Software DVB-S demodulator

  • @SWL - markro92


    Hello Marcel,


    I did reception tests with the 2.0.20-version today and they all were very successful. Once I found the right adjustments, I was able to jump to another stations frequency, change the bitracte and wait a few seconds and the signal was there. Sometimes, changing the bitrate up or down by one bit helps to find synchronization quicker. Great job, thanks!



    I have two request respectively questions:


    1st: would it be possible to allow the L.O. frequency to be entered with a few digits behind the comma? I use a LNB with a 26 MHz GPS-controlled oscillator and my L.O. frequency actuall is 9388.888 MHz. But I can only enter freq_lo0 = 9389.


    This would help to quicker enter the right frequency.



    2nd: when I try to change the IF frequency with the scroll whee of my mouse it changes the frequency in MHz steps. Is that anything that has to do with my computer or is it something in your software? I would be able to change the frequency in smaller steps, actiually, for example like 100kHz.




    Thanks and vy 73


    Holger 'Geri', DK8KW

  • This new version seems very stable, congratulations on a great job SWL - markro9 !



    I was hoping it could receive at 5700-5800 MHz but it was not possible.

    It only receives up to 4295 MHz then suddenly a signal completely absent on the spectrum! Why, it seems more a problem of calculation than of the sensitivity of the radio. I used two Adalm Pluto with F5OEO firmware both in Tx and Rx.

  • Ok, sorry for not finding the issue earlier, i'll look into it. There are a few spots in the code that i could have overlooked. Is it just the FFT display? The actual reception should work if you rightclick and try to find the transponder by accident while only using the IQ plot. Not sure if you know what i mean. FFT is bugged, rest should work as is. I'm sure that i fixed the calculation of filter coefficients, so reception should be fine regardless.

    You are correct with 4295MHz. To be exact, the maximum frequency seems to be 2^32-1 (two to the power of 32), which is 4294967295Hz.

  • Just playing about with the latest version, the beacon is a lot easier to receive but any other feed so far in the last 20 mins I've been trying is imposable to get video with even though I see the callsign in the spectrum etc. Maybe vlc player can not decode H.265 video ?

  • Ok, sorry for not finding the issue earlier, i'll look into it. There are a few spots in the code that i could have overlooked. Is it just the FFT display? The actual reception should work if you rightclick and try to find the transponder by accident while only using the IQ plot. Not sure if you know what i mean. FFT is bugged, rest should work as is. I'm sure that i fixed the calculation of filter coefficients, so reception should be fine regardless.

    You are correct with 4295MHz. To be exact, the maximum frequency seems to be 2^32-1 (two to the power of 32), which is 4294967295Hz.

    Thanks for the reply and for your precious commitment. You are doing a fantastic job!

    I don't look at the waterfall, I tune the numerical frequency to tune.

    I await the correction with much hope and gratitude! 73 de Luigi IZ7PDX JN80ps

  • M1CTK: do you have an AMD CPU and is is crashing?

    It should run on AMD CPUs, but i'm not able to test it. I'm only using instruction sets at the moment supported by both CPU families.

    Can you give ne a screenshot of your titlebar if the program starts up? otherwise Download CPU-Z and give me a screenshot of the first window, where CPU Name and Feature Flags are displayed. It should support up to SSE4.1. Of course i also want people with recent AMD chips to run this.

  • M1CTK: do you have an AMD CPU and is is crashing?

    It should run on AMD CPUs, but i'm not able to test it. I'm only using instruction sets at the moment supported by both CPU families.

    Can you give ne a screenshot of your titlebar if the program starts up? otherwise Download CPU-Z and give me a screenshot of the first window, where CPU Name and Feature Flags are displayed. It should support up to SSE4.1. Of course i also want people with recent AMD chips to run this.

    It's someone I know who has an AMD, my i7 on a 2012 mac mini works much better with the latest version as the video shows. If there could ever be some kind of blind scan added as demod is very much more useable now. Great work

  • great piece of Software !


    when I connect the Pluto via Ethernet, it is found and displayed in the device list.


    If I connect i.e. the SDRplay via USB, the device is not found. The SDRplay works with SDRconsole on the same machine. Also if I connect the Pluto via USB it is not found.


    Are there any special settings in order to work with USB devices ?


    vy 73, Kurt

  • Hi SWL - markro92,

    First I would like to commend you on the application, seems quite a lot of work you invested in there!
    I'd like to try it out with recorded DVB-S2 SAT-TV signal (usually 22-29,7 MSym/s).

    I have the raw I/Q sample files and feed them to the app via simple TCP server python application.

    However, the app stops at 20 MSym/s setting so no luck there.

    Is it possible you can expand that setting up to 30 MSym/s?

    Thanks!

  • Hi, you can do that yourself in the config file. There is a setting called 'sr_max'. You can also edit the presets there.

    However, right now even 10MSym/s is ambitious. I've received tv feeds with 9600ksym/s before. It works with high SNR, otherwise demodulating and LDPC decoding takes too long. I'm partially rewriting the demodulator at the moment. There is a lot of potential when it comes to optimizations, but 30MSym/s seems out of reach for a software-only solution (I'm not saying it's impossible). By the way, thanks for your kind words :)

  • Great, thank you for the fast reply!

    I seem to get a lock and the channels are read, so I suppose it's doing quite alright with this symbol and sample rate :)

    However VLC reads nothing on the 8888 port. Can I somehow save the ts output to file?

  • Hi, for performance reasons, you could try to reduce the number of RRC taps to 32, and disable the update of CMA coefficients. That's the Update coeff. checkbox on the right. Can you show me the statistics view? Click on Debug -> Debug Worker Stats.

    Glad it seems to work. how fast do buffers fill on the bottom right of the window? which CPU model are you using?

    Looks promising :)

    You can save the output by clicking on the 'File' button in the 'Network / Network' section. It will ask you for a location and filename.

    Alternatively, streaming is right below that. UDP / TCP are supported. VLC URLs are for example for UDP: udp://@:8888 or for TCP: tcp://127.0.0.1:8888

  • You can save the output by clicking on the 'File' button in the 'Network / Network' section. It will ask you for a location and filename.

    Alternatively, streaming is right below that. UDP / TCP are supported. VLC URLs are for example for UDP: udp://@:8888 or for TCP: tcp://127.0.0.1:8888

    Got it! It confused me that it didn't start saving to file until I click on it while the acquisition is running.
    (And streaming works as well).
    Thank you, awesome work! :)

  • Ok, very good :) nice CPU. Maybe i should upgrade, too. Still have a good old Haswell CPU (5820K).

    In this case, i really think 30MSym/s should also be doable. Thanks for the feedback :)

    Which SDR are you using by the way?

    Edit: Intel says you have a Mobile CPU? is that true? I feel my PC is running on a potato right now :D

  • Ok, very good :) nice CPU. Maybe i should upgrade, too. Still have a good old Haswell CPU (5820K).

    In this case, i really think 30MSym/s should also be doable. Thanks for the feedback :)

    Which SDR are you using by the way?

    Edit: Intel says you have a Mobile CPU? is that true? I feel my PC is running on a potato right now :D

    Will try with 30 MSym/s and let you know the results :)

    The samples were recorded with Ettus X310 (UBX-160).
    Tried with limeSDR mini but hit a lot of walls (may try again connected directly to this software).

    As per the CPU, well my Dell laptop is mobile if that's what they're referring to :D