No audio from HFP

[david-bouthillier]

My goal is to make a phone call using an embedded device through my Bluetooth connected phone. Playing audio off the phone with the A2DP profile works, but when I trying to make a call, there is no audio.

I tried to play the phone call audio with this script:

alsaloop -C bluealsa:DEV=<my_bluetooth_addr>,PROFILE=sco -P hw:0 -r 8000 -c 2 -f s16_le -n -t 40000 -v

Here is some information about my system. I'm working on a Toradex iMX8MP Verdin board.

root@verdin-imx8mp-15006329:~# tdx-info
Software summary
Bootloader: U-Boot
Kernel version: 5.15.129-6.4.0-devel+git.67c3153d20ff #1 SMP PREEMPT Wed Sep 27 12:30:36 UTC 2023
Kernel command line: root=PARTUUID=c43924ef-02 ro rootwait console=tty1 console=ttymxc2,115200 consoleblank=0 earlycon
Distro name: NAME=“TDX Wayland with XWayland”
Distro version: VERSION_ID=6.4.0-devel-20231220205908-build.0
Hostname: verdin-imx8mp-15006329

Hardware info
HW model: Toradex Verdin iMX8M Plus WB on Verdin Development Board
Toradex version: 0058 V1.1A
Serial number: 15006329
Processor arch: aarch64

root@verdin-imx8mp-15006329:~# bluealsa --version
v4.0.0

root@verdin-imx8mp-15006329:~# bluealsa-aplay -L
bluealsa:SRV=org.bluealsa,DEV=A0:56:F3:97:94:4C,PROFILE=a2dp
    David iPhone, phone, capture
    A2DP (SBC): S16_LE 2 channels 44100 Hz
bluealsa:SRV=org.bluealsa,DEV=A0:56:F3:97:94:4C,PROFILE=sco
    David iPhone, phone, capture
    SCO (CVSD): S16_LE 1 channel 8000 Hz
bluealsa:SRV=org.bluealsa,DEV=A0:56:F3:97:94:4C,PROFILE=sco
    David iPhone, phone, playback
    SCO (CVSD): S16_LE 1 channel 8000 Hz

root@verdin-imx8mp-15006329:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: imx8mpnau8822 [imx8mp-nau8822], device 0: 30c10000.sai-nau8822-hifi nau8822-hifi-0 [30c10000.sai-nau8822-hifi nau8822-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: audiohdmi [audio-hdmi], device 0: i.MX HDMI i2s-hifi-0 [i.MX HDMI i2s-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

root@verdin-imx8mp-15006329:~# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: imx8mpnau8822 [imx8mp-nau8822], device 0: 30c10000.sai-nau8822-hifi nau8822-hifi-0 [30c10000.sai-nau8822-hifi nau8822-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I read the wiki section about SCO routing. When I ran the example I DID NOT hear any audio AND the TX SCO count remained at 0. The last paragraph of that section mentions that audio is not passing from my application to BlueALSA. Can someone help me diagnose this? I did verify that I could play the audio with a simple aplay command, so the sound card is working.

https://github.com/arkq/bluez-alsa/wiki/Using-BlueALSA-with-HFP-and-HSP-Devices#the-sco-routing-issue

Any help is greatly appreciated!

[borine]

I DID NOT hear any audio AND the TX SCO count remained at 0

I'm not sure what you mean by that. Are you saying that there was a call in progress and the phone was sending the audio stream of the call to/from the bluealsa device; and while that was happening you tried something like:

aplay -D bluealsa:PROFILE=sco /usr/share/sounds/alsa/Front_Centre.wav

but the sco TX count remained at zero ?

