Delivery Spec Question

[Rick Sanchez]

I'm new to LKFS measurement and have a Dolby Media Meter 2 set up on a 5.1 AUX that gets in input from the same buss that is feeding the 5.1 mix stem.

I just got a delivery spec that calls for -24 LKFS (+/- 2dB) global loudness (on a 5.1 mix).

It also calls for Peak limiting of 5.1 channel soundtracks of -2dBFS.

For the 2 channel, it also calls Peak Limiting of 2 channel only soundtracks: Limit to -2dBFS.

I assume global loudness means feeding all 5.1 channels to the Dolby Media Meter and reading Infinite All and not Infinite Dialog. With the target set for -24 and a tolerance of +2 and -2.

The peak limiting is a bit confusing. When I get an LKFS reading -24, it sounds fairly close to where I would normally mix. Dialog now hits between -2 and +2 on the Dorrough. I brick wall the composite mix at -10dBFS. So what does the -2dBFS Peak Limiting pertain to?

[Postman]

So what does the -2dBFS Peak Limiting pertain to?

It means you don't have to brickwall the living daylights out of your mix if you don't want to.

[shockwave2501]

set ur limiter to -2 dbfs and your peaks will be fine. Most of the time when they are asking for LKFS or dialogue norms I use infinite dialogue to measure my mix. hope that sheds some light for you.

[EarHole]

Now, that doesn't mean you can slam it with the L1 @-2 dbs on the stereo mix.
It's supposed to mirror the level of the 5.1 mix.

[Audio_Vision]

You are correct regarding the global loudness measurement, dialogue intelligence should be OFF. LKFS is optimized for measuring all full bandwidth channels. This also gave us more metering options with ITU 1770(T.C. Electronic, RTW, etc), as dialogue intelligence is Dolby proprietary.

[Pete Gates]

Not being impolite Keith but that documentation is mostly irrelevant to the previous posters as I think they're all US based. One thing, it does seem almost contrary that they've gone for -23 rather than -24 : shades of -18/-20. It was a great chance to simplify what has become a complete minefield over the last few years.

Pete

[hummerZ]

I'm very rarely seeing dialogue-based LKFS specs. Everything seems to be moving towards "global loudness," as your spec says. So, Infinite All on the DMM (although I like to keep an eye on Short Term All as well)

[Rick Sanchez]

Thanks all...Looks like we're all going through the same learning curve, so it's nice to get some second opinions.

I spoke with the guy and Dolby and he also said that the -2dBFS peak limiter setting was a bit curious if you are mixing to -24 LKFS Infinite All with a +/- 2dB range, as he said you probably would not go anywhere NEAR -2dBFS. Probably just a safety valve.

Really just ignoring the meter and mixing by ear in my smallish room at 76dB monitor level, I was very close to in speck. Had to make a couple of minor adjustments, but sample peaks were still hitting around -8 on the Dolby meter. and -10 on a Peak meter and a Dorrough.

[Postman]

Thank you kdarbyshirebryant (keith?) for that link!!! I had not seen the ebu document and personally found it interesting. What is most interesting is the ebu document specifies a gated measurement, basically anything below -8lu does not count toward the LUFS/LKFS total. ITU and the ATSC recommendations suggest no gating. Also, ebu are in favor of including the LFE channel (with 10db boost) in the measurement. ATSC (and ITU) do not include the LFE channel. Finally, they seem to prefer loudness normalization from the source...that's you and I... over loudness normalization through metadata.

Very interesting. The variety of expectations on audio vendors is a P.F. (abbreviated US expression), as usual. -23lufs, -24lkfs, -27lkfs, -10dbfs, -8dbfs, -4dbfs, -2dbfs. Mix and match.

[Tstein]

Can anyone explain the logic behind the EBU's gated measurement?