# Audio File Stream Services Parse streamed audio files as the data arrives on the user’s computer. ## Discussion Audio File Stream Services provides the interface for parsing streamed audio files—in which only a limited window of data is available at a time. Audio file streams, by nature, are not random access. When you request data from a stream, earlier data might no longer be accessible and later data might not yet be available. In addition, the data you obtain (and then provide to a parser) might include partial packets. To parse streamed audio data, then, a parser must remember data from partially satisfied requests, and must be able to wait for the remainder of that data. In other words, a parser must be able to suspend parsing as needed and then resume where it left off. To use a parser, you pass data from a streamed audio file, as you acquire it, to the parser. When the parser has a complete packet of audio data or a complete property, it invokes a callback function. Your callbacks then process the parsed data—such as by playing it or writing it to disk. Here, in outline form, is a typical usage pattern for an audio file stream parser: 1. Create a new audio file stream parser by calling the [`AudioFileStreamOpen(_:_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamOpen(_:_:_:_:_:)) function. Pass pointers to your callback functions for audio data and metadata ([`AudioFileStream_PacketsProc`](/documentation/AudioToolbox/AudioFileStream_PacketsProc) and [`AudioFileStream_PropertyListenerProc`](/documentation/AudioToolbox/AudioFileStream_PropertyListenerProc)). The [`AudioFileStreamOpen(_:_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamOpen(_:_:_:_:_:)) function gives you a reference to the new parser. 2. Acquire some streamed data. Call the [`AudioFileStreamParseBytes(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamParseBytes(_:_:_:_:)) function when you have data to pass to the parser. Send the data to the parser sequentially and, if possible, without gaps. 3. When the parser acquires a usable buffer of audio data, it invokes your audio data callback. Your callback can then play the data, write it to a file, or otherwise process it. 4. When the parser acquires metadata, it invokes your property callback—which in turn can obtain the property value by calling the [`AudioFileStreamGetPropertyInfo(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamGetPropertyInfo(_:_:_:_:)) and [`AudioFileStreamGetProperty(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamGetProperty(_:_:_:_:)) functions. 5. When finished parsing a stream, call the [`AudioFileStreamClose(_:)`](/documentation/AudioToolbox/AudioFileStreamClose(_:)) function to close and deallocate the parser. Audio File Stream Services supports the following audio data types: - AIFF - AIFC - WAVE - CAF - NeXT - ADTS - MPEG Audio Layer 3 - AAC ## Topics ### Opening Audio File Streams [`AudioFileStreamOpen(_:_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamOpen(_:_:_:_:_:)) Creates and opens a new audio file stream parser. ### Supplying Data to the Parser [`AudioFileStreamParseBytes(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamParseBytes(_:_:_:_:)) Passes audio file stream data to the parser. ### Seeking Packets in the Data Stream [`AudioFileStreamSeek(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamSeek(_:_:_:_:)) Provides a byte offset for a specified packet in the data stream. ### Working with Data Stream Property Information [`AudioFileStreamGetPropertyInfo(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamGetPropertyInfo(_:_:_:_:)) Retrieves information about a property value. [`AudioFileStreamGetProperty(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamGetProperty(_:_:_:_:)) Retrieves the value of the specified property. [`AudioFileStreamSetProperty(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamSetProperty(_:_:_:_:)) Sets the value of the specified property. ### Closing an Audio File Stream [`AudioFileStreamClose(_:)`](/documentation/AudioToolbox/AudioFileStreamClose(_:)) Closes and deallocates the specified audio file stream parser. ### Callbacks [`AudioFileStream_PropertyListenerProc`](/documentation/AudioToolbox/AudioFileStream_PropertyListenerProc) Invoked by an audio file stream parser when it finds a property value in the audio file stream. [`AudioFileStream_PacketsProc`](/documentation/AudioToolbox/AudioFileStream_PacketsProc) Invoked by an audio file stream parser when it finds audio data in the audio file stream. ### Data Types [`AudioFileStreamPropertyID`](/documentation/AudioToolbox/AudioFileStreamPropertyID) Uniquely identifies an audio file stream property. [`AudioFileStreamID`](/documentation/AudioToolbox/AudioFileStreamID) Defines an opaque data type that represents an audio file stream parser. ### Enumerations [Audio File Stream Errors](/documentation/AudioToolbox/1391572-audio-file-stream-errors) [Audio File Types](/documentation/AudioToolbox/1576497-audio-file-types) ### Constants [Audio File Stream Flags](/documentation/AudioToolbox/audio-file-stream-flags) Flags set by the property listener callback and the [`AudioFileStreamParseBytes(_:_:_:_:)`](/documentation/AudioToolbox/AudioFileStreamParseBytes(_:_:_:_:)) function. [Audio File Stream Properties](/documentation/AudioToolbox/1391506-audio-file-stream-properties) Audio file stream properties contain information that you can use to help interpret the audio data in a stream. ### Result Codes This table lists the result codes defined for Audio File Stream Services. [Audio File Errors](/documentation/AudioToolbox/1576500-audio-file-errors) [`kAudioFileStreamError_UnsupportedFileType`](/documentation/AudioToolbox/kAudioFileStreamError_UnsupportedFileType) The specified file type is not supported. [`kAudioFileStreamError_UnsupportedDataFormat`](/documentation/AudioToolbox/kAudioFileStreamError_UnsupportedDataFormat) The data format is not supported by the specified file type. [`kAudioFileStreamError_UnsupportedProperty`](/documentation/AudioToolbox/kAudioFileStreamError_UnsupportedProperty) The property is not supported. [`kAudioFileStreamError_BadPropertySize`](/documentation/AudioToolbox/kAudioFileStreamError_BadPropertySize) The size of the buffer you provided for property data was not correct. [`kAudioFileStreamError_NotOptimized`](/documentation/AudioToolbox/kAudioFileStreamError_NotOptimized) It is not possible to produce output packets because the streamed audio file’s packet table or other defining information is not present or appears after the audio data. [`kAudioFileStreamError_InvalidPacketOffset`](/documentation/AudioToolbox/kAudioFileStreamError_InvalidPacketOffset) A packet offset was less than `0`, or past the end of the file, or a corrupt packet size was read when building the packet table. [`kAudioFileStreamError_InvalidFile`](/documentation/AudioToolbox/kAudioFileStreamError_InvalidFile) The file is malformed, not a valid instance of an audio file of its type, or not recognized as an audio file. [`kAudioFileStreamError_ValueUnknown`](/documentation/AudioToolbox/kAudioFileStreamError_ValueUnknown) The property value is not present in this file before the audio data. [`kAudioFileStreamError_DataUnavailable`](/documentation/AudioToolbox/kAudioFileStreamError_DataUnavailable) The amount of data provided to the parser was insufficient to produce any result. [`kAudioFileStreamError_IllegalOperation`](/documentation/AudioToolbox/kAudioFileStreamError_IllegalOperation) An illegal operation was attempted. [`kAudioFileStreamError_UnspecifiedError`](/documentation/AudioToolbox/kAudioFileStreamError_UnspecifiedError) An unspecified error has occurred. [`kAudioFileStreamError_DiscontinuityCantRecover`](/documentation/AudioToolbox/kAudioFileStreamError_DiscontinuityCantRecover) A discontinuity has occurred in the audio data, and Audio File Stream Services cannot recover. --- Copyright © 2026 Apple Inc. 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