Struct AVAssetWriterInputPixelBufferAdaptor

Source

pub struct AVAssetWriterInputPixelBufferAdaptor { /* private fields */ }

Available on crate feature AVAssetWriterInput only.

Expand description

Apple’s documentation

Implementations§

Source §

pub unsafe fn assetWriterInputPixelBufferAdaptorWithAssetWriterInput_sourcePixelBufferAttributes( input: &AVAssetWriterInput, source_pixel_buffer_attributes: Option<&NSDictionary<NSString, AnyObject>>, ) -> Retained<Self>

Creates a new pixel buffer adaptor to receive pixel buffers for writing to the output file.

In order to take advantage of the improved efficiency of appending buffers created from the adaptor’s pixel buffer pool, clients should specify pixel buffer attributes that most closely accommodate the source format of the video frames being appended.

Pixel buffer attributes keys for the pixel buffer pool are defined in <CoreVideo /CVPixelBuffer.h>. To specify the pixel format type, the pixelBufferAttributes dictionary should contain a value for kCVPixelBufferPixelFormatTypeKey. For example, use [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] for 8-bit-per-channel BGRA. See the discussion under appendPixelBuffer:withPresentationTime: for advice on choosing a pixel format.

Clients that do not need a pixel buffer pool for allocating buffers should set sourcePixelBufferAttributes to nil.

This method throws an exception if the input is already attached to another asset writer input pixel buffer adaptor or if the input has already started writing (the asset writer has progressed beyond AVAssetWriterStatusUnknown).

Parameter input: An instance of AVAssetWriterInput to which the receiver should append pixel buffers. Currently, only asset writer inputs that accept media data of type AVMediaTypeVideo can be used to initialize a pixel buffer adaptor.
Parameter sourcePixelBufferAttributes: Specifies the attributes of pixel buffers that will be vended by the input’s CVPixelBufferPool.
Returns: An instance of AVAssetWriterInputPixelBufferAdaptor.

§Safety

source_pixel_buffer_attributes generic should be of the correct type.

Source

pub unsafe fn initWithAssetWriterInput_sourcePixelBufferAttributes( this: Allocated<Self>, input: &AVAssetWriterInput, source_pixel_buffer_attributes: Option<&NSDictionary<NSString, AnyObject>>, ) -> Retained<Self>

Creates a new pixel buffer adaptor to receive pixel buffers for writing to the output file.

In order to take advantage of the improved efficiency of appending buffers created from the adaptor’s pixel buffer pool, clients should specify pixel buffer attributes that most closely accommodate the source format of the video frames being appended.

Pixel buffer attributes keys for the pixel buffer pool are defined in <CoreVideo /CVPixelBuffer.h>. To specify the pixel format type, the pixelBufferAttributes dictionary should contain a value for kCVPixelBufferPixelFormatTypeKey. For example, use [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] for 8-bit-per-channel BGRA. See the discussion under appendPixelBuffer:withPresentationTime: for advice on choosing a pixel format.

Clients that do not need a pixel buffer pool for allocating buffers should set sourcePixelBufferAttributes to nil.

This method throws an exception if the input is already attached to another asset writer input pixel buffer adaptor or if the input has already started writing (the asset writer has progressed beyond AVAssetWriterStatusUnknown).

Parameter input: An instance of AVAssetWriterInput to which the receiver should append pixel buffers. Currently, only asset writer inputs that accept media data of type AVMediaTypeVideo can be used to initialize a pixel buffer adaptor.
Parameter sourcePixelBufferAttributes: Specifies the attributes of pixel buffers that will be vended by the input’s CVPixelBufferPool.
Returns: An instance of AVAssetWriterInputPixelBufferAdaptor.

§Safety

source_pixel_buffer_attributes generic should be of the correct type.

Source

pub unsafe fn assetWriterInput(&self) -> Retained<AVAssetWriterInput>

The asset writer input to which the receiver should append pixel buffers.

Source

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

The pixel buffer attributes of pixel buffers that will be vended by the receiver’s CVPixelBufferPool.

The value of this property is a dictionary containing pixel buffer attributes keys defined in <CoreVideo /CVPixelBuffer.h>.

