Delivery & Formatting

We can supply a large number of audio file formats. The most commonly requested types are Wave files (WAV) and MPEG Layer-3 (MP3). There are, however, many other audio file types that we can provide - detailed in the table below. It's worth noting the following:

• The file type is determined by the file extension (what comes after the full stop in the filename). For example, ".wav" and ".mp3".
• The method used to compress and store the audio is called the codec (a contraction of COder and DECoder - describing the two basic functions of telecommunications equipment). This determines how small the file size is, and what it can be played back with.
• Some file types always use a particular codec. For example, MP3 files always use the "MPEG Layer-3" codec. Other files - like WAV files - support selectable codecs. For example, a WAV file can contain uncompressed “PCM” audio, or audio that has been encoded with the "ADPCM", "a-law", “u-law” and other codecs.
• Some file types contain just the audio, whilst others contain additional descriptive information in the file header (e.g. MP3 files can have information about artist, track, album, genre etc).

Audio File Formats

WAV	Standard audio file format, used mainly in Windows PCs. Commonly used for storing uncompressed PCM (Pulse Code Modulation), CD-quality sound files. Files of this type can be large in size - at around 10MB per minute of music. WAV files can contain audio that has been encoded with a variety of codecs to reduce the file size (for example the ADPCM, a-law and u-law codecs). A list of common WAV file codecs can be found below.
IVC	Intervoice’s proprietary file format that contains ADPCM compressed audio.
MP3	The MPEG Layer-3 format is the most popular format for downloading and storing music. By eliminating portions of the audio file that are essentially inaudible, MP3 files are compressed to roughly one tenth the size of an equivalent PCM file, while maintaining good audio quality.
OGG	A free, open source container format supporting a variety of codecs - the most popular of which is the Vorbis audio codec. Vorbis files are often compared to MP3 files in terms of quality, but the OGG format is not as widely supported.
VOX	The VOX format most commonly uses the Dialogic ADPCM (Adaptive Differential Pulse Code Modulation) codec. Similar to other ADPCM formats, it compresses to 4-bits. VOX format files are similar to WAV files, except that the VOX files contain no information about the file itself - so the codec sample rate and number of channels must first be specified in order to play a VOX file.