# Manage INVALID HANDLE channel correctly
**URL:** https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277
**Category:** FMOD Engine
**Tags:** cpp
**Created:** [June 2, 2023, 1:15pm UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277 "2023-06-02T13:15:46Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@richarrr](https://qa.fmod.com/u/richarrr)
#### Post date: [June 2, 2023, 1:15pm UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/1 "2023-06-02T13:15:46Z")
Hi,
Here is my scenario:
First I call playSound, this creates a ‘Channel\* chan’ object.
Let’s say after a few seconds, I want to modify something on ‘chan’ ( modify frequency, fade out, stop … ).
My concern is that if the sound has already finished playing it seems FMOD will automatically delete the ‘chan’ object. And all my calls on ‘chan’ will return error with ‘FMOD\_ERR\_INVALID\_HANDLE’.
My questions:
When I use my invalid ‘chan’ handle. Does FMOD means:
“I know this is a channel handle that has stopped, so I won’t modify it”
or
“I don’t know what ‘chan’ is, it musn’t be used in the API anymore”.
in other words, is it illegal to use an invalid ‘chan’ ( like using a deleted object in C++ ) ?
If it’s illegal, what’s the easiest way to track if my ‘chan’ is still valid, I need a way to set it to ‘nullptr’ when FMOD deletes it internally.
Thanks
* * *
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### Author:  [@andy55](https://qa.fmod.com/u/andy55)
#### Post date: [June 5, 2023, 2:48pm UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/2 "2023-06-05T14:48:06Z")
Hi,
I’m relatively new to FMOD too and found this confusing as well.
I mention [here](https://qa.fmod.com/t/sound-callbacks-in-ios-background-mode/20256) about using [ChannelControl::setCallBack()](https://www.fmod.com/docs/2.02/api/core-api-channelcontrol.html#channelcontrol_setcallback) to get a callback when the sound ends so maybe that works for you. As I mentioned, I am still trying to figure out why it is not firing when iOS is in background mode.
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### Author:  [@richarrr](https://qa.fmod.com/u/richarrr)
#### Post date: [June 5, 2023, 3:57pm UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/3 "2023-06-05T15:57:44Z")
Thanks for the reply -
yes I had the idea of adding callback for each sounds I wanted to track. but that feel a bit over-engineered. I hope there is something simpler
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### Author:  [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)
#### Post date: [June 6, 2023, 4:16am UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/4 "2023-06-06T04:16:22Z")
Hi,
I will link to our white papers that outline our handle system: [FMOD API | White Papers - Handle System](https://www.fmod.com/docs/2.02/api/white-papers-handle-system.html). In summary, it is closest to your first answer but not exactly. As it says in our docs “If a Channel is stopped with ChannelControl::stopor ends naturally, the Channel handle will become invalid and return `FMOD_ERR_INVALID_HANDLE`” so it will be safe to still interact with it however, it will just return an invalid handle. A way to check if a channel is still valid is using the channel in an FMOD function and checking the result for `FMOD_ERR_INVALID_HANDLE`.
Hope this clears it up a bit.
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### Author:  [@richarrr](https://qa.fmod.com/u/richarrr)
#### Post date: [June 6, 2023, 7:30am UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/5 "2023-06-06T07:30:57Z")
Thanks for the detail.
So my understanding is that on my app side, I don’t need to track the life time of all my channel handles. There is no risk of undefined behavior when using an invalid one.
That makes my developer life easier.
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### Author:  [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)
#### Post date: [June 7, 2023, 6:13am UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/6 "2023-06-07T06:13:45Z")
Correct, if a stopped channel is used in an FMOD function it will return the `FMOD_RESULT` `FMOD_ERR_INVALID_HANDLE`.
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### Author:  [@richarrr](https://qa.fmod.com/u/richarrr)
#### Post date: [June 7, 2023, 7:57am UTC](https://qa.fmod.com/t/manage-invalid-handle-channel-correctly/20277/7 "2023-06-07T07:57:52Z")
Thanks for the confirmation