RegisterEndpointNotificationCallback causes crash

[beqabeqa473]

Hello.

I am trying to use RegisterEndpointNotificationCallback to get information about device additions/removals

But unfortunately, i am getting a program crash where i am trying to implement it.
Crash dump says
0xc0000005
The thread tried to read from or write to a virtual address for which it does not have the appropriate access.

I wrote the following code:

import comtypes
from pycaw.api.mmdeviceapi import  IMMDeviceEnumerator
from pycaw.constants import CLSID_MMDeviceEnumerator
from pycaw.callbacks import MMNotificationClient

class MyCallback(MMNotificationClient):
    def on_device_added(self, added_device_id):
        #print(added_device_id)

    def on_device_removed(self, removed_device_id):
        #print(removed_device_id)

and then, in the main programm class:

        deviceEnumerator = comtypes.CoCreateInstance(CLSID_MMDeviceEnumerator, IMMDeviceEnumerator, comtypes.CLSCTX_INPROC_SERVER)
        callback = MyCallback()
deviceEnumerator.RegisterEndpointNotificationCallback(callback)

What i am doing wrong? could you please give me a hint?

thanks.

[beqabeqa473]

@Invisi First of all, thank you for example.
I wanted to ask, maybe you know, why on_device_added/removed are not fired when plugging/unplugging audio devices?

thanks.

[Invisi]

Hello there, I just tried that by extending the example with the following code:

    def on_device_added(self, added_device_id):
        print("on_device_added", added_device_id)

    def on_device_removed(self, removed_device_id):
        print("on_device_removed", removed_device_id)

Some things I noticed with a USB soundcard:

• on_device_added did not fire immediately, but only after Windows loaded the necessary drivers
• on_device_removed did not fire at all, not even after manually uninstalling the device via devmgr.msc
• on_device_state_changed did fire when (un)plugging

I'm very much not an expert on Windows' audio shenanigans, but here are my two cents:
If you're trying to build something listening for devices being plugged in/unplugged, try listening via on_device_state_changed with new_state=Active & new_state_id=1 and new_state=NotPresent and new_state_id=4.