Had a chat in the morning with the folks on the above subject…
In general …
The DialNorm feature is designed to automatically adjust the volume control so that as to maintain the proper dialogue level while compressing loud effects.
Here is one good article about dialnorm… the encoded information on compression in dolby tracks, why it matters and if you should turn it off if it’s available on your processor / AVR
Here is one article from year 2000 on dial norm
Clear explanation
On the Lyngdorf processor, this feature can be turned off by switching off Dolby’s “Dynamic range compression”
It’s only available on certain processors and AVR
So in short, dialnorm is only applicable with dolby encoded files. It is represented by an integra from -1 to -31 in the dolby metadata. A dialnorm -31 means 0 compression is being applied between the loudest passage and the lowest passage in the encoded soundtrack. So if the file has a dialnorm of -27db, the processor will show -4db dialnorm offset.
There is a difference between dialnorm -27db vs dialnorm offset -27db. Offset here refers to Levels being offset. So a dialnorm -27 means it has a -4db levels dynamic range compression( 31 - 27 = 4db) a dialnorm offset -27db however, means it’s dialnorm -4 ( ie -31 -4 =27db levels offset) with a dialnorm offset of 27db, it simply means the T rex roar is going to sound the same as the man’s voice in the movie. The loudest sound now sounds closer to the softest sound. Not many will enjoy this . Good for watching movies at night so as not to disturb your neighbours, but not good for the guy who wants to enjoy the actual loudness from a T rex or lion roar
It has been reported that in some movies, you have a
Max dialnorm -23db
Average dialnorm -25db
Min dialnorm -27db
Minimum here means the processor will offset 4db A weighted levels
Average means the processor will offset 6db A weighted levels
Max means it offsets 8db A weighted levels, that means it applies a maximum of 8db in compression between dialogue and the loudest sound in the track…
This is often why many people will say… “I prefer the dts soundtrack, it sounds more dynamic!”
Familiar with this sentence ?
So now you know the culprit ? Disable dialnorm and you will restore that dynamic range in the soundtrack
