Struct AVAssetReaderTrackOutput 

pub struct AVAssetReaderTrackOutput { /* private fields */ }

Available on crate feature AVAssetReaderOutput only.

AVAssetReaderTrackOutput is a concrete subclass of AVAssetReaderOutput that defines an interface for reading media data from a single AVAssetTrack of an AVAssetReader’s AVAsset.

Clients can read the media data of an asset track by adding an instance of AVAssetReaderTrackOutput to an AVAssetReader using the -[AVAssetReader addOutput:] method. The track’s media samples can either be read in the format in which they are stored in the asset, or they can be converted to a different format.

See also Apple’s documentation

Implementations

impl AVAssetReaderTrackOutput

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

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

pub unsafe fn assetReaderTrackOutputWithTrack_outputSettings( track: &AVAssetTrack, output_settings: Option<&NSDictionary<NSString, AnyObject>>, ) -> Retained<Self>

Available on crate feature AVAssetTrack only.

Returns an instance of AVAssetReaderTrackOutput for reading from the specified track and supplying media data according to the specified output settings.

Parameter track: The AVAssetTrack from which the resulting AVAssetReaderTrackOutput should read sample buffers.

Parameter outputSettings: An NSDictionary of output settings to be used for sample output. See AVAudioSettings.h for available output settings for audio tracks or AVVideoSettings.h for available output settings for video tracks and also for more information about how to construct an output settings dictionary.

Returns: An instance of AVAssetReaderTrackOutput.

The track must be one of the tracks contained by the target AVAssetReader’s asset.

A value of nil for outputSettings configures the output to vend samples in their original format as stored by the specified track. Initialization will fail if the output settings cannot be used with the specified track.

AVAssetReaderTrackOutput can only produce uncompressed output. For audio output settings, this means that AVFormatIDKey must be kAudioFormatLinearPCM. For video output settings, this means that the dictionary must follow the rules for uncompressed video output, as laid out in AVVideoSettings.h. AVAssetReaderTrackOutput does not support the AVAudioSettings.h key AVSampleRateConverterAudioQualityKey or the following AVVideoSettings.h keys:

AVVideoCleanApertureKey AVVideoPixelAspectRatioKey AVVideoScalingModeKey

When constructing video output settings the choice of pixel format will affect the performance and quality of the decompression. For optimal performance when decompressing video the requested pixel format should be one that the decoder supports natively to avoid unnecessary conversions. Below are some recommendations:

For H.264 use kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange, or kCVPixelFormatType_420YpCbCr8BiPlanarFullRange if the video is known to be full range. For JPEG on iOS, use kCVPixelFormatType_420YpCbCr8BiPlanarFullRange.

For other codecs on OSX, kCVPixelFormatType_422YpCbCr8 is the preferred pixel format for video and is generally the most performant when decoding. If you need to work in the RGB domain then kCVPixelFormatType_32BGRA is recommended.

ProRes encoded media can contain up to 12bits/ch. If your source is ProRes encoded and you wish to preserve more than 8bits/ch during decompression then use one of the following pixel formats: kCVPixelFormatType_4444AYpCbCr16, kCVPixelFormatType_422YpCbCr16, kCVPixelFormatType_422YpCbCr10, or kCVPixelFormatType_64ARGB. AVAssetReader does not support scaling with any of these high bit depth pixel formats. If you use them then do not specify kCVPixelBufferWidthKey or kCVPixelBufferHeightKey in your outputSettings dictionary. If you plan to append these sample buffers to an AVAssetWriterInput then note that only the ProRes encoders support these pixel formats.

ProRes 4444 encoded media can contain a mathematically lossless alpha channel. To preserve the alpha channel during decompression use a pixel format with an alpha component such as kCVPixelFormatType_4444AYpCbCr16 or kCVPixelFormatType_64ARGB. To test whether your source contains an alpha channel check that the track’s format description has kCMFormatDescriptionExtension_Depth and that its value is 32.

Safety

output_settings generic should be of the correct type.

pub unsafe fn initWithTrack_outputSettings( this: Allocated<Self>, track: &AVAssetTrack, output_settings: Option<&NSDictionary<NSString, AnyObject>>, ) -> Retained<Self>

Available on crate feature AVAssetTrack only.

