Struct AVAssetReader

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

Available on crate feature AVAssetReader only.

AVAssetReader provides services for obtaining media data from an asset.

Instances of AVAssetReader read media data from an instance of AVAsset, whether the asset is file-based or represents an assembly of media data from multiple sources, as is the case with AVComposition.

Clients of AVAssetReader can read data from specific tracks of an asset and in specific formats by adding concrete instances of AVAssetReaderOutput to an AVAssetReader instance.

AVAssetReaderTrackOutput, a concrete subclass of AVAssetReaderOutput, can either read the track’s media samples in the format in which they are stored by the asset or convert the media samples to a different format.

AVAssetReaderAudioMixOutput mixes multiple audio tracks of the asset after reading them, while AVAssetReaderVideoCompositionOutput composites multiple video tracks after reading them.

See also Apple’s documentation

Implementations

impl AVAssetReader

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

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

pub unsafe fn assetReaderWithAsset_error( asset: &AVAsset, ) -> Result<Retained<Self>, Retained<NSError>>

Available on crate feature AVAsset only.

Returns an instance of AVAssetReader for reading media data from the specified asset.

Parameter asset: The asset from which media data is to be read.

Parameter outError: On return, if initialization of the AVAssetReader fails, points to an NSError describing the nature of the failure.

Returns: An instance of AVAssetReader.

If the specified asset belongs to a mutable subclass of AVAsset, AVMutableComposition or AVMutableMovie, the results of any asset reading operation are undefined if you mutate the asset after invoking -startReading.

pub unsafe fn initWithAsset_error( this: Allocated<Self>, asset: &AVAsset, ) -> Result<Retained<Self>, Retained<NSError>>

Available on crate feature AVAsset only.

Creates an instance of AVAssetReader for reading media data from the specified asset.

Parameter asset: The asset from which media data is to be read.

Parameter outError: On return, if initialization of the AVAssetReader fails, points to an NSError describing the nature of the failure.

Returns: An instance of AVAssetReader.

If the specified asset belongs to a mutable subclass of AVAsset, AVMutableComposition or AVMutableMovie, the results of any asset reading operation are undefined if you mutate the asset after invoking -startReading.

pub unsafe fn asset(&self) -> Retained<AVAsset>

Available on crate feature AVAsset only.

The asset from which the receiver’s outputs read sample buffers.

The value of this property is an AVAsset. Concrete instances of AVAssetReader that are created with specific AVAssetTrack instances must obtain those tracks from the asset returned by this property.

pub unsafe fn status(&self) -> AVAssetReaderStatus

The status of reading sample buffers from the receiver’s asset.

The value of this property is an AVAssetReaderStatus that indicates whether reading is in progress, has completed successfully, has been canceled, or has failed. Clients of AVAssetReaderOutput objects should check the value of this property after -[AVAssetReaderOutput copyNextSampleBuffer] returns NULL to determine why no more samples could be read. This property is thread safe.

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

If the receiver’s status is AVAssetReaderStatusFailed, this describes the error that caused the failure.

The value of this property is an NSError that describes what caused the receiver to no longer be able to read its asset. If the receiver’s status is not AVAssetReaderStatusFailed, the value of this property is nil. This property is thread safe.

pub unsafe fn timeRange(&self) -> CMTimeRange

Available on crate feature objc2-core-media only.

Specifies a range of time that may limit the temporal portion of the receiver’s asset from which media data will be read.

The intersection of the value of timeRange and CMTimeRangeMake(kCMTimeZero, asset.duration) will determine the time range of the asset from which media data will be read. The default value of timeRange is CMTimeRangeMake(kCMTimeZero, kCMTimePositiveInfinity).

This property throws an exception if a value is set after reading has started.

pub unsafe fn setTimeRange(&self, time_range: CMTimeRange)

Available on crate feature objc2-core-media only.

Setter for timeRange.

pub unsafe fn outputs(&self) -> Retained<NSArray<AVAssetReaderOutput>>

Available on crate feature AVAssetReaderOutput only.

The outputs from which clients of receiver can read media data.

The value of this property is an NSArray containing concrete instances of AVAssetReaderOutput. Outputs can be added to the receiver using the addOutput: method.

pub unsafe fn canAddOutput(&self, output: &AVAssetReaderOutput) -> bool

Available on crate feature AVAssetReaderOutput only.

Tests whether an output can be added to the receiver.

Parameter output: The AVAssetReaderOutput object to be tested.

Returns: A BOOL indicating whether the output can be added to the receiver.

