Improve audio channel mapping

[leo150]

Description & motivation

• Fix audio channel mapping. My previous implementation was creating a channel map of size n, where n is number of input channels. It should use number of output output channels instead.
• Expose channel map for external use
• Add channel map unit tests

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Screenshots:

[leo150]

I added unit tests. makeChannelMap falls back to default value if the provided one is incorrect.

[shogo4405]

I just noticed after the merge that the tests are failing. Is the expected outcome correct?

[leo150]

Hey, thank you for noticing this. The test is incorrect, it should expect [0, -1]. I checked again, it's the only test that is failing. Thanks.

[shogo4405]

Okay, I've fixed the tests. 2e1cb55