Struct AVAudioPCMBuffer

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pub struct AVAudioPCMBuffer { /* private fields */ }

Available on crate feature AVAudioBuffer only.

Expand description

A subclass of AVAudioBuffer for use with PCM audio formats.

AVAudioPCMBuffer provides a number of methods useful for manipulating buffers of audio in PCM format.

Implementations§

Source §

impl AVAudioPCMBuffer

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pub unsafe fn initWithPCMFormat_frameCapacity( this: Allocated<Self>, format: &AVAudioFormat, frame_capacity: AVAudioFrameCount, ) -> Option<Retained<Self>>

Available on crate features AVAudioFormat and AVAudioTypes only.

Initialize a buffer that is to contain PCM audio samples.

Parameter format: The format of the PCM audio to be contained in the buffer.

Parameter frameCapacity: The capacity of the buffer in PCM sample frames.

An exception is raised if the format is not PCM.

Returns nil in the following cases:

if the format has zero bytes per frame (format.streamDescription->mBytesPerFrame == 0)
if the buffer byte capacity (frameCapacity * format.streamDescription->mBytesPerFrame) cannot be represented by an uint32_t

Source

pub unsafe fn initWithPCMFormat_bufferListNoCopy_deallocator( this: Allocated<Self>, format: &AVAudioFormat, buffer_list: NonNull<AudioBufferList>, deallocator: Option<&DynBlock<dyn Fn(NonNull<AudioBufferList>)>>, ) -> Option<Retained<Self>>

Available on crate features AVAudioFormat and block2 and objc2-core-audio-types only.

Initialize a buffer that is to contain PCM audio samples with a given AudioBufferList without copying samples and a custom deallocator block.

Parameter format: The format of the PCM audio to be contained in the buffer.

Parameter bufferList: The buffer list with allocated memory to contain the PCM audio data.

Parameter deallocator: A block to invoke when the resulting AVAudioPCMBuffer object is deallocated.

An exception is raised if the format is not PCM.

Returns nil in the following cases:

if the format has zero bytes per frame (format.streamDescription->mBytesPerFrame == 0)
if supplied buffer has zero number of buffers
if each buffer’s data byte size are not equal or if any of the buffers’ data byte size is zero
if there is a mismatch between the format’s number of buffers and the AudioBufferList’s size (1 if interleaved, mChannelsPerFrame if deinterleaved)
if the AudioBufferList’s pointer to the buffer of audio data is null.

Use the deallocator block to define your own deallocation behavior for the provided AudioBufferList’s underlying memory.

The AudioBufferList passed to the deallocator is identical to the one which was passed to the initializer, in terms of the buffer count, and each buffer’s mData and mDataByteSize members.

§Safety

buffer_list must be a valid pointer.

Source

pub unsafe fn frameCapacity(&self) -> AVAudioFrameCount

Available on crate feature AVAudioTypes only.

The buffer’s capacity, in audio sample frames.

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pub unsafe fn frameLength(&self) -> AVAudioFrameCount

Available on crate feature AVAudioTypes only.

The current number of valid sample frames in the buffer.

You may modify the length of the buffer as part of an operation that modifies its contents. The length must be less than or equal to the frameCapacity. Modifying frameLength will update the mDataByteSize in each of the underlying AudioBufferList’s AudioBuffer’s correspondingly, and vice versa. Note that in the case of deinterleaved formats, mDataByteSize will refers the size of one channel’s worth of audio samples.

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pub unsafe fn setFrameLength(&self, frame_length: AVAudioFrameCount)

Available on crate feature AVAudioTypes only.

Setter for frameLength.

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pub unsafe fn stride(&self) -> NSUInteger

The buffer’s number of interleaved channels.

Useful in conjunction with floatChannelData etc.

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pub unsafe fn floatChannelData(&self) -> *mut NonNull<c_float>

Access the buffer’s float audio samples.

floatChannelData returns pointers to the buffer’s audio samples if the buffer’s format is 32-bit float, or nil if it is another format.

The returned pointer is to format.channelCount pointers to float. Each of these pointers is to “frameLength” valid samples, which are spaced by “stride” samples.

If format.interleaved is false (as with the standard deinterleaved float format), then the pointers will be to separate chunks of memory. “stride” is 1.

If format.interleaved is true, then the pointers will refer into the same chunk of interleaved samples, each offset by 1 frame. “stride” is the number of interleaved channels.

Source

pub unsafe fn int16ChannelData(&self) -> *mut NonNull<i16>

Access the buffer’s int16_t audio samples.

int16ChannelData returns the buffer’s audio samples if the buffer’s format has 2-byte integer samples, or nil if it is another format.

See the discussion of floatChannelData.

Source

pub unsafe fn int32ChannelData(&self) -> *mut NonNull<i32>

Access the buffer’s int32_t audio samples.

int32ChannelData returns the buffer’s audio samples if the buffer’s format has 4-byte integer samples, or nil if it is another format.

See the discussion of floatChannelData.

Source §

impl AVAudioPCMBuffer

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>

Methods from Deref<Target = AVAudioBuffer>§

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pub unsafe fn format(&self) -> Retained<AVAudioFormat>

Available on crate feature AVAudioFormat only.

The format of the audio in the buffer.

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pub unsafe fn audioBufferList(&self) -> NonNull<AudioBufferList>

Available on crate feature objc2-core-audio-types only.

The buffer’s underlying AudioBufferList.

For compatibility with lower-level CoreAudio and AudioToolbox API’s, this method accesses the buffer implementation’s internal AudioBufferList. The buffer list structure must not be modified, though you may modify buffer contents.

The mDataByteSize fields of this AudioBufferList express the buffer’s current frameLength.

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pub unsafe fn mutableAudioBufferList(&self) -> NonNull<AudioBufferList>

Available on crate feature objc2-core-audio-types only.

A mutable version of the buffer’s underlying AudioBufferList.

Some lower-level CoreAudio and AudioToolbox API’s require a mutable AudioBufferList, for example, AudioConverterConvertComplexBuffer.

The mDataByteSize fields of this AudioBufferList express the buffer’s current frameCapacity. If they are altered, you should modify the buffer’s frameLength to match.

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`
    }
}