Sampling rate with Bluetooth speaker

[Rick, W4XA]

Howdy all, 

I have discovered that I can use my JBL Charge-3 bluetooth speaker as a connected speaker using the Macbook Pro (Monterey) and my older Macbook Pro running KDE Neon (Ubuntu Linux)  For some reason, the mic doesn't work at all with the MacOS macbook but surprisingly it does work well with the MacBook running Linux (go figure) 

When I launch FreeDV, and select Audio Config, both the speaker and microphone are reported with an sampling rate of 8000.

If left alone, FreeDV will report that 8000 is "less than 16000"  which I suppose is the minimum sampling rate for operation.

When I select the speaker for playback, I manually enter a sampling rate of 44100 or 48000 and it works just fine until I stop the program then the sampling rate for the speaker (and mic) goes back to 8000.

Is there a way I can get FreeDV to save the manually entered sampling rate permanently?

Regards, 

Rick

[Mooneer Salem]

Hi Rick,

There are a few things going on. First, for RADE, we prohibit use of sampling rates under 16 kHz as the audio quality takes a nosedive if 8 kHz sources are used. 

Second, Bluetooth devices always downgrade to the lowest supported sample rate when the transmit side of the device's used. This is a technical limitation of BT, unfortunately. Fortunately, this is usually 16 kHz or above so FreeDV is typically able to use BT headsets (just not the one you're trying to configure).

Anyway, sorry I don't have a better answer for you. Let me know if you have any other questions.

Thanks,

-Mooneer K6AQ

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[Rick, W4XA]

Thanks for that explanation Mooneer.

It does actually work but I have to manually set the sampling rate every time I start the program.  I was shocked that it worked at all!

I just tried it as a test and was pleasantly surprised!  I would like it to "save" the setting though!

For some reason, I cannot get the Mid 2012 Macbook running Linux to use the internal mic but it works with a USB mic and that JBL BT speaker!     I'll keep testing though!

Thanks again!

Rick