TVOAudioFormat

Objective-C

@interface TVOAudioFormat : NSObject

Swift

class TVOAudioFormat : NSObject

TVOAudioFormat describes audio that is captured or rendered via a TVOAudioDevice. The class also offers convenience methods to help interoperate with CoreAudio and size your audio buffers appropriately.

  • @brief The number of channels in the audio stream.

    @discussion Valid values for this property are either 1 or 2. Only mono and stereo LPCM audio are supported.

    Declaration

    Objective-C

    @property (nonatomic, readonly) size_t numberOfChannels;

    Swift

    var numberOfChannels: Int { get }

  • @brief The sample rate of the audio stream in units of frequency (Hz), i.e. the number of audio samples per second.

    @discussion Valid values for this property are 8000, 16000, 24000, 32000, 44100 and 48000 Hz.

    Declaration

    Objective-C

    @property (nonatomic, readonly) uint32_t sampleRate;

    Swift

    var sampleRate: UInt32 { get }

  • @brief The maximum number of frames contained in a single audio buffer.

    @discussion The underlying media engine operates on 20 millisecond slices of LPCM audio. Ideally, your audio device should capture and render in exactly 10 millisecond buffers. However, in many cases this is not possible on iOS. If you’re using AudioUnits to produce or consume audio you should use AVAudioSession.preferredIOBufferDuration to request appropriately sized buffers.

    Declaration

    Objective-C

    @property (nonatomic, readonly) size_t framesPerBuffer;

    Swift

    var framesPerBuffer: Int { get }

  • Unavailable

    TVOAudioFormat can not be created with init

    @brief Developers shouldn’t use init to create TVOAudioFormat.

    @discussion Use initWithChannels:sampleRate:framesPerBuffer: instead.

    Declaration

    Objective-C

    - (null_unspecified instancetype)init;

  • @brief Initializes an instance of TVOAudioFormat.

    @discussion TVOAudioFormat describes signed 16-bit LPCM audio. This is the working format used to interoperate between TVOAudioDevice and the underlying media engine. Please note that the media engine may be forced to perform a format conversion depending on the codecs used for sending and receiving audio. For example, ISAC accepts mono 32 kHz audio while OPUS accepts mono or stereo at 48 kHz.

    See

    TVOAudioCodec

    Declaration

    Objective-C

    - (nullable instancetype)initWithChannels:(size_t)channels
                               sampleRate:(uint32_t)sampleRate
                          framesPerBuffer:(size_t)framesPerBuffer;

    Swift

    init?(channels: Int, sampleRate: UInt32, framesPerBuffer: Int)

    Parameters

    channels

    The number of channels in the audio stream.
    sampleRate

    The sample rate of the audio stream.
    framesPerBuffer

    The maximum number of frames contained in a single audio stream buffer.

    Return Value

    An instance of TVOAudioFormat, which is immutable once created. Returns nil if one or more parameters passed to the initializer are not supported by the SDK.

  • @brief Computes the required buffer size for a given audio format.

    @discussion This helper method can be used to size audio buffers appropriately.

    Declaration

    Objective-C

    - (size_t)bufferSize;

    Swift

    func bufferSize() -> Int

    Return Value

    The required buffer size, in bytes, to work with a given TVOAudioFormat.

  • @brief Generates an audio stream description which can be used with CoreAudio.

    @discussion AudioStreamBasicDescription can be used to describe many different constant bitrate audio formats. Since TVOAudioFormat defines only signed 16-bit LPCM audio there is a well known transformation between the two.

    Declaration

    Objective-C

    - (AudioStreamBasicDescription)streamDescription;

    Swift

    func streamDescription() -> AudioStreamBasicDescription

    Return Value

    An AudioStreamBasicDescription which reflects the properties of the TVOAudioFormat being queried.