Returns an instance of AVAssetReaderTrackOutput for reading from the specified track and supplying media data according to the specified output settings.

Parameter track: The AVAssetTrack from which the resulting AVAssetReaderTrackOutput should read sample buffers.

Parameter outputSettings: An NSDictionary of output settings to be used for sample output. See AVAudioSettings.h for available output settings for audio tracks or AVVideoSettings.h for available output settings for video tracks and also for more information about how to construct an output settings dictionary.

Returns: An instance of AVAssetReaderTrackOutput.

The track must be one of the tracks contained by the target AVAssetReader’s asset.

A value of nil for outputSettings configures the output to vend samples in their original format as stored by the specified track. Initialization will fail if the output settings cannot be used with the specified track.

AVAssetReaderTrackOutput can only produce uncompressed output. For audio output settings, this means that AVFormatIDKey must be kAudioFormatLinearPCM. For video output settings, this means that the dictionary must follow the rules for uncompressed video output, as laid out in AVVideoSettings.h. AVAssetReaderTrackOutput does not support the AVAudioSettings.h key AVSampleRateConverterAudioQualityKey or the following AVVideoSettings.h keys:

AVVideoCleanApertureKey AVVideoPixelAspectRatioKey AVVideoScalingModeKey

When constructing video output settings the choice of pixel format will affect the performance and quality of the decompression. For optimal performance when decompressing video the requested pixel format should be one that the decoder supports natively to avoid unnecessary conversions. Below are some recommendations:

For H.264 use kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange, or kCVPixelFormatType_420YpCbCr8BiPlanarFullRange if the video is known to be full range. For JPEG on iOS, use kCVPixelFormatType_420YpCbCr8BiPlanarFullRange.

For other codecs on OSX, kCVPixelFormatType_422YpCbCr8 is the preferred pixel format for video and is generally the most performant when decoding. If you need to work in the RGB domain then kCVPixelFormatType_32BGRA is recommended.

ProRes encoded media can contain up to 12bits/ch. If your source is ProRes encoded and you wish to preserve more than 8bits/ch during decompression then use one of the following pixel formats: kCVPixelFormatType_4444AYpCbCr16, kCVPixelFormatType_422YpCbCr16, kCVPixelFormatType_422YpCbCr10, or kCVPixelFormatType_64ARGB. AVAssetReader does not support scaling with any of these high bit depth pixel formats. If you use them then do not specify kCVPixelBufferWidthKey or kCVPixelBufferHeightKey in your outputSettings dictionary. If you plan to append these sample buffers to an AVAssetWriterInput then note that only the ProRes encoders support these pixel formats.

ProRes 4444 encoded media can contain a mathematically lossless alpha channel. To preserve the alpha channel during decompression use a pixel format with an alpha component such as kCVPixelFormatType_4444AYpCbCr16 or kCVPixelFormatType_64ARGB. To test whether your source contains an alpha channel check that the track’s format description has kCMFormatDescriptionExtension_Depth and that its value is 32.

This method throws an exception for any of the following reasons:

• the output settings dictionary contains an unsupported key mentioned above
• the output settings dictionary does not contain any recognized key
• output settings are not compatible with track’s media type
• track output settings would cause the output to yield compressed samples

Safety

output_settings generic should be of the correct type.

pub unsafe fn track(&self) -> Retained<AVAssetTrack>

Available on crate feature AVAssetTrack only.

The track from which the receiver reads sample buffers.

The value of this property is an AVAssetTrack owned by the target AVAssetReader’s asset.

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

The output settings used by the receiver.

The value of this property is an NSDictionary that contains values for keys as specified by either AVAudioSettings.h for audio tracks or AVVideoSettings.h for video tracks. A value of nil indicates that the receiver will vend samples in their original format as stored in the target track.

pub unsafe fn audioTimePitchAlgorithm( &self, ) -> Retained<AVAudioTimePitchAlgorithm>

Available on crate feature AVAudioProcessingSettings only.

