You can also test whether it provides a particular media type or supports a given capture session preset using hasMediaType: and supportsAVCaptureSessionPreset: respectively. You can ask a device about its different characteristics. You add an input device to a capture session using a capture input (see Use Capture Inputs to Add a Capture Device to a Session). You should register to receive AVCaptureDeviceWasConnectedNotification and AVCaptureDeviceWasDisconnectedNotification notifications to be alerted when the list of available devices changes. Current input devices may become unavailable (if they’re used by another application), and new input devices may become available, (if they’re relinquished by another application). The list of available devices may change, though. And, if necessary, you can find out what features an iPhone, iPad, or iPod offers (see Device Capture Settings). You can find out which capture devices are currently available using the AVCaptureDevice class methods devices and devicesWithMediaType. There is one object for each input device, for example, two video inputs-one for the front-facing the camera, one for the back-facing camera-and one audio input for the microphone. An AVCaptureDevice Object Represents an Input DeviceĪn AVCaptureDevice object abstracts a physical capture device that provides input data (such as audio or video) to an AVCaptureSession object. Additionally, both the running and interrupted properties are key-value observing compliant and the notifications are posted on the main thread. You can also interrogate the session’s running property to find out if it is running, and its interrupted property to find out if it is interrupted. You can register to receive an AVCaptureSessionRuntimeErrorNotification if a runtime error occurs. You can also use a connection to monitor the average and peak power levels in an audio channel.Ī capture session posts notifications that you can observe to be notified, for example, when it starts or stops running, or when it is interrupted. You can use a capture connection to enable or disable the flow of data from a given input or to a given output. Figure 4-2 AVCaptureConnection represents a connection between an input and output
A connection between a capture input and a capture output is represented by an AVCaptureConnection object. When you add an input or an output to a session, the session forms connections between all the compatible capture inputs’ ports and capture outputs, as shown in Figure 4-2. Capture outputs (instances of AVCaptureOutput) can accept data from one or more sources (for example, an AVCaptureMovieFileOutput object accepts both video and audio data). Capture inputs (instances of AVCaptureInput) have one or more input ports (instances of AVCaptureInputPort). For some operations, however, (if you want to monitor the power levels in an audio channel, for example) you need to consider how the various ports of an input device are represented and how those ports are connected to the output.Ī connection between a capture input and a capture output in a capture session is represented by an AVCaptureConnection object. You can configure multiple inputs and outputs, coordinated by a single session, as shown in Figure 4-1 Figure 4-1 A single session can configure multiple inputs and outputsįor many applications, this is as much detail as you need. To show the user a preview of what the camera is recording, you can use an instance of AVCaptureVideoPreviewLayer (a subclass of CALayer).
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Minimally you need:Īn instance of AVCaptureDevice to represent the input device, such as a camera or microphoneĪn instance of a concrete subclass of AVCaptureInput to configure the ports from the input deviceĪn instance of a concrete subclass of AVCaptureOutput to manage the output to a movie file or still imageĪn instance of AVCaptureSession to coordinate the data flow from the input to the output To manage the capture from a device such as a camera or microphone, you assemble objects to represent inputs and outputs, and use an instance of AVCaptureSession to coordinate the data flow between them. Next Previous Still and Video Media Capture
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