# AudioFileReadBytes(_:_:_:_:_:) Reads bytes of audio data from an audio file. ``` func AudioFileReadBytes(_ inAudioFile: AudioFileID, _ inUseCache: Bool, _ inStartingByte: Int64, _ ioNumBytes: UnsafeMutablePointer, _ outBuffer: UnsafeMutableRawPointer) -> OSStatus ``` ## Parameters `inAudioFile` The audio file whose bytes of audio data you want to read. `inUseCache` Set to `true` if you want to cache the data. You should cache reads and writes if you read or write the same portion of a file multiple times. To request that the data not be cached, if possible, set to `false`. You should not cache reads and writes if you read or write data from a file only once. `inStartingByte` The byte offset of the audio data you want to be returned. `ioNumBytes` On input, a pointer to the number of bytes to read. On output, a pointer to the number of bytes actually read. `outBuffer` A pointer to user-allocated memory large enough for the requested bytes. ## Return Value A result code. See Result Codes. ## Discussion In most cases, you should use [`AudioFileReadPackets(_:_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioFileReadPackets(_:_:_:_:_:_:_:)) instead of this function. This function returns `eofErr` when the read operation encounters the end of the file. Note that Audio File Services only reads one 32-bit chunk of a file at a time. --- 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)