An output that reads from a track of an asset other than the asset used to initialize the receiver cannot be added.

pub unsafe fn addOutput(&self, output: &AVAssetReaderOutput)

Available on crate feature AVAssetReaderOutput only.

Adds an output to the receiver.

Parameter output: The AVAssetReaderOutput object to be added.

Outputs are created with a reference to one or more AVAssetTrack objects. These tracks must be owned by the asset returned by the receiver’s asset property.

This method throws an exception if the output has already been added to an AVAssetReader or if reading has started (status has progressed beyond AVAssetReaderStatusUnknown).

pub unsafe fn startReading(&self) -> bool

Prepares the receiver for reading sample buffers from the asset.

Returns: A BOOL indicating whether reading could be started.

This method validates the entire collection of settings for outputs for tracks, for audio mixing, and for video composition and initiates reading from the receiver’s asset.

If this method returns NO, clients can determine the nature of the failure by checking the value of the status and error properties.

This method throws an exception if reading has already started (status has progressed beyond AVAssetReaderStatusUnknown).

pub unsafe fn cancelReading(&self)

Cancels any background work and prevents the receiver’s outputs from reading more samples.

Clients that want to stop reading samples from the receiver before reaching the end of its time range should call this method to stop any background read ahead operations that the may have been in progress.

This method should not be called concurrently with any calls to -[AVAssetReaderOutput copyNextSampleBuffer].

Methods from Deref<Target = NSObject>

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

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>

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

Dynamically find the class of this object.

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());

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.

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`
    }
}

Trait Implementations

impl AsRef<AVAssetReader> for AVAssetReader

fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<AnyObject> for AVAssetReader

fn as_ref(&self) -> &AnyObject

Converts this type into a shared reference of the (usually inferred) input type.

impl AsRef<NSObject> for AVAssetReader

fn as_ref(&self) -> &NSObject

Converts this type into a shared reference of the (usually inferred) input type.

impl Borrow<AnyObject> for AVAssetReader

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<NSObject> for AVAssetReader

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl ClassType for AVAssetReader

const NAME: &'static str = "AVAssetReader"

The name of the Objective-C class that this type represents.

type Super = NSObject

The superclass of this class.

type ThreadKind = <<AVAssetReader as ClassType>::Super as ClassType>::ThreadKind

Whether the type can be used from any thread, or from only the main thread.

fn class() -> &'static AnyClass

Get a reference to the Objective-C class that this type represents.

fn as_super(&self) -> &Self::Super

Get an immutable reference to the superclass.

impl Debug for AVAssetReader

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

Formats the value using the given formatter.

impl Deref for AVAssetReader

type Target = NSObject

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Hash for AVAssetReader

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Message for AVAssetReader

fn retain(&self) -> Retained<Self>

where Self: Sized,

Increment the reference count of the receiver.

impl NSObjectProtocol for AVAssetReader

fn isEqual(&self, other: Option<&AnyObject>) -> bool

where Self: Sized + Message,

Check whether the object is equal to an arbitrary other object.

fn hash(&self) -> usize

where Self: Sized + Message,

An integer that can be used as a table address in a hash table structure.

fn isKindOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of the class, or one of its subclasses.

fn is_kind_of<T>(&self) -> bool

where T: ClassType, Self: Sized + Message,

👎Deprecated: use isKindOfClass directly, or cast your objects with AnyObject::downcast_ref

Check if the object is an instance of the class type, or one of its subclasses.

fn isMemberOfClass(&self, cls: &AnyClass) -> bool

where Self: Sized + Message,

Check if the object is an instance of a specific class, without checking subclasses.

fn respondsToSelector(&self, aSelector: Sel) -> bool

where Self: Sized + Message,

Check whether the object implements or inherits a method with the given selector.

fn conformsToProtocol(&self, aProtocol: &AnyProtocol) -> bool

where Self: Sized + Message,

Check whether the object conforms to a given protocol.

fn description(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object.

fn debugDescription(&self) -> Retained<NSObject>

where Self: Sized + Message,

A textual representation of the object to use when debugging.

fn isProxy(&self) -> bool

where Self: Sized + Message,

Check whether the receiver is a subclass of the NSProxy root class instead of the usual NSObject.

fn retainCount(&self) -> usize

where Self: Sized + Message,

The reference count of the object.

impl PartialEq for AVAssetReader

fn eq(&self, other: &Self) -> 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 RefEncode for AVAssetReader

const ENCODING_REF: Encoding = <NSObject as ::objc2::RefEncode>::ENCODING_REF

The Objective-C type-encoding for a reference of this type.

impl DowncastTarget for AVAssetReader

impl Eq for AVAssetReader