I followed this tutorial to connect and play audio over bluetooth - How to Setup Bluetooth Audio Profiles (Linux) | Toradex Developer Center
Everything works until I get to the last step with Hands Free Phone calls. I initiate the call, but audio is never played through the speakers on my device. I’ve tried 4 different phones (Android & iPhone) but none seem to work.
This is the error message I get in the console
underrun for playback bluealsa:SRV=org.bluealsa,DEV=74:9E:AF:12:A2:04,PROFILE=sco
System Information:
root@verdin-imx8mp-15006329:~# bluealsa-aplay -L
root@verdin-imx8mp-15006329:~# aplay -l#0: subdevice #0 #0: subdevice #0
root@verdin-imx8mp-15006329:~# arecord -l#0: subdevice #0
root@verdin-imx8mp-15006329:~# tdx-info
Bootloader: U-Boot#1 SMP PREEMPT Wed Sep 27 12:30:36 UTC 2023
Hardware info
HW model: Toradex Verdin iMX8M Plus WB on Verdin Development Board
Additional Information:
When I added -v to the alsaloop command, this is the output I received:
root@verdin-imx8mp-15006329:~# ./alsa-call.sh
Hello @david.bouthillier ,alsaloop -v, we can see that it failed to open the playback device:
plughw:0,0 open error: Device or resource busy
Usually, when this happens there’s something else in the system already using that resource. Could you check if there are other processes doing anything with sound?
You can try to do that with fuser:
fuser /dev/snd/*
If that doesn’t show any result, and you know other alsa commands are working on your device (you can play audio with aplay for instance), please let us know.
Best regards,
Hi Rafael,
Thanks for the help.
I ran fuser /dev/snd/* before and after attempting the hands free phone call. In both cases, the result was empty.
And yes, I verified that I can play a wav file using aplay
Also for clarification, I can get audio to play when in the A2DP role. Music from Spotify on my phone is played through the speaker on the device.
I can reproduce this issue here. After some investigation, I could get a partially working setup doing the following:
# setup sending sco data through host interface (hci)
hcitool -i hci0 cmd 0x3F 0x001D 0x00
alsaloop -g /dev/stdin <<EOF
-C bluealsa:SRV=org.bluealsa,DEV=<connected_bluetooth_mac>,PROFILE=sco -P plughw:0 -r 8000 -c 1 -f s16_le -n -t 40000 -T 1
-C plughw:0 -P bluealsa:SRV=org.bluealsa,DEV=<connected_bluetooth_mac>,PROFILE=sco -r 8000 -c 1 -f s16_le -n -t 40000 -T 2
EOF
But with this, I only get audio coming from the device, but cannot get microphone data out.
I reached this state by reading this excellent page:
It includes lots of information about the potential pitfalls of hands-free profile use.
Is the hands-free use case with a microphone required for your application?
I’m glad to hear that you can reproduce the issue!
Yes, a microphone is critical to our product.
I can confirm the hcitool command fixes the audio portion of the call.
Have you had any luck getting the microphone to work?
Unfortunately, I didn’t have time to continue the investigation, and I’ll probably not be able to come back to it in the next few days.
Hi Rafael. Could you point me to where you found the documentation for the HCI commands for the Azurewave chip? Thanks!
Sure, I found it on the UM11490 document from NXP:Feature Configuration Guide for NXP-based Wireless Modules on i.MX 8M Quad EVK - User manual
You’ll have to have an account with NXP to download it from this link.
Hi @rafael.tx ,
Good news, it turns out the mic I was using was broken
One question though, is the HCI command something the Bluez driver should be doing, or PulseAudio perhaps? Or should our application run this command?
Great! I guess mine must have some problem as well… I’m glad it worked now.
One question though, is the HCI command something the Bluez driver should be doing, or PulseAudio perhaps? Or should our application run this command?
According to here , bluez-alsa does that for some broadcom BT modules where they could find definitive documentation about the correct command. For the TI modules they aren’t sure it will work for all modules, so they don’t do it automatically.
I guess something similar is going on here, either not a lot of people uses the NXP modules to have asked specifically for that, or the developers didn’t have access to the documentation.
1 Like
eric.tx
September 17, 2024, 6:52pm
14
Hey @david.bouthillier ,
It’s been awhile. Have you found a solution/work around to this topic?
Our team has been able to add pluseaudio and webtrc to to try as an alternative method. This can successfully build, but there does still pose some audio issues that may need some effort to fix. Is this something you would be interested in?
-Eric
So running the hcitool command is the fix in our situation.