Netflix content supports the encoding and distribution of Dolby Atmos immersive sound. With up to 128 audio channels, Atmos gives creatives more flexibility to create a dynamic sound design.
Setting up a Room
To begin, you must have a room that is capable of playing back Dolby Atmos BWAV ADM files of IAB MXF essences. These are usually very large (~50-70GB) and contain all the bed and object channels (up to 128) that are supported in Atmos.
You’ll be able to download the Atmos file from Asset QC along with a proxy of the IMF or the IMF package as a whole, including the IAB essence and full resolution video essence files.
Atmos mixes should be in sync from the beginning of the IMF. If the Atmos must be adjusted to sync with the IMF, that should be noted as a blocker in the QC report.
Once all files are downloaded, you will need to playback on a computer system that has the following programs and minimum abilities:
- Mac Pro or Windows PC with 32GB of RAM and local storage of at least 500GB
- External Storage connection or drive.
- Latest version of Pro Tools Ultimate or Compatible IAB IMF playback/mastering tool
- Dolby Atmos Production Suite
- Dolby Atmos Renderer
- Dolby Atmos Monitor
- An audio output unit that can support at least 16 channels out
- Any Pro Tools compatible audio unit with 16 analog, digital or MADI connections will work.
- Examples: MOTU 16A, Avid 192, Avid MTRX
- 12 powered speakers - L, R, C, LFE, LSS, RSS, LRS, RRS, LTS, RTS, LTR, RTR
- A room with speakers arranged in at least a 7.1.4 arrangement
- A monitor management unit between the amps and Pro Tools to isolate signals and set reference level.
- A Video or second Computer monitor to view picture reference while QCing.
This room should be calibrated to the same audio specifications as a 5.1 room, with a reference level of -79 spl.
Atmos BWAV ADM files and IAB MXF files should be at a 48 Khz sample rate with a 24 bit depth. The number of tracks can vary depending on the number of objects used. Atmos mixes may employ any number of 5.1, 7.1 or 7.1.2 beds and any number of objects. Beds and objects may not exceed 128 channels.
Importing a BWAV File into Pro Tools
Netflix can supply you with a Pro Tools session template to get started, if needed. You will have to adjust the I/O settings to match your setup, but all other aspects should be ready to go.
To start a QC, first you must import the BWAV file.
To do so, go to File → Import → Import Session Data. This will open a dialogue box and you can select the BWAV you have been supplied. Under Custom Data at the bottom, select “Object Pan Data.” Select all the tracks available and click Import.
The file will then process and depending on the number of the tracks could take between 20-30 minutes. Pro Tools breaks apart the track beds and objects and copies them into individual WAV files. It is important to have the project file pointed to a sufficient storage location, as the copied files can get fairly large. The metadata track will be input into the necessary tracks.
Double check the output to make sure the correct channels are being sent to the correct speakers and adjust the I/O settings to make the outputs correct.
Before Starting QC
- Import the Video Proxy - ProRes, .MP4, or AVID DnX format
- You will be provided a video proxy to confirm sync against
- Import the video as a new track in Pro Tools
- Check the object tracks to see if automation metadata has been applied
- Do this by expanding the automation section of the object tracks and you should see lines underneath, along with dots noting where automation points are to occur.
- If you do not see automation, please place a support ticket to inform the Asset Management team about this.
- Make sure dialogue is coming out of the center channel from channel 3
- Playback several sections to make sure the system can output the video and audio at full speed.
Importing an IAB file into an IMF Mastering Tool
- Once download of the complete IMF package has completed, open the CPL with your compatible mastering tool of choice.
- Drop the Video essence and IAB essence on the timeline
- Ensure both are in sync with each other by checking several points.
- Make sure that the output rendering is set to the speaker arrangement of your room (minimum 7.1.4)
- Remove distractions from the QC space and begin your QC review!
The QC Review
For Atmos QC, we require a full pass of the audio content with the video, very similar to our 5.1 QC method. Since there is no 2.0 to check, please instead spot check sections of heavy object usage, isolate the channels and make sure that the information contained matches the action on screen.
A full QC pass of the Atmos audio is defined as:
- Fully watching down the content at full speed with all channels enabled.
- Please note any technical issues or content inconsistencies in the Atmos mix, as per Source QC guidelines.
- Noting issues such as, but not limited to audio ticks, pops, channel mismapping, audio compression, extraneous noise and object panning errors. Please refer to the QC Error Code Glossary for more possible issues.
- They must be noted in an itemized fashion, with a timecode in, timecode out, error code and error description (including channel or object where issue occurs).
- Spot checking areas of object usage
- For example, action happening on the right side of frame or off screen right, occurs in right or right overhead channels in the Atmos mix.
- Ensuring that the objects included match on screen action and panning is accurate
Atmos QC should be done through the Asset QC tool, which is where all flagged issues should be entered. If there are any problems accessing the files, entering results, or if there are general questions, please reach out to the support team using the ? icon in the upper right hand corner of the screen.