re: Dolby Digital/AC3
frequency band:
There is no "16kHz cutoff"
e.g., left channel, Britney Spears 'Toxic', decoded from .ac3:
Dialnorm:
All DD encodes have a dialnorm value in metadata, it is mandatory. It is meant to 'normalize' overall playback level *between different Dolby Digital sources* so that dialogue levels are the same 'comfortable' level for all those sources. Again, dialnorm adjusts overall level, not just the dialogue/center channel. It considers a dialogue level -31dBfs below digital peak (0dBfs, the loudest you can go), as 'ideal' for home playback, and a dialnorm value is programmed in to a DVD as DD stream metadata to 'tell' the decoder how loud its dialogue is. Most commonly for DVDs, that is a dialnorm value of -27, which means that the movie soundtrack has been mixed so that dialogue levels are 4dB (31-27=4) louder than 'ideal', reflecting cinema reference standards but considered louder than 'ideal' for home. Thus the decoder will reduce volume on all channels by 4dB for this program, so everything stays in balance but the dialogue is not 'too loud' for home playback. Meanwhile, a Dolby-encoded TV broadcast stream might have a dialnorm value of -20, so it will be attenuated by -11 dB (31-20=11) by your decoder, to keep the dialogue level at the 'target'. When switching between these two Dolby sources, the perceived dialogue level will be the same (-31 dB fs) , ie.., it won't suddenly sound a lot louder when you go from DVD to TV (-27dbfs -->-20dbfs). That's the point of dialnorm.
tl;dr: it is equivalent to turning the volume knob down on your AVR, nothing more. You are free to adjust the volume back upward by whatever amount suits you if the idea bothers you.
NB1: since DTS encodes do NOT use dialnorm, they typically will NOT be level matched to the equivalent DD encode, upon playback. They may well be louder. (However, to complicate matters, some THX-certified AVRs automatically applied -4dB to DTS sources, in an attempt to even the playing field). This makes it difficult to compare DD to DTS *fairly* by 'trusting your ears'.
NB2: dialnorm of -27 is common for DD movie soundtracks on DVD. For DD content on music discs, e.g., it can be different. A dialnorm of -31 means no level adjustment is done on decode. Typically the AVR receiving a DD bitstream can be made to display the dialnorm value, although my Denon only does it briefly, at the start of a DD program.
NB4: dialnorm is also used for Dolby's Dynamic Range Control (DRC) function, which is an *optional* function. If present, it may be on or off by default in your device, and thus it is worth checking.
frequency band:
There is no "16kHz cutoff"
e.g., left channel, Britney Spears 'Toxic', decoded from .ac3:
Dialnorm:
All DD encodes have a dialnorm value in metadata, it is mandatory. It is meant to 'normalize' overall playback level *between different Dolby Digital sources* so that dialogue levels are the same 'comfortable' level for all those sources. Again, dialnorm adjusts overall level, not just the dialogue/center channel. It considers a dialogue level -31dBfs below digital peak (0dBfs, the loudest you can go), as 'ideal' for home playback, and a dialnorm value is programmed in to a DVD as DD stream metadata to 'tell' the decoder how loud its dialogue is. Most commonly for DVDs, that is a dialnorm value of -27, which means that the movie soundtrack has been mixed so that dialogue levels are 4dB (31-27=4) louder than 'ideal', reflecting cinema reference standards but considered louder than 'ideal' for home. Thus the decoder will reduce volume on all channels by 4dB for this program, so everything stays in balance but the dialogue is not 'too loud' for home playback. Meanwhile, a Dolby-encoded TV broadcast stream might have a dialnorm value of -20, so it will be attenuated by -11 dB (31-20=11) by your decoder, to keep the dialogue level at the 'target'. When switching between these two Dolby sources, the perceived dialogue level will be the same (-31 dB fs) , ie.., it won't suddenly sound a lot louder when you go from DVD to TV (-27dbfs -->-20dbfs). That's the point of dialnorm.
tl;dr: it is equivalent to turning the volume knob down on your AVR, nothing more. You are free to adjust the volume back upward by whatever amount suits you if the idea bothers you.
NB1: since DTS encodes do NOT use dialnorm, they typically will NOT be level matched to the equivalent DD encode, upon playback. They may well be louder. (However, to complicate matters, some THX-certified AVRs automatically applied -4dB to DTS sources, in an attempt to even the playing field). This makes it difficult to compare DD to DTS *fairly* by 'trusting your ears'.
NB2: dialnorm of -27 is common for DD movie soundtracks on DVD. For DD content on music discs, e.g., it can be different. A dialnorm of -31 means no level adjustment is done on decode. Typically the AVR receiving a DD bitstream can be made to display the dialnorm value, although my Denon only does it briefly, at the start of a DD program.
NB4: dialnorm is also used for Dolby's Dynamic Range Control (DRC) function, which is an *optional* function. If present, it may be on or off by default in your device, and thus it is worth checking.
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