iOS Developer Library


AV Foundation Framework Reference AVAudioMixInputParameters Class Reference

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An AVAudioMixInputParameters object represents the parameters that should be applied to an audio track when it is added to a mix.

You use an instance AVAudioMixInputParameters to apply audio volume ramps for an input to an audio mix. Mix parameters are associated with audio tracks via the trackID property.

Audio volume is currently supported as a time-varying parameter. AVAudioMixInputParameters has a mutable subclass, AVMutableAudioMixInputParameters.

Before the first time at which a volume is set, a volume of 1.0 used; after the last time for which a volume has been set, the last volume is used. Within the time range of a volume ramp, the volume is interpolated between the start volume and end volume of the ramp. For example, setting the volume to 1.0 at time 0 and also setting a volume ramp from a volume of 0.5 to 0.2 with a timeRange of [4.0, 5.0] results in an audio volume parameters that hold the volume constant at 1.0 from 0.0 sec to 4.0 sec, then cause it to jump to 0.5 and descend to 0.2 from 4.0 sec to 9.0 sec, holding constant at 0.2 thereafter.

Given that this is an immutable variant of the object, you should not allocate and initialize a version of this class yourself. Other classes may return instances of this class.

  • Obtains the volume ramp that includes the specified time.



    func getVolumeRampForTime(_ time: CMTime, startVolume startVolume: UnsafeMutablePointer<Float>, endVolume endVolume: UnsafeMutablePointer<Float>, timeRange timeRange: UnsafeMutablePointer<CMTimeRange>) -> Bool


    - (BOOL)getVolumeRampForTime:(CMTime)time startVolume:(float * _Nullable)startVolume endVolume:(float * _Nullable)endVolume timeRange:(CMTimeRange * _Nullable)timeRange



    If a ramp with a time range that contains the specified time has been set, information about the effective ramp for that time is supplied. Otherwise, information about the first ramp that starts after the specified time is supplied.


    A pointer to a float to receive the starting volume value for the volume ramp.

    This value may be NULL.


    A pointer to a float to receive the ending volume value for the volume ramp.

    This value may be NULL.


    A pointer to a CMTimeRange to receive the time range of the volume ramp.

    This value may be NULL.

    Return Value

    YEStrue if the values were retrieved successfully, otherwise NOfalse. Returns NOfalse if time is beyond the duration of the last volume ramp that has been set.


    The process of setting up volume ramps requires the configuration of an instance of AVMutableAudioMixInputParameters.


    Available in iOS 4.0 and later.

  • The audio processing tap associated with the track. (read-only)



    var audioTapProcessor: MTAudioProcessingTap? { get }


    @property(nonatomic, readonly, retain, nullable) MTAudioProcessingTapRef audioTapProcessor


    You can use the audio tap to access the track’s audio data before it is played, read, or exported.

    This property is nil by default.

    The process of setting up a tap requires the configuration of an instance of AVMutableAudioMixInputParameters. If an instance of AVMutableAudioMixInputParameters is present in the inputParameters array of an AVAudioMix, the results of mutating the AVMutableAudioMixInputParameters while the audio mix is in use are undefined


    Available in iOS 6.0 and later.