Source

pub unsafe fn pixelBufferPool(&self) -> Option<Retained<CVPixelBufferPool>>

Available on crate feature objc2-core-video only.

A pixel buffer pool that will vend and efficiently recycle CVPixelBuffer objects that can be appended to the receiver.

For maximum efficiency, clients should create CVPixelBuffer objects for appendPixelBuffer:withPresentationTime: by using this pool with the CVPixelBufferPoolCreatePixelBuffer() function.

The value of this property will be NULL before -[AVAssetWriter startWriting] is called on the associated AVAssetWriter object.

This property is key value observable.

This property throws an exception if a pixel buffer pool cannot be created with this asset writer input pixel buffer adaptor’s source pixel buffer attributes (must specify width, height, and either pixel format or pixel format description).

Source

pub unsafe fn appendPixelBuffer_withPresentationTime( &self, pixel_buffer: &CVPixelBuffer, presentation_time: CMTime, ) -> bool

Available on crate features objc2-core-media and objc2-core-video only.

Appends a pixel buffer to the receiver.

The receiver will retain the CVPixelBuffer until it is done with it, and then release it. Do not modify a CVPixelBuffer or its contents after you have passed it to this method.

For optimal performance the format of the pixel buffer should match one of the native formats supported by the selected video encoder. Below are some recommendations:

The H.264 and HEVC encoders natively support kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange and kCVPixelFormatType_420YpCbCr8BiPlanarFullRange, which should be used with 8-bit 4:2:0 video and full range input respectively; other related pixel formats in CoreVideo/CVPixelBuffer.h are ideal for 4:2:2 and 4:4:4 (and for HEVC, 10-bit). The JPEG encoder on iOS and Apple Silicon macOS natively supports kCVPixelFormatType_422YpCbCr8FullRange. If you need to work in the RGB domain then kCVPixelFormatType_32BGRA is recommended on iOS and macOS.

Pixel buffers not in a natively supported format will be converted internally prior to encoding when possible. Pixel format conversions within the same range (video or full) are generally faster than conversions between different ranges.

The ProRes encoders can preserve high bit depth sources, supporting up to 12bits/ch. ProRes 4444 can contain a mathematically lossless alpha channel and it doesn’t do any chroma subsampling. This makes ProRes 4444 ideal for quality critical applications. If you are working with 8bit sources ProRes is also a good format to use due to its high image quality. Use either of the recommended pixel formats above. Note that RGB pixel formats by definition have 4:4:4 chroma sampling.

If you are working with high bit depth sources the following yuv pixel formats are recommended when encoding to ProRes: kCVPixelFormatType_4444AYpCbCr16, kCVPixelFormatType_422YpCbCr16, and kCVPixelFormatType_422YpCbCr10. When working in the RGB domain kCVPixelFormatType_64ARGB is recommended. Scaling and color matching are not currently supported when using AVAssetWriter with any of these high bit depth pixel formats. Please make sure that your track’s output settings dictionary specifies the same width and height as the buffers you will be appending. Do not include AVVideoScalingModeKey or AVVideoColorPropertiesKey.

Before calling this method, you must ensure that the input that underlies the receiver is attached to an AVAssetWriter via a prior call to -addInput: and that -startWriting has been called on the asset writer. It is an error to invoke this method before starting a session (via -[AVAssetWriter startSessionAtSourceTime:]) or after ending a session (via -[AVAssetWriter endSessionAtSourceTime:]).

This method throws an exception if the presentation time is is non-numeric (see CMTIME_IS_NUMERIC) or if “readyForMoreMediaData” is NO.

Parameter pixelBuffer: The CVPixelBuffer to be appended.
Parameter presentationTime: The presentation time for the pixel buffer to be appended. This time will be considered relative to the time passed to -[AVAssetWriter startSessionAtSourceTime:] to determine the timing of the frame in the output file.
Returns: A BOOL value indicating success of appending the pixel buffer. If a result of NO is returned, clients can check the value of AVAssetWriter.status to determine whether the writing operation completed, failed, or was cancelled. If the status is AVAssetWriterStatusFailed, AVAsset.error will contain an instance of NSError that describes the failure.

Methods from Deref<Target = NSObject>§

Source

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

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

Source

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`
    }
}