# init(buffer:bufferStartTime:) Creates an audio input object for audio that may be discontiguous with previous input. ``` init(buffer: AVAudioPCMBuffer, bufferStartTime: CMTime?) ``` ## Parameters `buffer` An audio buffer. `bufferStartTime` The time-code of the start of the audio buffer. If `nil`, this audio buffer is assumed to start immediately after the previous buffer (or at time-code zero if there is no previous buffer). The `CMTime` can have a different timescale than the sample rate of the audio data. ## Discussion The audio buffer must not overlap or precede other audio input, as determined by the `bufferStartTime` value. > Important: If the buffer is converted from other differently-formatted audio, ensure that the buffer’s start time is accurate. > > Some conversion algorithms can use a “priming” method that may shift some audio to a later converted buffer. This shift will misalign the original and converted audio buffers; the original buffer’s start time would not be usable as the `bufferStartTime` value for the converted buffer. > Tip: Convert an `AVAudioTime` instance to a `CMTime` instance with this code. > > ```swift > CMTime(value: avAudioTime.sampleTime, timescale: CMTimeScale(avAudioTime.sampleRate)) > ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)