Struct VNVideoProcessor

Source

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

Available on crate feature VNVideoProcessor only.

Expand description

A controller object that is used to perform one or more requests on a video stream.

VNVideoProcessor handles the video decoding and buffer management, feeding the buffers to the associated requests at the best desired frame rate.

Implementations§

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impl VNVideoProcessor

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

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pub unsafe fn initWithURL( this: Allocated<Self>, video_url: &NSURL, ) -> Retained<Self>

Creates a VNVideoProcessor to be used for performing requests against a video asset specified by it’s URL.

Parameter videoURL: A URL pointing at a video asset on which the requests will be performed. The video format has to be supported by AVFoundation.

Source

pub unsafe fn addRequest_processingOptions_error( &self, request: &VNRequest, processing_options: &VNVideoProcessorRequestProcessingOptions, ) -> Result<(), Retained<NSError>>

Available on crate feature VNRequest only.

Add a VNRequest with the specified processing options to be performed on the video.

This method can be called either before calling -analyzeTimeRange:error: or from within one of the already associated request’s completion handlers.

Parameter request: The VNRequest to be added to the processing pipeline. If added from within a completionHandler, it will be processed on the same frame that is currently being processed.

Parameter processingOptions: The options applied to the request’s processing of the video.

Parameter error: Returns an error that happened during scheduling of the requests. Check individual requests results and errors for their respective success and failures. This parameter is optional.

Returns: Returns true if the request added to the processing pipeline.

Note: The VNRequest must have completion handler set otherwise no results can be returned.

Source

pub unsafe fn addRequest_withProcessingOptions_error( &self, request: &VNRequest, processing_options: &NSDictionary<VNVideoProcessingOption, AnyObject>, ) -> Result<(), Retained<NSError>>

👎Deprecated

Available on crate features VNRequest and VNTypes only.

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pub unsafe fn removeRequest_error( &self, request: &VNRequest, ) -> Result<(), Retained<NSError>>

Available on crate feature VNRequest only.

Remove a VNRequest from the video processor, which means it won’t be performed anymore.

This method can be called either before calling -analyzeTimeRange:error: or from within one of the already associated request’s completion handlers.

Parameter request: The VNRequest to be removed from the processing pipeline.

Parameter error: Returns an error that happened during processing of the request, such as if the request was not found in the processing queue. This parameter is optional.

Returns: Returns true if the request was found and removed from the processing pipeline.

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pub unsafe fn analyzeTimeRange_error( &self, time_range: CMTimeRange, ) -> Result<(), Retained<NSError>>

Available on crate feature objc2-core-media only.

Processes the video over the specified time range.

This call is synchronous and only returns after the video is processed through its duration or an error prevented the processing.

Parameter timeRange: Start and duration of the timerange within video to process. If the duration is longer than the video (e.g., kCMTimeIndefinite) the processing stops at the end of the video.

Parameter error: Returns an error that happened during the starting of the processing queue (for instance if the time range is not valid for the video asset). This parameter is optional.

Returns: Returns true if all requests were scheduled and performed. Check individual requests results and errors for their respective success and failures.

Note: The intersection of the CMTimeRangeMake(start, duration) and CMTimeRangeMake(kCMTimeZero, asset.duration) will determine the timerange of the video to process

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pub unsafe fn analyzeWithTimeRange_error( &self, time_range: CMTimeRange, ) -> Result<(), Retained<NSError>>

👎Deprecated

Available on crate feature objc2-core-media only.

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pub unsafe fn cancel(&self)

Cancel the processing of the video. This can return before the last request has completed.

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impl VNVideoProcessor

Methods declared on superclass NSObject.

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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());

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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.

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`
    }
}