Struct AVSampleBufferVideoRenderer

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pub struct AVSampleBufferVideoRenderer { /* private fields */ }

Available on crate feature AVSampleBufferVideoRenderer only.

Expand description

Apple’s documentation

Implementations§

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impl AVSampleBufferVideoRenderer

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pub unsafe fn status(&self) -> AVQueuedSampleBufferRenderingStatus

Available on crate feature AVQueuedSampleBufferRendering only.

The ability of the video renderer to be used for enqueueing sample buffers.

The value of this property is an AVQueuedSampleBufferRenderingStatus that indicates whether the receiver can be used for enqueueing and rendering sample buffers. When the value of this property is AVQueuedSampleBufferRenderingStatusFailed, clients can check the value of the error property to determine the failure. To resume rendering sample buffers using the video renderer after a failure, clients must first reset the status to AVQueuedSampleBufferRenderingStatusUnknown. This can be achieved by invoking -flush on the video renderer. This property is key value observable.

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pub unsafe fn error(&self) -> Option<Retained<NSError>>

If the video renderer’s status is AVQueuedSampleBufferRenderingStatusFailed, this describes the error that caused the failure.

The value of this property is an NSError that describes what caused the video renderer to no longer be able to enqueue sample buffers. If the status is not AVQueuedSampleBufferRenderingStatusFailed, the value of this property is nil.

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pub unsafe fn requiresFlushToResumeDecoding(&self) -> bool

Indicates that the receiver is in a state where it requires a call to -flush to continue decoding frames.

When the application enters a state where use of video decoder resources is not permissible, the value of this property changes to YES along with the video renderer’s status changing to AVQueuedSampleBufferRenderingStatusFailed. To resume rendering sample buffers using the video renderer after this property’s value is YES, clients must first reset the video renderer by calling flush or flushWithRemovalOfDisplayedImage:completionHandler:. Clients can track changes to this property via AVSampleBufferVideoRendererRequiresFlushToResumeDecodingDidChangeNotification. This property is not key value observable.

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pub unsafe fn flushWithRemovalOfDisplayedImage_completionHandler( &self, remove_displayed_image: bool, handler: Option<&DynBlock<dyn Fn()>>, )

Available on crate feature block2 only.

Instructs the video renderer to discard pending enqueued sample buffers and call the provided block when complete.

Parameter removeDisplayedImage: Set YES to remove any currently displayed image, NO to preserve any current image.

Parameter handler: The handler to invoke when flush operation is complete. May be nil.

A flush resets decoder state. The next frame passed to enqueueSampleBuffer: should be an IDR frame (also known as a key frame or sync sample).

§Safety

handler block must be sendable.

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impl AVSampleBufferVideoRenderer

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 AVSampleBufferVideoRenderer

AVSampleBufferVideoRendererPixelBufferOutput.

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pub unsafe fn copyDisplayedPixelBuffer(&self) -> Option<Retained<CVPixelBuffer>>

Available on crate feature objc2-core-video only.

Returns a retained reference to the pixel buffer currently displayed in the AVSampleBufferVideoRenderer’s target. This will return NULL if the displayed pixel buffer is protected, no image is currently being displayed, or if the image is unavailable.

This will return NULL if the rate is non-zero. Clients must release the pixel buffer after use.

Do not write to the returned CVPixelBuffer’s attachments or pixel data.

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impl AVSampleBufferVideoRenderer

AVSampleBufferVideoRendererPowerOptimization.

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pub unsafe fn expectMinimumUpcomingSampleBufferPresentationTime( &self, minimum_upcoming_presentation_time: CMTime, )

Available on crate feature objc2-core-media only.

Promises, for the purpose of enabling power optimizations, that future sample buffers will have PTS values no less than a specified lower-bound PTS.

Only applicable for forward playback. Sending this message and later calling -enqueueSampleBuffer: with a buffer with a lower PTS has the potential to lead to dropping that later buffer. For best results, call -expectMinimumUpcomingSampleBufferPresentationTime: regularly, in between calls to -enqueueSampleBuffer:, to advance the lower-bound PTS. Messaging -flush resets such expectations. (For example, it’s OK to make this expectation, then in response to a seek back, flush and then enqueue buffers with lower PTS values.)

Parameter minimumUpcomingPresentationTime: A lower bound on PTS values for buffers that will be passed to -enqueueSampleBuffer: in the future.

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pub unsafe fn expectMonotonicallyIncreasingUpcomingSampleBufferPresentationTimes( &self, )

Promises, for the purpose of enabling power optimizations, that future sample buffers will have monotonically increasing PTS values.

Only applicable for forward playback. Sending this message and later calling -enqueueSampleBuffer: with a buffer with a lower PTS than any previously enqueued PTS has the potential to lead to dropped buffers. Messaging -flush resets such expectations.

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pub unsafe fn resetUpcomingSampleBufferPresentationTimeExpectations(&self)

Resets previously-promised expectations about upcoming sample buffer PTSs.

This undoes the state set by messaging -expectMinimumUpcomingSampleBufferPresentationTime: or -expectMonotonicallyIncreasingUpcomingSampleBufferPresentationTimes. If you didn’t use either of those, you don’t have to use this.

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pub unsafe fn recommendedPixelBufferAttributes( &self, ) -> Retained<NSDictionary<NSString, AnyObject>>

Recommended pixel buffer attributes for optimal performance when using CMSampleBuffers containing CVPixelBuffers.

The returned dictionary does not contain all of the attributes needed for creating pixel buffers. Use CVPixelBufferCreateResolvedAttributesDictionary() to reconcile these attributes with the pixel buffer creation attributes.

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impl AVSampleBufferVideoRenderer

AVSampleBufferVideoRendererVideoPerformanceMetrics.

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pub unsafe fn loadVideoPerformanceMetricsWithCompletionHandler( &self, completion_handler: &DynBlock<dyn Fn(*mut AVVideoPerformanceMetrics)>, )

Available on crate features AVVideoPerformanceMetrics and block2 only.

Gathers a snapshot of the video performance metrics and calls the completion handler with the results.

Parameter completionHandler: The handler to invoke with the video performance metrics.

If there are no performance metrics available, the completion handler will be called with nil videoPerformanceMetrics.

§Safety

completion_handler block must be sendable.

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`
    }
}