (which I'm struggling to understand how to incorporate trunking capability). I've also found a lot of information using hardware scanners plugged into a Pi soundcard which doesn't apply to my setup. Lastly, using a pi might transfer the processing burden from my desktop to a raspberry, but still not allow me to play around with the same dongles while streaming.

Is it possible to use a Raspberry Pi to not only stream a P25 system but also act as a local tcp server which I could access via my desktop to tune into frequencies other than & without disrupting the stream? If not, is there an efficient way to simultaneously stream and "play around" without buying 2x antennas, receivers, laptops, etc?

Thanks in advance for anyone's input.
 

SaSal

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If the SDR's are being used for streaming - then no - cannot play around and keep the stream up.

Adding additional SDR's however would then allow you to play - no need for extra antennas or laptops though. - use a coax splitter - comes in various flavors - and hook all the SDR's up to the 1 antenna via the splitter . As for laptop - use a good quality powered USB hub, - and run the SDR's through the hub.

As for offloading - depends on what you plan here; A Pi-4 will do decoding and streaming ok - but would be very very hesitant to then get it also running as a TCP server for extra SDR's, this is also affected by just how busy the system is you are monitoring and streaming.
 

boatbod

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My feed servers are separate from the system I use for informal monitoring/listening/development. There's really no other way to do it if you want to provide a useful service to others.
 

dextergiii

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I really appreciate the feedback... sorry for the delay in responding.

Due to the constraints you mentioned (a dongle cannot be used for both streaming and playing around), I settled on a RPi4 running OP25 for now... It's still not streaming, and I can't yet hear audio :ROFLMAO:, but I can see it's tracking the P25 system via one dongle & obviously lacking the bandwidth. It's a learning curve so progress is slow. Hopefully I can get it working without taking the $300 plunge on a RSPduo.

Will the "always on" bias tee of the nooelec dongle's be a problem if using a simple splitter & shared antenna?
 

SaSal

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I really appreciate the feedback... sorry for the delay in responding.

Due to the constraints you mentioned (a dongle cannot be used for both streaming and playing around), I settled on a RPi4 running OP25 for now... It's still not streaming, and I can't yet hear audio :ROFLMAO:, but I can see it's tracking the P25 system via one dongle & obviously lacking the bandwidth. It's a learning curve so progress is slow. Hopefully I can get it working without taking the $300 plunge on a RSPduo.

Will the "always on" bias tee of the nooelec dongle's be a problem if using a simple splitter & shared antenna?
1 SDR is able to track and decode a P25 trunk with ease, not sure what you mean with lacking bandwidth.
As for sound, assuming you have speakers plunged in - do you hear anything if you do a "speaker-test -c 2" (Remove quotes) ?.
 

dextergiii

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What I meant about the bandwidth is... I was under the impression that the traffic could be captured if it fell within the spectrum... One tuner would generally stay locked on the control channel and the other would bounce around often outside the CC spectrum chasing traffic. I was also under the impression despite encrypted calls being "ignored", they are simply muted in SDRTrunk... so I am curious how much traffic is lost due to the tuner being briefly tied up on encrypted calls... I'll be able to test once I get the pi set up. But as I admitted to being a noob, I'm happy to be corrected if I'm not understanding this correctly.

To your other question, I did not hear anything using "speaker-test -c 2" but was able to hear using "speaker-test -Dhw:Headphones -c2" so I have more work to do on the configuration files.
 

SaSal

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What I meant about the bandwidth is... I was under the impression that the traffic could be captured if it fell within the spectrum... One tuner would generally stay locked on the control channel and the other would bounce around often outside the CC spectrum chasing traffic. I was also under the impression despite encrypted calls being "ignored", they are simply muted in SDRTrunk... so I am curious how much traffic is lost due to the tuner being briefly tied up on encrypted calls... I'll be able to test once I get the pi set up. But as I admitted to being a noob, I'm happy to be corrected if I'm not understanding this correctly.

