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Re: [Discuss-gnuradio] Audio source cannot use 2 outputs (Stereo) in win

From: Gary.Simpkins
Subject: Re: [Discuss-gnuradio] Audio source cannot use 2 outputs (Stereo) in windows
Date: Sun, 5 May 2019 10:39:31 +0100
User-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

Hi Marcus and any windows experts

Trying to get portaudio working in GNURadio (win10). can you answer these simple questions.

Using  gnuradio-config-info  --enabled-components, I get the following.

python-support;testing-support;volk;doxygen;sphinx;gnuradio-runtime;gr-ctrlport;gr-blocks;gnuradio-companion;gr-fec;gr-fft;gr-filter;gr-analog;gr-digital;gr-dtv;gr-atsc;gr-audio;* portaudio;* windows;gr-channels;gr-noaa;gr-pager;gr-qtgui;gr-trellis;gr-uhd;gr-utils;gr-video-sdl;gr-vocoder;gr-fcd;gr-wavelet;gr-wxgui;gr-zeromq.

 Is the * infront of portaudio significant?  Is it a wild card? do you now what this means? (I know this is windows and not UNIX)

gnuradio-config-info  --userprefsdir  responds with


In this directory is a config.conf file.  It was empty, so I added


audio_module = portaudio

I saved and restarted the PC, but GNUradio is not using portaudio. So it looks like it is not being used.



On 04/05/2019 14:39, Müller, Marcus (CEL) wrote:
Hey Gary,
please keep things on the list! Good news:
That's the exact opposite of what I wanted to convey! *Use* GNU Radio's
existing portaudio interface; chances are that your GNU Radio
installation supports that (which is why I asked how you've installed
https://www.gnuradio.org/doc/doxygen/page_audio.html tells us how to do
you just need to find your GNU Radio configuration (for me as Unix user
it's in ~/.gnuradio/config.conf, but yours is probably somewhere else;
running `gnuradio-config-info --userprefsdir` should give you an idea
where to look). Add, if not already in there, the following:

audio_module = portaudio

Done! That tells GNU Radio to not just try the first best guess of what
audio system you want to use (that being windows API under windows),
but to specifically use portaudio – and that should have the features
you're looking for.

Still, the windows source not working as it should is a pain. We should
fix that.

Best regards,

On Sat, 2019-05-04 at 08:05 +0100, address@hidden wrote:
Many thanks for the explanation. Looks like I can go no further. I do
not have the skills to develope the audio source.


Sent from my Huawei Mobile

-------- Original Message --------
Subject: Re: [Discuss-gnuradio] Audio source cannot use 2 outputs
(Stereo) in
From: "M黮ler, Marcus (CEL)"
To: address@hidden,address@hidden

Hi Gary!

I have double checked and all the windows audio devices I have
for the audio source are 2 channels.
I never doubted that – all I wanted to point out that the I think
was Windows that told the GNU Radio windows audio source it saw
one channel, and consequently the windows audio source only enabled
output port.

I was wrong, it turns out! When you look at gr-
audio/liob/windows/windows_source.cc, you'll find the number of
streams of the block to be hardcoded to be between 1 and 1, so...

windows_source::windows_source(int sampling_freq,
const std::string
: sync_block("audio_windows_source",
io_signature::make(0, 0, 0),
io_signature::make(1, 1,

The last line does that.
So, that's a um, underdeveloped feature in the windows audio

They work fine with WSJT-X, or MAP65.

The stereo channels I wish to use are the I and Q outputs from
SDRPLay Duo using virtual cables

(I have tried the speaker outputs from the PC with GNURadio audio
and get the same problem)

Does the audio source work with two channels on linux?
Yes, (haven't tried today, but it /used/ to work), but it sadly
nearly no code with the windows audio source. That's due to fact
Linux' ALSA and Windows' sound API and OS X's Core Audio are pretty

I do have an idea, though, which *might* be a solution to your
but: untested; don't expect wonders.

Has your GNU Radio build portaudio enabled? As said, it's not
but unlike the windows audio source, the portaudio source at least
the state of the source code (far as I can tell) enables as many
maximum output streams as your card has.
I am using the latest version of GNURadio on a 64bit win

Built from source, or where did you happen across it?

I am really stuck here. Nothing I try allows the second output to

Sorry to hear that! We'll try to get you unstuck :)

Best regards,

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