Software DVB-S demodulator

  • Hi, this has nothing to do with yor CPU, i'm having the same problem. The PlutoSDR uses libiio, which is a piece of software by Analog Devices handling all the USB stuff. but the problem is, that i need to poll the data, which means, that i need to ask it for a new chunk of samples. If i don't manage to do it frequently enough, there are lost samples. And that's the worst thing that can happen for a DVB-S demodulator...

    There are many reasons for this problem. It can be the operating system not scheduling the thread often enough which does the polling. That's the case on high CPU load, or if there are peaks in CPU usage. Of course, this is an important problem, which i need to find a solution for. A temporary solution could be using lower samplerates. That improves things a little, but it doesn't fix the problem. I recommend other SDRs at the moment until i come up with a solution. As far as i know, the PlutoSDR and LimeSDR have this problem. I'll keep you posted on this.

  • hi tony, you have those braces [ ] below the [Generic] line. it won't work that way. change the ui_iqplot line. If oyu want to comment out a line, use the # character at the beginning.

    As an alternative, you can swap the [...] lines. But Generic needs to be the one just above the options.

    perfect thanks it works correct [ to # thanks for your suggestion

    ik1hgi Tony

  • I'm hoping to use DVB-S2 Demod GUI with my Pluto for DVBS-2 on 71MHz and 146MHz. Both my Plutos have been expanded to 70MHz-6GHz (Tested on SDR# so I know they work) but the lowest I can tune my Pluto in DVB-S2 is 325MHz? Am I missing something basic?? If I enter 70MHz before I open the device it then jumps to 325MHz when I do open the device?

    My RTL dongle works as expected but my RSP-1 does not? I thought it was supported?

    Guidance welcome - thanks.

    Gareth G4XAT

  • Hey Gareth,

    I can tell you its works, no problems with the sdrplay-1!!

    see here the solution..


    I have done this for solve the problems with the RSP1

    Install :

    API/HW Driver – v3.04 (9th Jul 2019)

    (now it download the newer version automatic v3.06!!!)

    Instal it in the same map were you placed the DVB-S Demodulater...

    open the map and you will find a "SDRPLAY" map

    Open it...

    Open the map API...There you will find x64 and x86....(64 and 32 Bit pc!!!)

    open the map and find "sdr_play.api and lib"

    Copy both to the dirctory of the DVB-S DEmod

    Greetings ON7KEC - Luc

  • Thanks Luc, that is now working fine :-)

    Just to solve the Pluto tuning range now, although the RSP-1 has slightly better 'ears' than the pluto but it would be nice to have both available.



  • idd Gareth the sdrplay is mutch better than the pluto..

    I'm a little disappointed in the pluto

    The dvb-s2 software runs very good with sdrplay and even rtl stick...buth with the pluto i'ts a other question...

    And it is not Marko's fault , he does a great job of making it works with the pluto also.

    Greetings Luc

  • So this morning I loaded it all onto my I5 Laptop to see if it could cope with low symbol rates, specifically for 146.5 and 71MHz this coming weekend. I've read the original post at the start of this long thread, (VLC URL: udp://@:8888) but although VLC seems to accept the stream ('play bar' bounces backwards and forwards left to right etc) I don't get any video, despite having a good solid data stream (across the shack from Portsdown).

    Am I missing something??



  • I've checked that I CAN decode my signal using my Minitiouner. ALthough the Symbolrate and bandwidth counters are clocking away nicely, sync_confidence is showing 1 and in RED. Buffers is 0/8192.

    I'm getting similar behaviour from a RTL dongle too. Must be something simple I'm missing......

  • hello gareth,

    No problems...i have the same on low sr...even with sync 32 and no buffers...

    by pluto you sould use 2.5bandwidth,no higher...dont work with higher bandwidth.

    the lower sr i have decoded is 66

    Before always problems with decoding...yesterday i have changed the usb cable and take one with 2 ferits and see...the pluto works very good now....strange!!!

    try it and hopely results

  • Hello all,

    tested today dvbs-gui to have a second receiver, seems works well, from 125 up to 1000 K/s. But when I try to receive 1500 the K/s remain at 1200 K/s. When I try to increase the grey band (K/s) remain at 1200, and decode signal at 1500 it's impossible.

    Has anyone experienced some of similar ?


  • Hello Alessio,

    Very simply hihi...

    go to your map from the program

    open the "Config" file...

    Change the line "sr_presets" to..."2000 1500 1000........" and save.

    now you have this.....

    Good luck...


  • Alessio vai al messaggio pubblicato io # 596 che si riceve bene il segnale del beacon

    ciao tony Ik1hgi

  • Dear All,

    First of all I would like to thank Markro92 for this very fine piece of software that allows us to use our SDRs for DATV reception.

    I am having some issues establishing connection between this software and my SDRPlay receiver. The API has already been updated as per ON7KEC's post #604 but it seems like the software fail to set the frequency on the SDRPlay receiver. On the command box (screenshot attached), this is what I notice:

    sdrplay_api_Update sdrplay_api_Update_Dev_Fs failed: sdrplay_api_NotInitialised

    sdrplay_api_Update sdrplay_api_Update_Tuner_BwType failed: sdrplay_api_NotInitialised

    Have been reading through this thread and experimenting with various configurations but it does not seem to help. Any pointers or suggestions are greatly appreciated.

    Thank you.

    73, Sion, 9M2CQC

  • @ Sion,

    With sdrplay you have...i have the version rsp1 and its works very fine.

    Its works direct after the download without the need to install the api .

    in the last version the api is integrated.

    copy the api in your programm...its the only sdrapi here in the directory


    Here its works also with Pluto...not tested with Ethernet.

    But you must use the 2.5Mhz Bandwith higher bandwith give problems to decode

    With the rsp1 i can use the full 8Mhz bandwith

  • @ on7kec

    Where do I get this zip file from? The link that you provided downloads a .exe file instead?

    So now that I have installed this API .exe file - should I uninstall it to avoid conflicting with S2GUI?

  • Hi,

    The zip file is the api from sdrplay that is in my directory from dvb-s software!

    Simply copy that api in your directory of dvb-s software

    see here my directory of the programm

    Disregard the its the file i put here for you...

    Like you see there is only the sdr_api.dll

    This is the original directory of the programm after download and it works for me like this


  • Hi,

    first of all thanks for the program. After initial difficulties with the operation, it works wonderfully.

    Is it possible to connect the RTLSDR via rtl_tcp and the Pluto SDR via network? That would be really good.