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Netflix content supports the encoding and distribution of Dolby Atmos immersive sound. With up to 128 audio channels in both bed and individual object configurations, Atmos gives creatives more flexibility to create a dynamic sound design. This article serves to outline the recommended hardware/software requirements, room setup, and workflow to successfully perform a QC review of content mixed in Dolby Atmos.  

Dolby Atmos as a Format

Printmaster Mix Dolby Atmos may be delivered as either a BWAV ADM file or an Immersive Audio Bitstream (IAB) MXF track file contained in an IMF package.  These will contain all the bed and object channels (up to 128) and associated metadata required for the Atmos format. 

  • The majority of native Atmos mixes will be delivered to Netflix packaged in the IMF as IAB track files.  However, IF delivered as a separate BWAV ADM and the Asset QC request is a Download mode request, the request will include both the BWAV ADM and an IMF derived Backlot proxy to serve as the video reference.
  • For Printmaster BWAV ADM deliveries, the Atmos mix MUST align exactly with the IMF (proxy) from the first frame of the file to the last frame.  If any manual syncing is required to properly align the BWAV ADM with the provided proxy, this should be flagged as a BLOCKER.  
  • The actual number of channels contained within the delivered Atmos file may vary and whether or not any/all of the channels contain information is dependent on how the sound mixer/mix team has chosen to utilize the Dolby Atmos format.  This is regardless of whether it is delivered as a BWAV ADM or an IAB IMF track file.  IF the Atmos request is a DOWNLOAD mode request, please keep the following in mind (we accept the limitations that exist in reviewing Atmos in a CAST mode request): 
    • Should be 48 Khz sample rate and 24 bit depth (consistent with 2.0 or 5.1 channel-based .WAV deliveries).
    • Beds and objects cannot exceed 128 channels, but not all channels need to be included nor do they need to contain audio information.  
    • Beds may be arranged in 2.0, 5.1, 7.1, or 7.1.2 channel configurations (may also be a mix of any combination of these configurations).

Recommended Hardware/Software and Room Setup

QC room should be capable of playback output of Dolby Atmos BWAV ADM files or IAB IMF track files in a 7.1.4 SMPTE configuration.  

Hardware

  • Output unit supporting at minimum 16 channels out
    • Any unit with 16+ analog, digital, or MADI connections compatible with chosen playback solution.
  • 12 powered studio monitor speakers 
    • SMPTE 7.1.4 layout
      • Left
      • Right
      • Center
      • LFE
      • Left Surround
      • Right Surround
      • Left Side Surround
      • Right Side Surround
      • Left Overhead Front
      • Right Overhead Front
      • Left Overhead Surround
      • Right Overhead Surround
    • Calibrated to reference level of -79dB
  • Monitor management unit between the amps and playback hardware/software to isolate signals and set reference level.
  • IF reviewing an IAB IMF, and HDR/SDR video passes are also included - 
    • Reference-level UHD/HD, HDR/SDR monitor (as applicable to the content type/passes included in the Request).  

Software

  • IAB IMF capable playback option
    • Ex. Colorfront Transkoder 2019 or later (latest build recommended)
    • Ex. R&S Clipster version 6.9.1 or later (latest build recommended)
    • Ex. BMD DaVinci Resolve 17 or later (latest build recommended)
  • BWAV ADM capable playback option
    • Ex. AVID Pro Tools Studio or Ultimate (latest build recommended)
    • Ex. Dolby Atmos Renderer (latest build recommended)
    • Ex. BMD DaVinci Resolve 17 (Fairlight) or later (latest build recommended)

QC Workflow Considerations

  • Atmos QC should adhere to all applicable aspects of the Netflix Branded Content QC SOW and the Definition of Quality.
  • Review should focus on member-impacting issues that are noticeable in the 7.1.4 down mix output.
    • Panning errors, audio dropouts, sync issues, etc. will all be discernible in the 7.1.4 down mix output.
  • QC should not flag beds or objects for being “empty” (i.e. missing any audio information throughout content).  
  • Atmos mixes should adhere to True Peak and Loudness specifications as outlined in the Netflix Post Production Branded Delivery Specification for audio assets. 
    • Atmos mixes should be measured via a 5.1 re-render. 
    • QC tolerances for True Peak are at -1dBFS (as outlined in Loudness and True Peaks: How to Measure and When to Flag) despite the Post Production Branded Delivery Specification of -2dBFS.  This is to account for the slight variances in measurements across different plug-in and enterprise solution options.  

 

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