Trait cpal::traits::HostTrait

source ·

pub trait HostTrait {
    type Devices: Iterator<Item = Self::Device>;
    type Device: DeviceTrait;

    // Required methods
    fn is_available() -> bool;
    fn devices(&self) -> Result<Self::Devices, DevicesError>;
    fn default_input_device(&self) -> Option<Self::Device>;
    fn default_output_device(&self) -> Option<Self::Device>;

    // Provided methods
    fn input_devices(&self) -> Result<InputDevices<Self::Devices>, DevicesError> { ... }
    fn output_devices(
        &self
    ) -> Result<OutputDevices<Self::Devices>, DevicesError> { ... }
}

Expand description

A Host provides access to the available audio devices on the system.

Each platform may have a number of available hosts depending on the system, each with their own pros and cons.

For example, WASAPI is the standard audio host API that ships with the Windows operating system. However, due to historical limitations with respect to performance and flexibility, Steinberg created the ASIO API providing better audio device support for pro audio and low-latency applications. As a result, it is common for some devices and device capabilities to only be available via ASIO, while others are only available via WASAPI.

Another great example is the Linux platform. While the ALSA host API is the lowest-level API available to almost all distributions of Linux, its flexibility is limited as it requires that each process have exclusive access to the devices with which they establish streams. PulseAudio is another popular host API that aims to solve this issue by providing user-space mixing, however it has its own limitations w.r.t. low-latency and high-performance audio applications. JACK is yet another host API that is more suitable to pro-audio applications, however it is less readily available by default in many Linux distributions and is known to be tricky to set up.