I'll try to explain by example. It's going to be slightly inaccurate, but at least it's also going to be very easy to understand.
First, you have to know what "
normalization" is.
Ever tried listening to a friend's collection of MP3 songs? You listen to the first song and adjust the volume to a level you like. Then the 2nd song's volume is too low, so you increase the player's volume to compensate. But you didn't know that the volume of the 3rd song is too loud, so when that 3rd song plays, you are startled by the overly loud volume.
That MP3 collection needs a program that will set a standard volume level for all songs, so you won't have to reach for the remote to adjust volume for every song. The process of standardizing volume levels for all tracks is called "
Audio Normalization".
The same principle is true for home video. It's natural for some movie soundtracks to be louder than others, depending on the preferences of the engineers who made the DVD/BD masters.
To provide a standardized volume level for home video soundtracks, Dolby came up with "
Dialnorm", which means "
Dialog Normalization".
Dialnorm standardizes audio levels on home video at the production stage by measuring the average dialog level of the input signal, then using a fixed dialog volume level as basis for setting the volume level of the entire soundtrack.
If all audio producers cooperate and use Dolby's approach, users will get the same volume levels across all types of program content, from DVD to BD to all channels of broadcast TV.
As things are now, volume level lang ng TV commercial, hindi pa standardized. Usually nilalakasan ng TV station ang volume ng TV commecial, para happy yung mga sponsors.
... and which audio format uses it?
Only Dolby has it, since Dialnorm is a proprietary meta-data parameter that only works on the Dolby codec system.