Dolby Atmos Master File (DAMF)

• The Dolby Atmos Renderer records up to 128 inputs.
• These include Bed and Object audio, OAMD, Binaural, Downmix, and Trim metadata, as well as Input and Re-render configurations.
• These inputs are recorded to a Dolby Atmos Master File set (DAMF).
• DAMF is the native format for the Dolby Atmos Renderer.
• DAMF recordings are comprised of a three-file set.

The three files sets are

• .atmos
• .atmos.metadata
• .atmos.audio

.atmos file

• It is an XML file containing information about the Dolby Atmos presentation.
• It also includes index information about the other files in the file set.
• This file specifies the number of inputs used as Beds or Objects.
• It specifies frame rate, file start, first frame of action.
• It specifies the number of elements used in spatial coding, downmix, and trim metadata.

.atmos.metadata file

• It is an XML file which contains dynamic positional and size OAMD for each Object along with binaural metadata settings.

.atmos.audio file

• It is a Core Audio Format (CAF) file.
• It can have up to 128 tracks of interleaved audio.
• Opening the .atmos and .atmos.metadata files is possible with a text editor for inspection.
• Direct editing is not advised with the file set as it can become corrupted.

ADM BWF

• ADM BWF (Audio Description Model Broadcast Wav Format) is an alternative Dolby Atmos master format.
• ADM BWF is sometimes referred to as ADM BWAV.
• All the information in the .atmos and .atmos.metadata files is in a data chunk in the header of the wav file.
• The audio payload itself is up to 128 tracks of interleaved audio.

Advantages of ADM BWF

• It is a single file instead of three files in a folder, making it easy to interchange with other facilities.
• It can be imported into the DAW.
• It allows all Bed and Object audio tracks to be recreated along with all the panning metadata.
• It allows for language replacement, timing conformance, and censorship edits prior to remastering.
• ADM BWF can be encoded to Dolby True HD, Dolby Digital Plus JOC, and Dolby AC-4 IMS.
• It is the primary deliverable to streaming operators and Blu-ray authoring.

IMF.IAB

• It is a mezzanine format for IMF (interoperability mastering format).
• IAB is considered a mezzanine format rather than a master format, as OAMD is quantized.
• IAB.mxf is used by third-party IMF packaging tools to create a delivery container for both Dolby Atmos and video (including Dolby Vision).
• The Dolby Atmos Renderer natively records in the .atmos format only.
• It can convert to and export ADM BWF and IAB.MXF and perform basic top/tail edits.
• The Dolby Atmos Renderer can also open ADM BWF and IAB.MXF files as master files for playback, QC, basic top/tail editing, conversion (between the two formats), and re-export.
• Some restrictions apply with open ADM BWF and IAB.MXF.
• Punch-in and other metadata editing are not permitted with ADM BWF and IAB.MXF.
• Conversion to .atmos from ADM BWF and IAB.MXF is not permitted.
• DACT (Dolby Atmos Conversion Tool) is a companion application to the Dolby Atmos Renderer.
• It is required to convert from ADM BWF and IAB.MXF to .atmos, perform format and frame-rate conversions, as well as perform complex editing operations on master files.
• DACT (Dolby Atmos Conversion Tool) is a free utility.

Technical Delivery Specifications

• The deliverables required by streaming services are spelled out in technical delivery specifications.
• These vary in terms of loudness and peak target, the number and format of master files and channel-based deliverables, as well as naming conventions.
• Some specifications ask for DAW sessions along with ADM BWF for archival purposes.
• Being aware of the deliverables required is crucial to achieving an efficient workflow.