[alsa-devel] [pulseaudio-discuss] Problem with timing and USB scanning...

[Raymond Yau]

>
> Howdy! I have a situation where PulseAudio is "grabbing" a usb headset
before
> fully initialized, thus not all features are being recognized.
>
> More details here:
>
>
https://askubuntu.com/questions/537166/usb%2daudio%2ddevice%2dnot%2dfully%2dworking%2dafter%2dhotplug

You have to post output of alsa-info.sh and pactl list before and after the
hot plug

This look like priority issue if you have usb web cam mic and hotplug usb
headset

https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/sound/usb/mixer.c?id=9fcd0ab130579d9742538340edda3225f2b49a3e

Another issue is some usb devices only obtained dB scale at a later time
after the control is created

This may need some delay for pulseaudio to get dB scale

You can add printk statement to find out how much time you need

>
> and a related, I think, bug here:
>
> https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/841433
>
> Anyone have a pointer to a udev rule I could create (or a PulseAudio
config I
> could  tweak) that would case a delay before the device is scanned by
> PulseAudio?
>
> I'm pretty sure it's a timing issue, because:
>
> Works OK:
> Cold boot (or reboot)
> Resume from hibernate
> Resume (or hotplug) -> killall/restart pulseaudio
>
> Fails to work:
> Hotplug
> Resume from sleep
>
> Any tips?
>