MPEG Audio Info (MPEG Audio Frame Header) is about the structure of the MPEG audio frame header including the XING and VBRI headers. The aim is to estimate the duration of the MPEG audio file as exact and fast as possible. The article does not include any hints on how to decode/encode the actual audio data. MPEG audio files exist in different layers. The most common is the MPEG 1 Layer III (also known as MP3), as it has the most sophisticated compression technology.

An MPEG audio file consists out of frames. Each frame contains a header at its beginning followed by the audio data. This audio data always contains a fixed number of samples. There currently exists three layers of MPEG audio, which differ in how the audio data is encoded in the frame, although they all have the same header format. The frame itself consists of slots. In Layer I, a slot is always 4 byte long, in all other the layers a slot is 1 byte long.

Additional to the layers there are also three versions of MPEG audio, which differ in the sampling rate they can handle. MPEG 1 (ISO/IEC 13818-3) and MPEG 2 (ISO/IEC 11172-3) are ISO standards. MPEG 2.5 is an unofficial extension of MPEG 2 to support even lower sampling rates. MPEG 2/2.5 is also known under the abbreviation LSF, which stands for Lower Sampling Frequencies. Each version can handle the three layers. If you want to know more about the technical details of an MPEG audio file please have a look at the specifications.

A file can be encoded either with a constant bitrate (CBR) or with a variable bitrate (VBR), which means that each frame can have a different bitrate. Therefore, the quality of those files is often higher than files encoded in constant a bitrate mode, because they can use higher bitrates where the music needs it.

The license of this software is Freeware, you can free download and free use this audio utility software.