Dialnorm

The purpose of dialnorm (dialog normalization) is to maintain a consistent dialog level for the listener. Dolby Labratories requires dialnorm implementation in every Dolby Digital encoder and decoder.

The dialnorm metadata parameter is set in the encoder, and ranges from -31 to -1. If dialnorm is increased from -31 to -1, the decoder reduces the audio level by an equal number of decibels.

Dolby suggests setting this parameter equal to the encoder digital input average A-weighted dialog level unique to each show. They also recognize that it may be simpler to fix dialnorm at a setting appropriate to archives, and adjust the audio mix of new productions to match. This eliminates the need to implement a complex metadata system. The ETVCookbook test kitchen measures dialnorm of -25 for typical PBS network shows (with a -20 dBFS reference level.)See: Understanding Dialnorm

Dolby Labs