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"Convert Audio Files To/From All Audio Formats with Switch"
NCH’s Switch Audio File Converter is, while not as free, as open-source and as community-driven as VirtualDub, enables the conversion and the encoding of audio files, and supports a variety of common (and some even uncommon) audio file formats, both for input and output. Like most NCH multimedia software, the Switch Audio File Converter is available on both PC (running on Windows XP and up) and Mac (for Mac OS X 10.3 and later). As a sound file converter, this application essentially transforms or converts one audio file written or encoded in a format, and re-encodes it into another format chosen by the user with zero loss of quality. It is also smaller than most professional tools in this regard as well, and it shows it by having faster performance and smaller memory footprint and impact than its far bloated competitors.
The Switch Audio File Converter also allows batch conversion from and to audio file formats, the importing and conversion of entire playlists, import video files and extract the audio from these files and save it as an MP3 (currently supported videos are AVI, MPEG, and WMV). It can also compress audio files so it can fit well on your mobile device (and use them as a ringtone).