Start a new topic

MP4 exported file problem

The signal level seems very low in the exported MP4 file.

The .atmos master file monitors at the correct level, both on the internal meters and on an external device.

I've attached an MP4 file that was exported from a master .atmos file that has three tones at -1dB (L), -3dB (R) and -24dB (C). The other channels have nothing. The decoded MP4 version is quite a bit lower than this.

I can send the master file set if required.

Is there some setting that I'm missing?

I'm using the Production Suite on a Nuendo 10 system.

(1.89 MB)

Could you take a loudness analysis of the Master file (Renderer-> Window Menu->Analyse Loudness)? Truth is this is to be expected to some extent. The loudness will dictate the dialnorm level set in the MP4, upon decode this dialnorm level is used to balance average loudness between files so that you’re not reaching for the remote between different movies/shows/tracks. C

Atmos Loudness is:

Short-term -2.6, Momentary -2.6

Integrated -.26, Range 1.8

Integrated (dia) -- , True Peak -1.0

Sorry - 

Integrated = -2.6

Why is there Dialog normalisation applied to the music content when exporting to mp4?

I can also confirm that levels are much lower in mp4 then in the Dolby master files.

1 person likes this

I think the dialnorm value is meant to be determined from either the average dialog level in the centre channel (for a 448kbps export) or from the average multichannel level (for a 768kbps export). There's a good descripton in one of the posts. Why set it for music? - I've no idea.

In any event it doesn't appear to be working correctly. No matter what level is in the master the MP4 export is always much lower.

If it is working correctly it means you can't really use the MP4 export for QA purposes.

I'd like to wake this thread back up.  I'm having the same problem.  My music-only mp4s sound at the proper levels when I play back using Mac Preview, Quicktime player or VLC.  When I move them over to my Plex server, they are considerable lower in level--probably a good 12 dB or so.

To double-check myself I tried it with an Atmos master (music again) from a friend.  I exported mp4s, both in music and film formats. I don't want to mention the friend by name (since that friend probably shouldn't have given me the master), but it's a person who's had success with a lot of Atmos remixes.  This master had an integrated LUFS level of -15.2 and a range of 7.4. True peak was .1. This is very close to the values of my own music master.  It did the same thing--played at proper level locally and played back very quiet on Plex.

I don't think this is Plex, since it plays back music and film videos at reasonably appropriate levels. It's responding to something else in the mix.  Mike Sim mentions dialog normalization and this does sound like a possible culprit.  It seems to me that with a music mix, dialog shouldn't enter in to the equation at all. There does not seem to be a way to turn this off.

I realize I could still be something stupid.  Wouldn't be the first time.  But if you've got hints, I'm all ears.

Please see this webinar episode on the delivery specifications for Dolby Atmos Music and explanation of the usage of dialnorm in the music context:

It is not associated with dialog in any way shape or form. Your finding of -12dB against is inline with expectation but this is really about ensuring your music has access to it's full dynamic range when decoding versus being artificially louder and hitting into decoder limiters etc downstream. 

This webinar session will repeat on May 13th if you'd like to join that session more than happy for live Q&A on the topic. 

1 person likes this

Thanks Ceri!

Don't know how that series of webinars got past me.  I'll catch up now!

Login to post a comment