Topics covered in this article:
- QC of a Dolby Atmos master file
- QC of an exported Dolby Atmos master file format
- QC of Dolby Atmos master files with third-party tools
- Master file QC listening environment
- QC of channel-based deliverables
- QC of the MP4 export with professional and consumer tools
- QC criteria for Dolby Atmos
QC of a Dolby Atmos Master File
QC can begin as soon as the master file is finalized following a recording.
QC of the master .atmos file set can be performed from the Renderer either as an audio-only playback or synchronized to a proxy or reference video played back from the DAW.
QC of an Exported Dolby Atmos Master File Format
If the deliverable is an ADM BWF export per the delivery specs (with or without pre-/post-roll as required) and open the exported file for the QC pass. While export to ADM BWF is non-destructive, it is still best practice to QC the final deliverable.
Master File QC Listening Environment
Audio QC should be performed in a 7.1.4 listening environment. If performed in a dedicated QC environment, professional monitoring/monitor control should be used in a room with sufficient isolation and Noise Criterion (NC) rating. This does not necessarily need to match the mix environment.
QC of Channel-Based Deliverables
All channel-based deliverables (stereo and/or 5.1) must be QC’ed. This includes full mixes and stems as required. This can be done in the DAW, either using live re-renders or by exporting offline re-renders from the Renderer and importing into the DAW.
Remember that dynamics processing may need to be applied in the DAW to achieve True Peak limits for channel-based deliverables. In this case the results should be bounced to disk and QC’ed as the final deliverable of the channel-based assets.
Third-party playback and automated QC platforms can also be deployed, as per the delivery spec.
QC of the MP4 Export with Professional and Consumer Tools
The Renderer allows for the export of an MP4 file with the Dolby Atmos master file encoded as Dolby Digital Plus JOC. As of Renderer v3.7 the MP4 can contain black 720p video (the default), no video, or custom video. Film and Music encoding modes can be used as appropriate for the content. Film encoding mode allows user selectable encoding at 448kbps or 768kbps to provide parity with common streaming bitrates.
QC of the MP4 (with black or custom video) is possible via several methods including:
- Sideloaded on a USB drive and played back via a Blu-Ray player set to audio passthrough and connected via HDMI to an AVR enabled with Dolby Atmos or soundbar with Dolby Atmos.
- Playback from the Safari browser and “pushed” to an Apple TV4k using Airplay connected via HDMI to AVR enabled with Dolby Atmos or soundbar.
- Playback from an iOS device with AirPods Pro or AirPods Max, using the iOS Files application. You can use AirDrop or iCloud Drive to transfer the file to the iOS device and into the Files app. This will enable you to monitor using the current playback chain on Apple devices (note that you can disable head tracking by going to Settings > Accessibility > AirPods > [AirPods device] > Follow iPhone: OFF).
- Options for streaming playback include (but are not limited to):
- Playback via the Plex server application from a Mac or Windows computer to the Plex Player application on an AppleTV4k connected via HDMI to an AVR enabled with Dolby Atmos or soundbar with Dolby Atmos.
- Streamed from AWS storage packaged as Apple HLS via a Safari browser and “pushed” to an AppleTV4k using Airplay connected via HDMI to an AVR enabled with Dolby Atmos or soundbar with Dolby Atmos.
- Streamed from a Mac or Windows computer configured as an HTTP server with playback of HLS packaged .m3u8 via a Safari browser “pushed” to an AppleTV4k using Airplay or MPEG-Dash packaged .mpd from the VLC application to a Google Chromecast Ultra4k. Either connected via HDMI to an AVR enabled with Dolby Atmos or soundbar with Dolby Atmos.
While the first few methods are straightforward, the others require additional knowledge, effort, and configuration.
Playback on consumer devices allows QC of the mix on a variety of possible listening configurations, including soundbars, a variety of discrete speaker configurations, upward-firing speakers, and Dolby Atmos virtualization with tablets and phones.
QC of the MP4 can also be done on professional applications such as the Dolby Reference Player, with file-based analysis using MediaInfo, and other third-party QC applications.
QC Criteria for Dolby Atmos
QC criteria for Dolby Atmos mixes is a superset of criteria used for channel-based assets. Basic audio QC criteria apply such as:
- File duration
- Sample rate (channel-based assets)
- Bit depth (channel-based assets)
- Conformance with loudness specification (LKFS/LUFS)
- True peak levels (channel-based assets only)
Reporting of QC issues should be done in conformance with the customer requirements re: verbiage, severity, format, etc.
Note that third-party professional QC providers are also sanctioned by some of the leading streaming services.
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