Struct AUAudioUnitBus

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#[repr(C)]
pub struct AUAudioUnitBus { /* private fields */ }

Available on crate feature AUAudioUnit only.

Expand description

An input or output connection point on an audio unit.

Implementations§

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impl AUAudioUnitBus

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pub unsafe fn shouldAllocateBuffer(&self) -> bool

Controls the audio unit’s allocation strategy for a bus.

Hosts can set this flag to communicate whether an audio unit should allocate its own buffer. By default this flag is set to true.

On the output side, shouldAllocateBuffer=false means the AU can assume that it will be called with non-null output buffers. If shouldAllocateBuffer=true (the default), the AU must be prepared to be called with null pointers and replace them with pointers to its internally allocated buffer.

On the input side, shouldAllocateBuffer=false means the AU can pull for input using a buffer list with null buffer pointers, and assume that the pull input block will provide pointers. If shouldAllocateBuffer=true (the default), the AU must pull with non-null pointers while still being prepared for the source to replace them with pointers of its own.

Bridged to the v2 property kAudioUnitProperty_ShouldAllocateBuffer.

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pub unsafe fn setShouldAllocateBuffer(&self, should_allocate_buffer: bool)

Setter for shouldAllocateBuffer.

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pub unsafe fn isEnabled(&self) -> bool

Whether the bus is active.

Hosts must enable input busses before using them. The reason for this is to allow a unit such as a mixer to be prepared to render a large number of inputs, but avoid the work of preparing to pull inputs which are not in use.

Bridged to the v2 properties kAudioUnitProperty_MakeConnection and kAudioUnitProperty_SetRenderCallback.

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pub unsafe fn setEnabled(&self, enabled: bool)

Setter for isEnabled.

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pub unsafe fn name(&self) -> Option<Retained<NSString>>

A name for the bus. Can be set by host.

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pub unsafe fn setName(&self, name: Option<&NSString>)

Setter for name.

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pub unsafe fn index(&self) -> NSUInteger

The index of this bus in the containing array.

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pub unsafe fn busType(&self) -> AUAudioUnitBusType

The AUAudioUnitBusType.

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pub unsafe fn ownerAudioUnit(&self) -> Retained<AUAudioUnit>

The audio unit that owns the bus.

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pub unsafe fn supportedChannelLayoutTags( &self, ) -> Option<Retained<NSArray<NSNumber>>>

This is an array of NSNumbers representing AudioChannelLayoutTag.

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pub unsafe fn contextPresentationLatency(&self) -> NSTimeInterval

Information about latency in the audio unit’s processing context.

This should not be confused with the audio unit’s latency property, where the audio unit describes to the host any processing latency it introduces between its input and its output.

A host may set this property to describe to the audio unit the presentation latency of its input and/or output audio data. Latency is described in seconds. A value of zero means either no latency or an unknown latency.

A host should set this property on each active bus, since, for example, the audio routing path to each of multiple output busses may differ.

For input busses: Describes how long ago the audio arriving on this bus was acquired. For instance, when reading from a file to the first audio unit in a chain, the input presentation latency is zero. For audio input from a device, this initial input latency is the presentation latency of the device itself, i.e. the device’s safety offset and latency.

A second chained audio unit’s input presentation latency will be the input presentation latency of the first unit, plus the processing latency of the first unit.

For output busses: Describes how long it will be before the output audio of an audio unit is presented. For instance, when writing to a file, the output presentation latency of the last audio unit in a chain is zero. When the audio from that audio unit is to be played to a device, then that initial presentation latency will be the presentation latency of the device itself, which is the I/O buffer size, plus the device’s safety offset and latency

A previous chained audio unit’s output presentation latency is the last unit’s presentation latency plus its processing latency.

So, for a given audio unit anywhere within a mixing graph, the input and output presentation latencies describe to that unit how long from the moment of generation it has taken for its input to arrive, and how long it will take for its output to be presented.

Bridged to the v2 property kAudioUnitProperty_PresentationLatency.

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pub unsafe fn setContextPresentationLatency( &self, context_presentation_latency: NSTimeInterval, )

Setter for contextPresentationLatency.

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impl AUAudioUnitBus

Methods declared on superclass NSObject.

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pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

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pub unsafe fn new() -> Retained<Self>

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impl AUAudioUnitBus

AUAudioUnitImplementation. Aspects of AUAudioUnitBus of interest only to the implementation of v3 AUs.

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pub unsafe fn supportedChannelCounts( &self, ) -> Option<Retained<NSArray<NSNumber>>>

Available on crate feature AUAudioUnitImplementation only.

An array of numbers giving the supported numbers of channels for this bus.

If supportedChannelCounts is nil, then any number less than or equal to maximumChannelCount is supported. If setting supportedChannelCounts makes the current format unsupported, then format will be set to nil. The default value is nil.

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pub unsafe fn setSupportedChannelCounts( &self, supported_channel_counts: Option<&NSArray<NSNumber>>, )

Available on crate feature AUAudioUnitImplementation only.

Setter for supportedChannelCounts.

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pub unsafe fn maximumChannelCount(&self) -> AUAudioChannelCount

Available on crate feature AUAudioUnitImplementation only.

The maximum numbers of channels supported for this bus.

If supportedChannelCounts is set, then this value is derived from supportedChannelCounts. If setting maximumChannelCount makes the current format unsupported, then format will be set to nil. The default value is UINT_MAX.

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pub unsafe fn setMaximumChannelCount( &self, maximum_channel_count: AUAudioChannelCount, )

Available on crate feature AUAudioUnitImplementation only.

Setter for maximumChannelCount.

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

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pub unsafe fn get_ivar<T>(&self, name: &str) -> &T
where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

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pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}