Phone audio crackling and popping

[robt]

I hav OAP installed on a CM4. Everything is working perfectly except when I make or receive a phone call all I hear is crackling and popping. I can't hear any ringing or anyone talking it just continues to pop and crack.

I am using a TP Link CSR BT 4.0 Adapter, ugreen sound card.

I have tried fresh install and a different phone and it still does the same thing.

It is the only thing not working for me and I would really like to solve it.

Thanks.

[Daniel_BlueWave]

Check these:
https://bluewavestudio.io/community/thre...l#pid13069
https://bluewavestudio.io/community/thread-3220.html
https://bluewavestudio.io/community/thread-3672.html

[robt]

Check these:
https://bluewavestudio.io/community/thre...l#pid13069
https://bluewavestudio.io/community/thread-3220.html
https://bluewavestudio.io/community/thread-3672.html

Thanks. I have done all that and the problem still persists. The audio is fine everywhere else. But as soon as a call comes through it is crackling and popping and goes fine after the call ends. I have a ground loop isolator as well and a constant 5A power supply. I have searched for my issue and cannot find anything that is an exact match. The noise is not alternator noise. It almost sounds like it keeps trying to output audio but makes cracking sounds instead.

I have also tried another TP Link Bluetooth adapter and it is also doing the same thing.

[robt]

I have tried changing the following in default.pa to 0, 1 and 2 and there is no change.

load-module module-bluetooth-policy auto_switch=0

I have just tested with a Pi 4B and the problem is not there. I have also tested with two CM4 and the problem is there on both. Any ideas on what may be causing this?

[robt]

I have managed to find the solution. And I will update here for anybody using a compute module 4 (CM4) in the future.

USB is disabled on CM4 by default and needs to be enabled in the config.txt file.

The datasheet and most guides online say to do this by adding the following line to config.txt:

dtoverlay=dwc2,dr_mode=host

This is what was causing my issues.

Instead use this line to enable USB: 

otg_mode=1

After doing this, calls are working fine.

[Daniel_BlueWave]

Great finding. Thank you for the feedback.

[FortunyPT]

I have managed to find the solution. And I will update here for anybody using a compute module 4 (CM4) in the future.

USB is disabled on CM4 by default and needs to be enabled in the config.txt file.

The datasheet and most guides online say to do this by adding the following line to config.txt:

dtoverlay=dwc2,dr_mode=host

This is what was causing my issues.

Instead use this line to enable USB: 

otg_mode=1

After doing this, calls are working fine.

It looks like you just solved the problem that has been making me scratch my head for the last 4 months now... with a simple line of text!

I've been trying out different USB dongles and pulse-audio configs to no avail, I'm glad that everything works fine now!

After some digging, it seems like when using:

dtoverlay=dwc2,dr_mode=host

The USB controller chosen is an older one that apparently doesn't support the hands-free profile of any adapter that I tested.
I guess It's pretty easy to find what is causing the problem once you know what the solution is. 


Thank you for sharing your finding, it will defiantly help others who are running the CM4 too!