Editing Windows Media Audio (section)

==Container format==
{{Main|Advanced Systems Format}}

A WMA file is in most circumstances contained in the [[Advanced Systems Format]] (ASF), a [[Proprietary software|proprietary]] Microsoft [[Container format (digital)|container format]] for [[digital audio]] or [[digital video]].<ref>{{cite web |url=http://support.microsoft.com/kb/284094 |title=The Difference Between ASF and WMV/WMA Files |publisher=Microsoft |access-date=2007-08-16 |url-status=live |archive-url=https://web.archive.org/web/20070819113435/http://support.microsoft.com/kb/284094 |archive-date=2007-08-19 }}</ref> The ASF container format specifies how [[Metadata (computing)|metadata]] about the file is to be encoded, similar to the [[ID3]] tags used by MP3 files. Metadata may include song name, track number, artist name, and also [[audio normalization]] values. This container can optionally support [[digital rights management]] (DRM) using a combination of [[elliptic curve cryptography]] key exchange, [[Data Encryption Standard|DES]] block cipher, a custom block cipher, [[RC4 cipher|RC4]] stream cipher and the [[SHA-1]] hashing function. See [[Windows Media DRM]] for further information.

Since 2008 Microsoft has also been using WMA Professional in its Protected Interoperable File Format (PIFF) based on the [[ISO base media file format|ISO Base Media File Format]] and most commonly used for Smooth Streaming, a form of adaptive bitrate streaming over HTTP. Related industry standards such as DECE [[UltraViolet (system)|UltraViolet]] and [[MPEG-DASH]] have not standardized WMA as a supported audio codec, deciding in favor of the more industry-prevalent MPEG and Dolby audio codecs.