Mac OSX - I/Q files don't "play"

[Michael Strecke]

A friend of mine uses gqrx (v. 2.9.1 from current DMG file) with a RTL-SDR on a MacBookPro under Mac OS 10.11.6.

Reception and decoding work fine. And recording a I/Q file seems to work as well.

However, playing back this recording doesn't work

I've installed gqrx on my Ubuntu Laptop and I can replay his recording just fine.

These are the steps I took that work on the Ubuntu box but not on the MacBook:
- Tools - I/Q recorder: select file and press play (timer is running)
- Toolbax - Start DSP

On the Linux Box I immediately see a spectrum and the waterfull.
On the Mac nothing happens except that the fans start to spin up suggesting at least some kind of increased activity.

Any suggestions what I might have missed?

Thanks

Mike

[Alexandru Csete]

Hi Mike,

I did a quick test and it does work for me on a Mac... But it is a bit
wacky functionality that never got properly integrated for various
reasons.

I recommend that gqrx is running using a dongle (DSP enabled), then
activate the IQ play.

Alex

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[Michael Strecke]

Hi Alex,

Thank you for your suggestion.... It didn't work.

I activated the Activity Monitor and compared the CPU load in different situations:
- the load when starting the I/Q file playback is negligible
- when starting the DSP it jumps to approx. 70%
  (however nothing is shown in the displays)
- when performing a DSP of a live signal it shows 140% - i.e. approx. double the load
  (with spectrum and waterfall display)

We know that the MacBook is powerful enough to perform a DSP.
We know that it is doing something when trying to decode the file playback.

Any chances that parameters in the "Configure I/Q device" panel may interfere?

Thanks

Mike