To your other question, I did not hear anything using "speaker-test -c 2" but was able to hear using "speaker-test -Dhw:Headphones -c2" so I have more work to do on the configuration files.
Right, yeah understand on what you mean now, reason was questioning is I had also hit the USB bandwidth limit on a USB 2 hub with many SDR's hanging off it - things started getting screwy until splitting them over a few hubs etc.

Not sure on SDRTrunk as not used that as yet - for pi - using OP25 atm.
 

boatbod

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With op25, one dongle will happily frequency hop wherever it needs. Also, P25 signals voice grants and updates on the traffic channels as well as the control channel. You can set up the trunk tags file with individual priorities for tgids so that more important calls will interrupt less important ones. It works pretty well in my opinion :)

RPi4 audio can be interesting... I'm told that you may need to unplug the HDMI cable if you are trying to use the 3.5mm jack, plus I think there is a configuration utility you may need to run to force the sound over a specific port. Get hold of member wgbecks - he can walk you through it.
 

dextergiii

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Thanks boatbod. I leveraged your and the others' expertise on this thread to get the local UDP stream up and running. I was curious to compare preliminary results from OP25 to SDR Trunk. When OP25 is outputting audio, the quality seems really good and I was surprised at the little amount of lag. The video below is a 45min recording reduced to 10min by deleting blank space in between traffic. An echo can be heard along with the spectrum visual when both the Pi and Desktop are locked on the same frequency.


In fairness, it's not an "apples to apples" comparison as I'm using a different antenna, only 1 dongle on the Pi for now, and no prioritization setup.

Do I understand correctly that the whitelist should be used for prioritization and the blacklist to mute traffic?
 

boatbod

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Do I understand correctly that the whitelist should be used for prioritization and the blacklist to mute traffic?
Only one dongle is required or used with rx.py version of op25.

Whitelist and Blacklist are complimentary and have nothing to do with priority.
- blacklist will selectively block individual or ranges of tgid
- whitelist will selectively allow ONLY the individual or ranges of tgids
If you enable a whitelist, all traffic will be blocked unless it is specifically whitelisted.

Priority is controlled by an optional 3rd column parameter in the tgid-tags.tsv file named from trunk.tsv. It's a numeric, defaulting to 3 if unset. Lower number has higher priority, so for example if you set the dispatch tgid to "1" it will take priority over all the other default tgids.
 

dextergiii

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I gotta admit, I was skeptical with the single tuner but adding a few tgid's to a whitelist file resulted in more audible traffic compared with SDRTrunk. Thanks for your help.
 

dextergiii

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@boatbod Now I'm stumped with getting the broadcastify stream up and running. I've been using instructions from https://www.hagensieker.com/wordpress/2018/07/20/op25-raspberry-pi-streaming-part-x/ , from these forums, and from the readme files in the op25 folder, and in no particular order. I was able to get the local udp stream running with very good results, but the stream to broadcastify isn't working. Is there a specific forum post or article which you recommend I reference to go through the configuration process again?
 

boatbod

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@boatbod Now I'm stumped with getting the broadcastify stream up and running. I've been using instructions from https://www.hagensieker.com/wordpress/2018/07/20/op25-raspberry-pi-streaming-part-x/ , from these forums, and from the readme files in the op25 folder, and in no particular order. I was able to get the local udp stream running with very good results, but the stream to broadcastify isn't working. Is there a specific forum post or article which you recommend I reference to go through the configuration process again?
The README-rpi3-liquidsoap is probably the best reference. RR member @wgbecks is also very good at walking people through the setup if you PM him.
 

dextergiii

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Much appreciated boatmod. I was able to get the stream up and running... I made a backup of the files, deleted the op25 folder, and started over with the readme file you mentioned. Thanks for the referral... as it seems I run into challenges with every new milestone I reach lol.
 
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