raw I/Q channels

brianbrian
in Problems and Issues
Where can I find the documentation for the I/Q channel mode for external decoders?

Reading the doc and information suggests that even raw I/Q might be compressed. Is this true?

Thank you.

Comments

  • jksjks
    IQ mode is never compressed (would defeat the purpose). The thread discussing the initial DRM successes is here: http://forum.kiwisdr.com/discussion/899/drm-demod-yes-external-app-dream-now-working

    There are links to YouTube videos showing DRM decoding using Dream and SoDiRa on kiwisdr.com
  • jksjks
    edited October 2018
    I should add: The biggest pain seems to be setting up the necessary software to route audio between the browser and the decoder application. It's been talked about but there is no setting currently on any browser that says "route the audio output from anything running inside the browser (e.g. YouTube, Kiwi, etc.) to another application (or a virtual audio connection directly in the OS). Decoder programs (fldigi, MultiPSK, Dream, SoDiRa, etc.) all allow you to select from virtual audio connections if they find them on startup.

    The other problem is that the best and easiest to use seem to cost money. I don't much about Windows but on the Mac I struggled for a long time with free routing software that was buggy and ultimately didn't survive an OS upgrade. Eventually I skipped a few trips to the pub and shelled out US$100 for software called "Loopback" which works flawlessly and is routinely updated. Highly recommended.
  • brianbrian
    I was a bit surprised when I thought I saw that the I/Q stream was compressed. That was a "WTF" moment. It did seem to me like that would defeat the purpose. If you have the raw I/Q stream you can do almost anything.

    I don't use windows. Everything I have is either Mac or Linux. Perhaps I am naive but I wasn't expecting to connect from a browser to get the I/Q stream. I thought there would be a UDP port that would have the stream on it and perhaps a TCP port to which we could send a frequency command. After all, I don't need to render the waterfall or anything else. I just need to set the frequency and then suck up the samples. Something like that would make it easier to interface to GnuRadio too, and then people could make just about any radio they want using the KiwiSDR as a front-end.

    I am familiar with VAC on the PC (played a lot with HPSDR). Loopback looks like it does the same thing for Mac. So I presume that the I and Q channels appear as L and R channels of a stereo stream?

    Thank you.
  • jksjks
    When you mentioned "external decoders" I assumed you were interested in I/Q obtained from the L/R channels of the browser audio output, e.g. so the browser could be used to control the Kiwi. It is indeed possible to connect over the network (via web sockets) to the Kiwi server and issue the same API commands as the browser UI does to set frequency etc.

    An example written in Python that works on Linux/OS X is called kiwiclient/kiwirecorder available here: https://github.com/jks-prv/kiwiclient/tree/jks-v0.1 It is capable of recording to .wav files but there is no reason you couldn't stream to another application. I think Christoph was working on (or has working) an interface to GNUradio this way. The I/Q mode bandwidth is of course limited to the audio channel bandwidth (currently 12 kHz).
    ChrisSmolinskiKA7U
  • brianbrian
    Bingo! That is precisely where I wanted to go with this. 12kHz I/Q is fine because I can use multiple KiwiSDRs to monitor as many narrow-band channels (12kHz or less) as I want. I have a need to receive and decode many channels concurrently.

    Thank you.
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