[Feature proposal] Get channel names of a device for certain platforms

[nico-franco-gomez]

Some hosts such as CoreAudio or ASIO support having string names for each input/output channel of a device (besides their index). So far, I have not seen this functionality implemented in CPAL, but it would be very useful for a project where users can select input or output channels based on their names rather than the index. Is this a feature that would be worth implementing? Is there maybe a reason why this hasn't been done yet?

[nico-franco-gomez]

Hello! I went ahead and wrote some code for a project where the channel names are provided for the aforementioned hosts. Would it be of interest here, even though it may not be available to all platforms? If so, I could start a PR with this functionality since more people might find it useful

[roderickvd]

We've got device_by_id now with stable device IDs, I'd not be against a PR that would introduce something like device_by_name. Or are you saying it's on Stream rather than on Device?

[nico-franco-gomez]

Well, a device_by_name would certainly be nice. But what I was talking about here was regarding names of the channels within a Device. There is, for instance, in ASIO: ASIOGetChannelInfo(), you would get a struct and there you have a char[32] which contains some name/description for the channel.

If you find this interesting, I'll try to start a PR with my implementation. As stated before, I've only done it for ASIO and CoreAudio. I'm actually not certain that the other hosts even support having channel names...

[roderickvd]

Could you sketch out the API with a small example?

[nico-franco-gomez]

I imagine something like this

pub trait DeviceTrait {
    fn get_channel_name(&self, channel_index: u16, input_channel: bool) -> Result<String, ChannelNameError>;
    // Alternatively
    fn get_input_channel_name(&self, channel_index: u16) -> Result<String, ChannelNameError>;
    fn get_output_channel_name(&self, channel_index: u16) -> Result<String, ChannelNameError>;

    // Optional: Getting all at the same time
    fn get_channel_names(&self, input_channels: bool) -> Result<Vec<String>, ChannelNameError>;
}

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub enum ChannelNameError {
    NotImplemented,
    ChannelIndexOutOfRange,
    BackendSpecific { err: BackendSpecificError },
}

// Usage might look like
fn main() {
    assert!("Left" == device.get_channel_name(0, false).unwrap());
    assert!("Right" == device.get_channel_name(1, false).unwrap());

    assert!("Microphone 1" == device.get_channel_name(0, true).unwrap());
}

Keeping the low-level approach of the crate, I wouldn't think of getting all the names at once as the go-to option.