app_bricks/audio-classification: allow to disable the microphone initialization

[stefanotorneo]

We need a way to disable microphone initialization when the user doesn't require it, but wants to classify an audio file.

[robgee86]

I understand the need, but maybe we have some alternatives:

• We could make the microphone really optional, None would mean "don't instantiate a default microphone". This would be a bit awkward with respect to other APIs that treat None as "instantiate a default microphone"...
• We could make the classify from file feature a static function of the brick. I remember there are some dependencies on self that are required, probably related to EI. Can we find a workaround for that?

[stefanotorneo]

I understand the need, but maybe we have some alternatives:

• We could make the microphone really optional, None would mean "don't instantiate a default microphone". This would be a bit awkward with respect to other APIs that treat None as "instantiate a default microphone"...
• We could make the classify from file feature a static function of the brick. I remember there are some dependencies on self that are required, probably related to EI. Can we find a workaround for that?

I thought about this solution because it's easy, but I know, maybe it's not the nicest one.

• None means the default microphone, NO_MIC means disabling it. We could define clearer values if you prefer.
• Yes, I tried to remove the dependencies with EI, but it's not easy because we need to move some methods of other subclasses.