Overview: Loudness measurement and control
Loudness measurement and control use different methods to describe or adjust programme level and dynamic behavior.
LUFS measures programme loudness under a defined model. Normalization and ReplayGain use level information for playback decisions, while dynamic-range compression changes the relationship among louder and quieter passages. Dialogue normalization adds another metadata convention. The links below distinguish measurement, metadata and actual signal processing.
LUFS loudness measurement
LUFS expresses standardized programme loudness using frequency weighting, channel energy, measurement windows, and level gating.Loudness normalization
Loudness normalization chooses gain from a programme measurement while accounting for the peak headroom and the intended playback target.ReplayGain
ReplayGain stores recommended track and album playback gains so supporting players can match listening levels without rewriting the audio.Dynamic range compression
Dynamic range compression varies gain according to signal level and time to reduce level contrasts within an audio programme.Dialogue normalization (dialnorm)
Dialnorm metadata describes a Dolby programme's dialogue reference level so the reproduction system can choose a corresponding gain.