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Module 6.2 – Creating a Dolby Atmos Master File

  • Updated

Introduction 

The Dolby Atmos Renderer is used to record or export a Dolby Atmos master, or to write updated metadata to an existing master. A master can be recorded for the entire duration of a song or punched in/out of by using In and Out points, or by manually punching in and out. 

 

Recording a Master 

A Dolby Atmos mix is recorded to the Renderer in real-time as it plays back from the DAW.  

Prior to recording, verify the settings for the Renderer and the DAW session: 

  • Ensure that the content starts after 00:00:00:00 on the DAW timeline to allow for some pre-roll; master files cannot record across this point, and starting a recording at 0 hours without pre-roll will result in a short delay while the system locks up and recording begins. 
  • Ensure that the Renderer and the DAW session have the same frame rate (fps) and sample rate. If mismatched, change the Renderer frame rate in Driver preferences, and make any changes required in your DAW settings. 
  • It is recommended that re-render processing be disabled prior to recording.  Live re-renders consume significant CPU resources and can potentially cause errors in a recording. 

To record a master using In and Out points: 

  • In the Renderer, choose File > New Master File or press Command+N (Mac) or Ctrl+N (Windows). The Create New Master File dialog box will appear. 

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  • In the dialog box, provide a name and choose a directory location for the master file. 
  • Add FFOA (First Frame of Action) is only applicable if the Master file was created with pre-roll as it can be used to set the start of the encoding process downstream.   In post production workflows this is used to match the start of the Atmos encode with the first frame of the corresponding video. 

          blobid1.png

  • Click Create. The Renderer is now ready for recording. 
    • The file name will display in the top right of the Renderer window; however, the master file set will not be written to disk until the recording process has been completed. 
  • Enable the Sync On/Off button (clock icon) to put the Renderer into chase mode, synchronizing to LTC from your DAW.  

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  • Set the In and Out points for the recording: 
  • In the Record In/Out section, click the associated switch to move it to the down (enabled) position. 

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  • In the In field, set the timecode value where recording should start.  
  • In the Out field, set the timecode value where recording should end. 
  • Click the Record button to enable it. The button will flash red if Record In/Out is enabled or light solid red if Record In/Out is disabled. 
    • The Renderer will create the destination folder on the selected drive when the Record button is first engaged. 

              blobid4.png

  • Begin playback from your DAW to initiate the Renderer record pass. 
    • Be sure to start playback at an appropriate location in the timeline, prior to the identified In point. Recording will not take place if playback begins after the active In point timecode. Five seconds of pre-roll is suggested in order to ensure correct synchronization lock-up between the DAW and Renderer before recording begins. 
    • The record button will light solid when recording begins (or when playback reaches the In point) and will remain solid red until recording stops (or playback reaches the Out point). 
  • When the recording has completed (after the Out point), stop playback from the DAW. 
  • If prompted with a message to add or update the FFOA, do so at this time, or click Cancel. 
  • Note that the master file will always begin from the first In point recorded to disk, and that subsequent drop-ins must join with existing recorded audio. You cannot, for example, start recording at 01:30:00:00 and then go back to lay down audio from 01:00:00:00. Likewise, you cannot lay down a section of audio from 01:00:00:00 to 01:10:00:00, then skip ahead to lay down audio at 01:30:00:00 without first having recorded audio between 01:10:00:00 and 01:30:00:00. 
  • Recording can be performed manually without the use of In and Out points. Begin playback in the DAW, and click the Record button to manually punch in and out of the Master file. Again, ensure there is sufficient pre-roll in the DAW to allow correct synchronization lock-up prior to punching in. It is recommended to punch out in the Renderer prior to stopping playback in the DAW when recording manually to avoid possible audio gaps in the master. 

 

Master File Set Results 

The Renderer creates the master file set in the destination folder specified in the Create New Master File dialog box. This file set includes three separate files: 

  • .atmos: This is the top-level file that provides essential information about the presentation contained in the master file set, in XML format. 
  • .atmos.metadata: This file contains all of the 3D positional coordinates for object audio in the .audio file. 
  • .atmos.audio: This file contains the audio data for all bed signals and objects. It is an interleaved PCM file stored in the Core Audio Format (CAF). 

 

Navigation 

Next:  Module 6.3 – Playback of a Dolby Atmos Master File   

Previous:   Module 6.1 - Module Objectives