Struct SNAudioStreamAnalyzer

Source

pub struct SNAudioStreamAnalyzer { /* private fields */ }

Available on crate feature SNAnalyzer only.

Expand description

Analyzes a stream of audio data and provides analysis results to the client

SNAudioStreamAnalyzer should be used to analyze a stream of audio, represented by a sequence of audio buffers over time.

Implementations§

Source §

impl SNAudioStreamAnalyzer

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pub unsafe fn initWithFormat( this: Allocated<Self>, format: &AVAudioFormat, ) -> Retained<Self>

Available on crate feature objc2-avf-audio only.

Creates a new analyzer

Parameter format: The format of the audio stream to be analyzed. Only PCM formats are supported.

Source

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

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pub unsafe fn addRequest_withObserver_error( &self, request: &ProtocolObject<dyn SNRequest>, observer: &ProtocolObject<dyn SNResultsObserving>, ) -> Result<(), Retained<NSError>>

Available on crate features SNRequest and SNResult only.

Adds a new analysis request to the analyzer

Parameters:
request: An audio analysis request to be performed on the audio stream
observer: The object that will receive the analysis results for the supplied request. The observer is weakly retained by the analyzer.
error: On input, a pointer to an error object. If an error occurs, this pointer is set to an actual error object containing the error information. You may specify nil for this parameter if you do not want the error information.
Returns: YES if the request was successfully added, and NO otherwise.

Requests can be added while analysis is in progress. If the analyzer cannot perform the requested analysis, an error will be returned. For example, an error could be returned if the request requires a stream format that doesn’t match the analyzer’s stream format.

Source

pub unsafe fn removeRequest(&self, request: &ProtocolObject<dyn SNRequest>)

Available on crate feature SNRequest only.

Removes an existing analysis request from the analyzer

Parameter request: An audio analysis request to be removed Requests can be removed while analysis is in progress. Once the removeRequest method returns, the previously registered observer will not receive any more callbacks.

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pub unsafe fn removeAllRequests(&self)

Removes all requests from the analyzer

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pub unsafe fn analyzeAudioBuffer_atAudioFramePosition( &self, audio_buffer: &AVAudioBuffer, audio_frame_position: AVAudioFramePosition, )

Available on crate feature objc2-avf-audio only.

Provides the next buffer for analysis

Parameters:
audioBuffer: The buffer containing the audio to be processed
audioFramePosition: The frame position of the data in the buffer

The framePosition should be a monotonically increasing sample timestamp. If the sample timeline is detected to be non-continuous, the analyzer’s internal state may reset to account for the jump. Some types of audio analysis are performed at a fixed block size, which may differ from the buffer sizes provided for analysis. For this reason, an invocation of analyzeAudioBuffer may cause an analysis request observer to be called zero times, one time, or many times, depending on the relationship between the input buffer size, current analyzer state, and native analysis block size. Any errors produced during analysis will be provided through the request observers. This method may block as a means of indicating backpressure to the caller. These methods are not safe to call from a realtime audio context but may be called from lower priority threads (i.e. AVAudioEngine tap callback or AudioQueue callback).

Source

pub unsafe fn completeAnalysis(&self)

Indicates that the audio stream has ended, and no more audio buffers will be analyzed

After this method has been called, it is invalid to provide any more audio data for analysis, and any provided buffers will be ignored. This method is useful for types of analysis that may have final results to provide upon the completion of the stream.

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impl SNAudioStreamAnalyzer

Methods declared on superclass NSObject.

Source

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

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>§

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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());

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`
    }
}