Depending on whether you want to burn your audio file to CD, make it available on the Internet, or edit it with an audio editor, the different audio formats are in question. Codecs are responsible for converting to and from the various formats:
PCM (pulse code modulation)
Pulse code modulation is a coding process in which an analog signal can be digitized with almost no loss. Audio material encoded in this way is ideal for further processing because it is not compressed. Data generated with this method is generally saved as wave files with the extension “.wav”.
MP3 (MPEG-1 Audio Layer 3)
The encoding process is actually called MPEG-1 Audio Layer 3 or MPEG-2 Audio Layer 3 and was developed by the Fraunhofer Institute for Integrated Circuits. The name is derived from the associated MP3 file extension of the format. It is one of the first lossy compression processes to rely on psychoacoustic effects on perception to reduce the amount of data. In addition to the original codec from the Fraunhofer Institute, there is also the open source encoder LAME. Files containing data streams encoded in this way usually end in “.mp3”. There are also other container formats that can hold MP3 data streams, such as AVI or MP4.
AAC (advanced audio coding)
AAC is a lossy encoding method that can compress audio data (on a CD) to one-sixteenth of its original size. Compared to MP3, the process can demonstrate higher compression and improved sound quality. Therefore, various online music stores and online radio stations rely on this format. MP4 is designed as a container format to store compressed audio signals. Files containing such an audio track usually end in “.mp4” or “.m4a”.
Vorbis
This open source format is patent-free and therefore can be used by software developers without license fees. The format is also suitable for streaming. Compression is lossy and better than MP3. Although many hardware playback devices now support this format, it is not as widespread as MP3. The data stream is usually embedded in an OGG container. Associated files end in “.ogg” or “.oga”.
WMA (Windows Media Audio)
WMA is an encoding process developed by Microsoft and also offers lossy compression. Many hardware playback devices now support this format, because it is very popular in the music industry due to its built-in copy protection (Digital Rights Management (DRM)). If the file contains only audio data, it ends with “.wma”. ASF is used as the container format.
Why do you need “file formats”?
Digital data used to represent analog video or audio signals can be organized in different formats. The best way to explain this is with a single image – there are multiple options for storing individual pixels in a file. For example, if the image points are stored one after the other from left to right or first from top to bottom in the file it is of course a convention that must be specified. The way a color value is stored must also be clearly defined. These and many other definitions are determined by a specification, which is then implemented in the respective file format. To store the data, a predefined encoding rule is always followed, which is ultimately decisive for the data to be interpreted correctly. You can think of individual formats as different data carriers: CDs, large and small video cassettes, audio tapes, etc. can contain audio data; however, you cannot load a cassette in the CD player. WAV, MP4, WMA or MP3 file formats are equally different.
Many file formats are actually container formats. The term is intended to make it clear that different formats can be used within a convention. For example, an MP4 file can contain different video and audio formats that can also appear in the same file at the same time.
