Loudness, K-weighted, relative to full scale (LKFS) is a standard
loudness measurement unit used for
audio normalization in
broadcast television systems and other
video
Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...
and
music streaming services.
LKFS is standardized in ITU-R BS.1770. In March 2011, the International Telecommunication Union (
ITU) introduced a loudness gate in the second revision of the recommendation, ITU-R BS.1770-2. In August 2012, the
ITU released the third revision of this recommendation ITU-R BS.1770-3. In October 2015, the ITU released the fourth revision of this recommendation ITU-R BS.1770-4.
Loudness units relative to full scale (LUFS) is a synonym for LKFS that was introduced in
EBU R 128.
The EBU has suggested that the ITU should change the unit to LUFS, as LKFS does not comply with scientific naming conventions and is not in line with the standard set out in ISO 80000-8. Furthermore, they suggest the symbol for ''loudness level, k-weighted'' should be L
k, which would make L
k and LUFS equivalent when LUFS indicates the value of L
k with reference to digital full scale.
LKFS and LUFS are identical in that they are both measured in absolute scale and both equal to one
decibel (dB).
Loudness units (LU) is an additional unit used in EBU R128. It describes L
k without direct absolute reference and therefore describes loudness level differences.
References
{{Reflist
Sound technology