Indicates the processing algorithm used to manage audio pitch for scaled audio edits.

Constants for various time pitch algorithms, e.g. AVAudioTimePitchAlgorithmSpectral, are defined in AVAudioProcessingSettings.h. An NSInvalidArgumentException will be raised if this property is set to a value other than the constants defined in that file.

The default value is AVAudioTimePitchAlgorithmSpectral.

This property throws an exception for any of the following reasons:

• a value is set value after reading has started
• a value is set other than AVAudioTimePitchAlgorithmSpectral, AVAudioTimePitchAlgorithmTimeDomain, or AVAudioTimePitchAlgorithmVarispeed.

pub unsafe fn setAudioTimePitchAlgorithm( &self, audio_time_pitch_algorithm: &AVAudioTimePitchAlgorithm, )

Available on crate feature AVAudioProcessingSettings only.

Setter for audioTimePitchAlgorithm.

This is copied when set.

Methods from Deref<Target = AVAssetReaderOutput>

pub unsafe fn mediaType(&self) -> Retained<AVMediaType>

Available on crate feature AVMediaFormat only.

The media type of the samples that can be read from the receiver.

The value of this property is one of the media type strings defined in AVMediaFormat.h.

pub unsafe fn alwaysCopiesSampleData(&self) -> bool

Indicates whether or not the data in buffers gets copied before being vended to the client.

When the value of this property is YES, the AVAssetReaderOutput will always vend a buffer with copied data to the client. Data in such buffers can be freely modified by the client. When the value of this property is NO, the buffers vended to the client may not be copied. Such buffers may still be referenced by other entities. The result of modifying a buffer whose data hasn’t been copied is undefined. Requesting buffers whose data hasn’t been copied when possible can lead to performance improvements.

The default value is YES.

This property throws an exception if a value is set after reading has started (the asset reader has progressed beyond AVAssetReaderStatusUnknown).

pub unsafe fn setAlwaysCopiesSampleData(&self, always_copies_sample_data: bool)

Setter for alwaysCopiesSampleData.

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

Available on crate feature objc2-core-media only.

Copies the next sample buffer for the output synchronously.

Returns: A CMSampleBuffer object referencing the output sample buffer.

The client is responsible for calling CFRelease on the returned CMSampleBuffer object when finished with it. This method will return NULL if there are no more sample buffers available for the receiver within the time range specified by its AVAssetReader’s timeRange property, or if there is an error that prevents the AVAssetReader from reading more media data. When this method returns NULL, clients should check the value of the associated AVAssetReader’s status property to determine why no more samples could be read.

In certain configurations, such as when outputSettings is nil, copyNextSampleBuffer may return marker-only sample buffers as well as sample buffers containing media data. Marker-only sample buffers can be identified by CMSampleBufferGetNumSamples returning 0. Clients who do not need the information attached to marker-only sample buffers may skip them.

This method throws an exception if this output is not added to an instance of AVAssetReader (using -addOutput:) and -startReading is not called on that asset reader.

pub unsafe fn supportsRandomAccess(&self) -> bool

Indicates whether the asset reader output supports reconfiguration of the time ranges to read.

When the value of this property is YES, the time ranges read by the asset reader output can be reconfigured during reading using the -resetForReadingTimeRanges: method. This also prevents the attached AVAssetReader from progressing to AVAssetReaderStatusCompleted until -markConfigurationAsFinal has been invoked.

The default value is NO, which means that the asset reader output may not be reconfigured once reading has begun. When the value of this property is NO, AVAssetReader may be able to read media data more efficiently, particularly when multiple asset reader outputs are attached.

This property throws an exception if a value is set after reading has started (the asset reader has progressed beyond AVAssetReaderStatusUnknown) or after an AVAssetReaderOutput.Provider is attached.

pub unsafe fn setSupportsRandomAccess(&self, supports_random_access: bool)

Setter for supportsRandomAccess.

pub unsafe fn resetForReadingTimeRanges(&self, time_ranges: &NSArray<NSValue>)

Starts reading over with a new set of time ranges.

