# Audio File Formats

Audio files are used to store digital audio. Audio files usually contain information about the included audio waveform's characteristics and how it is stored. An audio file format usually specifies the sample rate, bit-depth, and type of compression used as well as other information that indicates how long the waveform is, how much data must be read per second of play-time, etc. Most of an audio file's content is used to describe the individual audio samples that are played sequentially to reconstruct the waveform. The waveform data can be compressed in different ways to help reduce the large size of a stream of audio samples. Every minute of uncompressed CD quality (44.1 kHz, 16-bit, stereo) audio requires about 10 MB of storage space. AIFF files The AIIF file format is the most commonly supported audio file format on the Mac platform. It is capable of storing waveform data in many different formats. The most common type of AIFF files contains uncompressed (raw PCM) waveform data. Even though compressed audio continues to become more popular because of limited storage space, AIFF files still tend to contain uncompressed waveform data while other file formats (such as MP3 and AAC/M4A) are used for compressed data. MP3 files MP3 is a file format that stores music files on a computer in such a way that the file size is relatively small, but the song sounds near perfect. You can identify MP3 files by the .mp3 ending. The size of an MP3 file is typically 1 MB per minute of music. MP3 files are actually MPEG-1 (MPEG version 1) or MPEG-2 (MPEG version 2) files. Both types can be encoded as Layer I, Layer II or Layer III. Amazing Slow Downer can playback any of these types. AAC/MP4 - QuickTime files AAC/MP4 files is a new file format that competes with Windows Media Audio files (WMA) and is now standard with Mac's and iPod's. Files purchased from the Apple iTunes store (.m4p files) are supported by Amazing Slow Downer but since they are protected by a DRM (Digital Rights Management) license you are not allowed to re-save the files - playback only. Those files usually have .m4p as their file name extension. You may however burn the purchased songs to a CD - this way you can circumvent the DRM protection and also re-save the files using Amazing Slow Downer. Musepack files Musepack is an audio compression format with a strong emphasis on high quality. It's not lossless, but it is designed for transparency, so that you won't be able to hear differences between the original wave file and the much smaller MPC file. It is based on the MPEG-1 Layer-2 / MP2 algorithms, but since 1997 it has rapidly developed and vastly improved and is now at an advanced stage in which it contains heavily optimized and patentless code. WMA - Windows Media Audio files Microsoft’s respond to MP3, the Windows Media Audio standard is firmly integrated in Microsoft’s Windows Media Player (WMP). Microsoft promises almost CD-quality with just a third of the source-file’s size. Above all WMA offers the advantage that copyright-protected songs cannot be published any further (DRM - Digital Rights Management). Note: To be able to playback Windows Media Audio files, you need to install the Flip4Mac QuickTime component: http://www.flip4mac.com/ Ogg Vorbis files Ogg Vorbis is a fully open, non-proprietary, patent-and-royalty-free, general-purpose compressed audio format for high quality (44.1 - 48.0 kHz, 16+ bit, polyphonic) audio and music. The Ogg Vorbis music encoding format is contemporary to MPEG-4's AAC and TwinVQ, the next generation beyond MPEG audio layer 3. Unlike the MPEG sponsored formats (and other proprietary formats such as RealAudio G2 and Windows' WMA), the Vorbis CODEC specification belongs to the public domain. All the technical details are published and documented, and any software entity may make full use of the format without royalty or patent concerns. FLAC (Free Lossless Audio Codec) files FLAC stands for Free Lossless Audio Codec. Grossly oversimplified, FLAC is similar to MP3, but lossless, meaning that audio is compressed in FLAC without any loss in quality. This is similar to how Zip works, except with FLAC you will get much better compression because it is designed specifically for audio, and you can play back compressed FLAC files in your favorite player (or your car or home stereo) just like you would an MP3 file. Note: To be able to playback Ogg Vorbis and FLAC files you need to install a free framework availble here: http://www.ronimusic.com/miscdownload.htm