What is mastering in the context of the Dolby Atmos for Music format?

The intention is to answer all aspects of this question whether you are an artist, manager, A&R or label representative or a mix and/or mastering engineer respectively.

Tools

While the technology is still developing and iterating, at the time of writing, there are four main tools to best enable mastering your Dolby Atmos project:

• Digital Audio Workstation [DAW] – including ProTools, Pyramix, Nuendo, Cubase, StudioOne & Logic
• Dolby Atmos Renderer [DAR] (Integrated or External)
• Dolby Atmos Album Assembler [DAAA]
• Dolby Atmos Conversion Tool [DACT]

Note: There are other tools such as the Fiedler Audio range, but because we have not validated them we have not included the use of them in this documentation. No tool is prohibited as long as the output files pass QC.

The Mastering Process

This document acknowledges the mastering engineer could be:

1. A Dolby Atmos Mix Engineer
2. A Dolby Atmos Mastering Engineer independent of the Mix Engineer
3. A Studio offering both Dolby Atmos Mix and Mastering services

In respect of (3), it is at the discretion of the engineers how the work would be assigned between them, prior to commencement of the project.

We also acknowledge that the engineer could be the original stereo mix and/or mastering engineer respectively.

The predominant workflow at the time of writing is:

Stereo Mixing > Stereo Mastering > Dolby Atmos Mixing + Mastering

As mastering workflows/tools are still being developed and, in most cases, creative intention is being provided by the stereo master, it has become common practice for the Dolby Atmos mix engineer to both mix and master.

As the technology and tools develop, and as creators become more experienced with the format, we will start to see a shift in the adoption of new approaches and workflows (e.g. Dolby Atmos mix created independently from the stereo mix and/or the stereo mix being derived from the Dolby Atmos mix). As such, both the Dolby Atmos mixing and mastering processes may or may not adopt a different creative approach to the stereo versions.

Responsibilities of the Mastering Engineer

In order to build an understanding of the Dolby Atmos mastering engineer’s remit, we have discussed this topic with a range of mix and mastering engineers globally. Each project, as with stereo projects, should be treated on a case-by-case basis, but all points below should be considered and acknowledged by the mastering engineer to enable them in delivering a final product that passes our internal QC review. We would generally not expect to see a mastering engineer conducting work outside of the list below, without prior discussion with the original creative team.

Global Gain, EQ & Dynamic Processing

As per standard requirements of a stereo mastering engineer, confirm to what degree this is required.

Gapless Transitions

This is a continued complexity of the Dolby Atmos workflow and differs dramatically from stereo, especially if one has not been made aware prior to commencement and/or tracks were mixed by different engineers. Importing ADMs into the same session in a DAW when potentially dealing with different engineers mixes or workflows, can be difficult. Currently the only way to do this is working with ADMs via a DAW. It cannot be completed in the DAAA, although it can be used to either reference your exported tracks and/or split after the crossfade is completed in a DAW.

Binaural Metadata

Review for appropriate binaural metadata and, if required engage with the mix engineer or label, prior to adjusting parameters and ensure settings are persevered upon completion. Changes can be made in various ways:

• Load the ADM into the Renderer software (not your DAW integrated renderer), in order to copy the binaural config and then import the ADM into your DAW or
• Create a DAMF utilising DACT (however, this can only be utilised in the external Renderer software, not a DAWs integrated renderer)

Note for gapless transition: Binaural configs can only be copied if each respective session contains equal beds and objects. If you have transitioning objects, note your object count will increase and need to be replicated in order to copy the binaural config.

Empty Objects

Clarify they were intentionally unused and not intended to contain information. Good practice is to purge them where possible, but not a requirement. We do however recommend advising your label representative of the empty objects so these flags can be ingored during the QC process.

LFE (Filter / Level)

A Dolby Atmos mix engineer is not obligated to use LFE. However, it is worth obtaining confirmation from the mix engineer if this was the intention. If they have used it and it has not been filtered or the level appears excessive (appreciate this is subjective, but on many occasions, it has been found to be a calibration issue in the engineer’s studio) then adjust accordingly, with discussion.

Fade In/Out

If the mix engineer has created fade in/out, please make sure they match as closely as possible to the stereo.

Loudness and True Peak Analysis

Please ensure this conforms to the specification of the loudest track not exceeding -18.0 LKFS and that True Peak does not exceed -1.0 dBTP.

Album Balancing

Where relevant, please ensure the loudness of each track has observed respective loudness of stereo versions with your loudest track not exceeding -18.0 LKFS.

Album Sequencing & Duration Matching

Currently, Dolby Atmos playback on Apple and Amazon run side-by-side with the stereo meaning a user can switch between at any point. Therefore, it is important to sequence and confirm all runtimes are correct and no tracks are missing. It is also important to consider, not only matching the duration but that tracks start at the exact timing as the stereo (including if the stereo appears to contain extra silence at the beginning or end because this could be intentional.

Trim and Downmix

A consideration, especially when compiling an album mixed by more than one engineer, is a consistent playback. Therefore, you need to ensure each track has been set to ‘Direct Render’. For music mixing ‘Direct Render’ has been determined as the best setting for translation of mix intent across devices.

Regarding trims, we recommend (but do not mandate) 0 dB on both Surround and Heights. Again, this is more authentic to the mix intention but we also appreciate the increase in amplitude and the concern it creates currently when managing loudness levels. Streaming platforms are continually working to ensure Dolby Atmos products do not appear lower in perceived volume compared to the stereo with many processes already in place (such as Sound Check on Apple devices).

FFOA

For ‘Music Only’ products FFOA (First Frame of Action) must be removed.

Frame Rate

Please ensure all assets are running at 24FPS and if any adjustments are required, this should be conducted through your DAW or DACT maintaining native pitch and time.  

Sample Rate

When assets are delivered with a Sample Rate of 96kHz, this must be retained upon export.

CHECKLIST
Global Gain, EQ & Dynamic Processing
Gapless Transitions
Binaural Metadata
Empty Objects
LFE (Filter / Level)
Fade In/Out
Loudness and True Peak Analysis
Album Balancing
Album Sequencing & Duration Matching
Trim and Downmix
FFOA
Frame Rate
Sample Rate