The iPhone's built-in Voice Memos app is an ideal way to take meeting minutes or capture ideas on the move. It records sound in the MPEG-4 Audio multimedia file format, which is used to store compressed audio. Compression allows recordings to take up less storage space than they would if they were left as raw sound files. However, although M4A allows for efficient file storage, it is not compatible with all media players.
Voice Memos is a voice-recording app that uses the iPhone's built-in microphone to capture sound -- press a button to start the recording, then press the button again to stop. Once the recording is stopped, it is automatically saved to the app's memory. The Voice Memos menu screen allows you to share your recordings over email or as a multimedia message. Although the recordings do not show up in the iPhone's iTunes menu, they are still transferred when the phone is synced to a computer that has iTunes running.
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M4A is part of the MPEG-4 family of file formats. MPEG-4 is used to store media such as audio and video, and is the successor to the MPEG-3 format, better known as MP3. The extension used by MPEG-4 files usually differs depending on the content of that file. For example, .m4v is the video equivalent of .m4a, while .mp4 can be used for various types of multimedia files. In addition, MPEG-4 files can be copy-protected using the FairPlay system. This changes the extension used to .m4p.
M4A files use one of two codecs to compress audio. A codec is an algorithm that reduces the size of a file by removing its redundant parts. When the file is selected, the codec decodes it, allowing it to be played back. The two codecs used by M4A files are known as Advanced Audio Coding and Apple Lossless Audio Codec. By default, iPhone voice memos are encoded using AAC, which produces high levels of compression but can cause a slight loss in audio quality.
M4A files are widely supported by Mac OS X audio programs, as Apple also uses the format for downloads from the iTunes store. Roxio Toast 11 and RealNetworks RealPlayer are among the native OS X programs offering M4A support. The format is also well-supported on Windows machines, although not all versions of Windows Media Player can run it by default. Windows Media Player 11 requires the K-Lite Codec Pack in order to play M4A files, although Media Player 12 supports the format natively.