[david-bouthillier]

@borine Toradex provided me the following command to run to adjust SCO routing. This fixed the audio for the phone call, but the microphone audio is not passed back from the embedded device to the phone.

hcitool -i hci0 cmd 0x3F 0x001D 0x00

Yes, the incoming audio is playing through alsaloop. Here is the full script I run, which includs the command for the mic. There are no errors that I have seen.

alsaloop -g /dev/stdin <<EOF
-C bluealsa:SRV=org.bluealsa,DEV=A0:56:F3:97:94:4C,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=A0:56:F3:97:94:4C,PROFILE=sco -r 8000 -c 1 -f s16_le -n -t 40000 -T 2
EOF

Here is the output of hciconfig -a

root@verdin-imx8mp-15007248:~# hciconfig -a
hci0:	Type: Primary  Bus: UART
	BD Address: E8:FB:1C:CD:E1:64  ACL MTU: 1021:5  SCO MTU: 60:12
	UP RUNNING 
	RX bytes:79973 acl:95 sco:0 events:1829 errors:0
	TX bytes:3443 acl:83 sco:0 commands:117 errors:0
	Features: 0xff 0xfe 0x8f 0xfe 0xdb 0xff 0x7b 0x87
	Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
	Link policy: RSWITCH HOLD SNIFF 
	Link mode: PERIPHERAL ACCEPT 
	Name: 'verdin-imx8mp-15007248'
	Class: 0x2c0000
	Service Classes: Rendering, Capturing, Audio
	Device Class: Miscellaneous, 
	HCI Version: 5.2 (0xb)  Revision: 0x8300
	LMP Version: 5.2 (0xb)  Subversion: 0x1454
	Manufacturer: Marvell Technology Group Ltd. (72)

[borine]

I guess the hciconfig output was taken before running the tests. Are both sco RX and sco TX bytes greater than zero after the test?

If so, and the alsaloop command produced no error messages, then it looks like the mic audio is correctly flowing through alsaloop and bluealsa to the bluetooth adapter.

If sco TX bytes remains at zero, then bluealsa is not sending the audio from alsaloop to the HCI. In that case we would need debug logs from bluealsa to see what is going on. If the TX bytes grows steadily while the test is running, then the error must be in the adapter or the phone.

[david-bouthillier]

@borine here is the output after making a call and then running hciconfig -a

root@verdin-imx8mp-15007248:~# hciconfig -a
hci0:	Type: Primary  Bus: UART
	BD Address: E8:FB:1C:CD:E1:64  ACL MTU: 1021:5  SCO MTU: 60:12
	UP RUNNING 
	RX bytes:182639 acl:104 sco:2134 events:1053 errors:0
	TX bytes:131732 acl:85 sco:2004 commands:114 errors:0
	Features: 0xff 0xfe 0x8f 0xfe 0xdb 0xff 0x7b 0x87
	Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
	Link policy: RSWITCH HOLD SNIFF 
	Link mode: PERIPHERAL ACCEPT 
	Name: 'verdin-imx8mp-15007248'
	Class: 0x2c0000
	Service Classes: Rendering, Capturing, Audio
	Device Class: Miscellaneous, 
	HCI Version: 5.2 (0xb)  Revision: 0x8300
	LMP Version: 5.2 (0xb)  Subversion: 0x1454
	Manufacturer: Marvell Technology Group Ltd. (72)

I could hear audio, but my mic audio wasn't picked up.
There were no errors from alsaloop or in the system log.

[borine]

Well, it is now clear that bluealsa is sending audio to the HCI. So some possibilities I can think of:

• the mic is muted and alsaloop is capturing only silence - check the controls for the card with alsamixer.
• the bluealsa SCO playback pcm is muted and sending only silence - check the controls for bluealsa with alsamixer
• the adapter is not processing SCO data received from the HCI - check with Verdin support
• the phone is not connecting the incoming bluetooth audio to an active call (unlikely !!)

[david-bouthillier]

@borine Thanks so much for your assistance. We ran a test on our mic and it turns out the unit wasn't working!

So if anyone else ends up here in the future, the solution was the following:

• Run hcitool to properly configure SCO packets to be routed over HCI (this command appears to be chip specific)
• Make sure your mic is working!