Software DVB-S demodulator

  • @markro92 Great Software, But it seems DVBS1 is not working anymore..


    Tested on 3 different locations with different computers and setup's

    Tested on 144.600, 436 Mhz and 1255mhz.


    Use RTL stick as receiver.

    DVBS2 works simple and perfect.

    250 KS up to 2Ms..


    But switching to DVBS1 i get the constalation perfect but no sync..

    not even more than 1.


    I use 500KS FEC 2/3 DVBS1 H264... for testing...


    Can you confirm that DVBS1 should work?


    Best regards...

    Benno




  • Works for me :)

    Tested with 'Antenne Düsseldorf' TP on Astra 3B @ 23,5°E.

    FEC 7/8


    Well the thing is, DVB-S1 is horrible to use at the moment, because it's kinda unclear.

    Version 2.0.21 will finally have blindscan, but until then:

    Set the FEC, and then click on "DVB-S1 Symbol Skip", and combine that with rotating the constellation with the Derotate slider. There is only one combination that works. SO you basically click a few times onto the skip button, if it doesn't work, rotate the constellation 90 degrees and skip symbols again until it works. In that case the sync_confidence value will go up and stay high without flickering.

  • So, an update on higher symbol rates, no luck with QPSK 9/10 on 27500 and 29500 MSym/s samples. Constellation looks noisy and nothing seems to be succesfully decoded although there are locks sometime.
    Any advice what could be better tweaked? Also, is there a frequency offset debug info hidden somewhere?


  • Hi, there are a few things, maybe there is an error calculating filter coefficients, can you change the symbolrate slightly? maybe to 29501?

    This is clearly a problem with timing recovery or earlier stages than that. Can you also try to increase the input gain? it seems very low. The FFT should atleast be yellow-ish. btw, there is no frequency offset info, but that's not the problem here. I did a lot of optimizations to reduce CPU load, i could give you a new version tomorrow. But don't expect too many new features yet.