Enum BufferSize 

pub enum BufferSize {
    Default,
    Fixed(FrameCount),
}

The buffer size requests the callback size for audio streams.

This controls the approximate size of the audio buffer passed to your callback. The actual callback size depends on the host/platform implementation and hardware constraints, and may differ from or vary around the requested size.

Callback Size Expectations

When you specify BufferSize::Fixed(x), you are requesting that callbacks receive approximately x frames of audio data. However, no guarantees can be made about the actual callback size:

• The host may round to hardware-supported values
• Different devices have different constraints
• The callback size may vary between calls (especially on mobile platforms)
• The actual size might be larger or smaller than requested

Latency Considerations

BufferSize::Default uses the host’s default buffer size, which may be surprisingly large, leading to higher latency. If low latency is desired, BufferSize::Fixed should be used with a small value in accordance with the SupportedBufferSize range from SupportedStreamConfig.

Smaller buffer sizes reduce latency but may increase CPU usage and risk audio dropouts if the callback cannot process audio quickly enough.

Example

use cpal::traits::{DeviceTrait, HostTrait};
use cpal::{BufferSize, SupportedBufferSize};

let host = cpal::default_host();
let device = host.default_output_device().unwrap();
let config = device.default_output_config().unwrap();

// Check supported buffer size range
match config.buffer_size() {
    SupportedBufferSize::Range { min, max } => {
        println!("Buffer size range: {} - {}", min, max);
        // Request a small buffer for low latency
        let mut stream_config = config.config();
        stream_config.buffer_size = BufferSize::Fixed(256);
    }
    SupportedBufferSize::Unknown => {
        // Platform doesn't expose buffer size control
        println!("Buffer size cannot be queried on this platform");
    }
}

Variants

Default

Fixed(FrameCount)

Trait Implementations

impl Clone for BufferSize

fn clone(&self) -> BufferSize

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for BufferSize

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for BufferSize

fn eq(&self, other: &BufferSize) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for BufferSize

impl Eq for BufferSize

impl StructuralPartialEq for BufferSize