Parameter timeRanges: An NSArray of NSValue objects, each representing a single CMTimeRange structure

This method may only be used if supportsRandomAccess has been set to YES and may not be called after -markConfigurationAsFinal has been invoked.

This method is often used in conjunction with AVAssetWriter multi-pass (see AVAssetWriterInput category AVAssetWriterInputMultiPass). In this usage, the caller will invoke -copyNextSampleBuffer until that method returns NULL and then ask the AVAssetWriterInput for a set of time ranges from which it thinks media data should be re-encoded. These time ranges are then given to this method to set up the asset reader output for the next pass.

The time ranges set here override the time range set on AVAssetReader.timeRange. Just as with that property, for each time range in the array the intersection of that time range and CMTimeRangeMake(kCMTimeZero, asset.duration) will take effect.

If this method is invoked after the status of the attached AVAssetReader has become AVAssetReaderStatusFailed or AVAssetReaderStatusCancelled, no change in status will occur and the result of the next call to -copyNextSampleBuffer will be NULL.

This method throws an exception if the following conditions are not honored:

• each item in time ranges must be an NSValue
• the start of each time range must be numeric - see CMTIME_IS_NUMERIC
• the duration of each time range must be nonnegative and numeric, or kCMTimePositiveInfinity
• the start of each time range must be greater than or equal to the end of the previous time range
• start times must be strictly increasing
• time ranges must not overlap
• cannot be called before -startReading has been invoked on the attached asset reader
• cannot be called until all samples of media data have been read (i.e. copyNextSampleBuffer returns NULL and the asset reader has not entered a failure state)
• cannot be called without setting “supportsRandomAccess” to YES
• cannot be called after calling -markConfigurationAsFinal

pub unsafe fn markConfigurationAsFinal(&self)

Informs the receiver that no more reconfiguration of time ranges is necessary and allows the attached AVAssetReader to advance to AVAssetReaderStatusCompleted.

When the value of supportsRandomAccess is YES, the attached asset reader will not advance to AVAssetReaderStatusCompleted until this method is called.

When the destination of media data vended by the receiver is an AVAssetWriterInput configured for multi-pass encoding, a convenient time to invoke this method is after the asset writer input indicates that no more passes will be performed.

Once this method has been called, further invocations of -resetForReadingTimeRanges: are disallowed.

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.

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());

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<AVAssetReaderOutput> for AVAssetReaderTrackOutput

fn as_ref(&self) -> &AVAssetReaderOutput

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

impl AsRef<AVAssetReaderTrackOutput> for AVAssetReaderTrackOutput

fn as_ref(&self) -> &Self

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

impl AsRef<AnyObject> for AVAssetReaderTrackOutput

fn as_ref(&self) -> &AnyObject

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

impl AsRef<NSObject> for AVAssetReaderTrackOutput

fn as_ref(&self) -> &NSObject

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

impl Borrow<AVAssetReaderOutput> for AVAssetReaderTrackOutput

fn borrow(&self) -> &AVAssetReaderOutput

Immutably borrows from an owned value.

impl Borrow<AnyObject> for AVAssetReaderTrackOutput

fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value.

impl Borrow<NSObject> for AVAssetReaderTrackOutput

fn borrow(&self) -> &NSObject

Immutably borrows from an owned value.

impl ClassType for AVAssetReaderTrackOutput

const NAME: &'static str = "AVAssetReaderTrackOutput"

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

type Super = AVAssetReaderOutput

The superclass of this class.

type ThreadKind = <<AVAssetReaderTrackOutput 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 AVAssetReaderTrackOutput

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

Formats the value using the given formatter.

impl Deref for AVAssetReaderTrackOutput

type Target = AVAssetReaderOutput

The resulting type after dereferencing.

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

Dereferences the value.

impl Hash for AVAssetReaderTrackOutput

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 AVAssetReaderTrackOutput

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

where Self: Sized,

Increment the reference count of the receiver.

impl NSObjectProtocol for AVAssetReaderTrackOutput

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 AVAssetReaderTrackOutput

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 AVAssetReaderTrackOutput

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

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

impl DowncastTarget for AVAssetReaderTrackOutput

impl Eq for AVAssetReaderTrackOutput