Why is different channel totals in unified audio example flagged?

[EdSutter]

The usb_device_descriptor.h file for both of the usb_device_composite_hid_audio_unified examples in the SDK has a preprocessor line that catches the case where  AUDIO_IN_FORMAT_CHANNELS != AUDIO_OUT_FORMAT_CHANNELS.

But then the comments in the error say:

/*default in channel and out channel are same, if the channel setting is different, please remove this error manually, then check the AUDIO_FORMAT_CHANNELS. */

The AUDIO_FORMAT_CHANNELS definition isn't used anywhere, so there's nothing to check.  Plus it appears that 'IN' and 'OUT' versions of these definitions are used appropriately in the code.  So, what is the point of this check?  Is it illegal for some reason to have a different number of input channels than output channels? 

[FelipeGarcia · Accepted solution]

Hi Ed,

I have received response from internal team, it seems this error was added just for simplicity but there is no restriction about this in USB Audio spec.

This restriction is only for the usb_device_composite_hid_audio_unified demo. The SDK considers simplifying the design of the application when developing the demo, so this restriction is added.

There are no restrictions on this in the usb audio specification.

Best regards,

Felipe

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[FelipeGarcia]

Hi Ed,

I agree with you that the comment about checking AUDIO_FORMAT_CHANNELS does not make sense as it is not used, please give me some time to check this internally and will let you know.

Best regards,

Felipe

[EdSutter]

Felipe,

I am getting an email asking me to mark something as the solution, but I am assuming you will be getting back to me with an answer, correct?

Ed

[FelipeGarcia]

Hi Ed,

Don’t worry, those are automatically generated emails by the community. I have contacted internal team to get confirmation about this issue.

Bes regards,

Felipe

[EdSutter]

Felipe,

Thanks... I've been running for a week or so with different IN/OUT channel counts and things seem to be fine; but it would be nice to hear this officially.  

Awaiting your reply...

Regards,

Ed