First, look at this audio waveform: audio waveform from Audacity

Now, I tell you what it is: After connecting a Sony CECHYA-0076 with a TPLink UB400 Bluetooth adaptor in Debian Buster, using BlueZ and Blueman, finally get/send audio with Pulseaudio using ofonod and ofono-phonesim... I record my voice into Audacity. And this is what I got. You can hear here.

The problem is not a hiss in the background (maybe there it is), is not a buzz, also if the sample rate and bits depth are low, I will understand: this device is made for phone calls. The problem is, as you can see in the screenshot, some kind of "loss of data" or bad encoding. They make the audio almost inaudible, totally broken and full of noise. Maybe, after some seconds, the noise is reduced... but then, it stars again.

I tested this handsfree with my mobile phone and it works Ok, the other person listened to me well.

Before you suggest:

  • As far as I know, this device doesn't work with A2DP, that's why I had to install and run ofono and ofono-phonesim. The only card profiles are "headset_head_unit" and "off". Anyway, I need to use the microphone, so A2DP would not be the right profile.
  • I tried to set the headset-input latency offset to a high number ($ pactl set-port-latency-offset <bluez_card> headset-output 125000 or 500000) without any difference.

pactl list (only card)

Placa #2
    Nombre: bluez_card.00_22_A6_47_29_87
    Controlador: module-bluez5-device.c
    Módulo dueño: 24
        device.description = "Wireless Headset"
        device.string = "00:22:A6:47:29:87"
        device.api = "bluez"
        device.class = "sound"
        device.bus = "bluetooth"
        device.form_factor = "headset"
        bluez.path = "/org/bluez/hci0/dev_00_22_A6_47_29_87"
        bluez.class = "0x200404"
        bluez.alias = "Wireless Headset"
        device.icon_name = "audio-headset-bluetooth"
        device.intended_roles = "phone"
        headset_head_unit: Headset Head Unit (HSP/HFP) (sinks: 1, sources: 1, priority: 30, available: yes)
        off: Apagado (sinks: 0, sources: 0, priority: 0, available: yes)
    Perfil Activo: headset_head_unit
        headset-output: Headset (priority: 0, latency offset: 125000 usec, available)
            Part of profile(s): headset_head_unit
        headset-input: Headset (priority: 0, latency offset: 500000 usec, available)
            Part of profile(s): headset_head_unit

I connected it with ofono using this tutorial.


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