Struct AVCaptureSpatialAudioMetadataSampleGenerator

Source

pub struct AVCaptureSpatialAudioMetadataSampleGenerator { /* private fields */ }

Available on crate feature AVCaptureSpatialAudioMetadataSampleGenerator only.

Expand description

An interface for generating a spatial audio timed metadata sample.

Implementations§

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impl AVCaptureSpatialAudioMetadataSampleGenerator

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pub unsafe fn timedMetadataSampleBufferFormatDescription( &self, ) -> Retained<CMFormatDescription>

Available on crate feature objc2-core-media only.

Returns the format description of the sample buffer returned from the newTimedMetadataSampleBufferAndResetAnalyzer method.

Use this format description when creating your AVAssetWriter track for spatial audio timed metadata.

Source

pub unsafe fn analyzeAudioSample(&self, sbuf: &CMSampleBuffer) -> i32

Available on crate feature objc2-core-media only.

Analyzes the provided audio sample buffer for its contribution to the spatial audio timed metadata value.

Parameter sbuf: a sample buffer containing spatial audio.
Returns: noErr if the sample is successfully analyzed, otherwise a non-zero error code.

You must call this method with each and every spatial audio buffer you provide to AVAssetWriter, so it can be analyzed for the generation of a proper spatial audio timed metadata value.

Source

pub unsafe fn newTimedMetadataSampleBufferAndResetAnalyzer( &self, ) -> Option<Retained<CMSampleBuffer>>

Available on crate feature objc2-core-media only.

Creates a sample buffer containing a spatial audio timed metadata sample computed from all analyzed audio buffers, and resets the analyzer to its initial state.

Returns: a CMSampleBufferRef containing the spatial audio timed metadata sample, or NULL if no value can be computed.

Call this method after you pass the last audio sample buffer of your recording to analyzeAudioSample:. Then pass the returned CMSampleBufferRef directly to your AVAssetWriterInput to add the sample to your recording’s audio timed metadata track. Note that AVAssetWriter expects one and only one spatial audio metadata sample buffer to be present in the timed metadata track.

Note: Calling this method also resets the analyzer, making it ready for another run of audio sample buffers. Thus one generator can be re-used for multiple recordings.

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pub unsafe fn resetAnalyzer(&self)

Calling this method resets the analyzer to its initial state so that a new run of audio sample buffers can be analyzed.

Call this method if you need to abort generating the audio timed metadata buffer for audio already provided to analyzeAudioSample:.

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impl AVCaptureSpatialAudioMetadataSampleGenerator

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>

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());

Source

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.

Source

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`
    }
}