A longterm solution for this issue is under investigation but workarounds are available by using an Aggregate Device comprised of the Dolby Audio Bridge and external device for the renderer output, or separate Aggregate Devices for input and output of the renderer.



Aggregate devices are created in the Audio Device page of Audio MIDI Setup via the “+” icon in the lower right corner.  Aggregate devices should be renamed Input or Output to reflect their function.


Prerequisites for these workarounds:

  • Ensure latest HDX driver installed and check it appears in Audio Midi setup. If it does not restart your machine.  If HDX driver does not appear in the Audio MIDI list it could be because Pro Tools is still using it in the Playback Engine (by default) so first make sure DAB is selected in Pro Tools Playback Engine and if HDX driver still does not appear then restart your machine.
  • Ensure Pro Tools and the Renderer are both closed before creating any aggregate devices.
  • Always ensure re-renders and headphone outputs above the channel count of external hardware are disabled to avoid a feedback loop.




Workaround to be used if external hardware does not have a reliable internal clock and cannot be clocked externally

Playback Engine

Renderer Input

Renderer Output

Aggregate Input “use” Selection Order - 1st 

Aggregate Input  “use” Selection Order - 2nd 

Aggregate Input Clock Source

Aggregate Input Drift Correction

Aggregate Output “use” Selection Order - 1st

*

Aggregate Output “use” Selection Order – 2nd *

Aggregate Output Clock Source

Aggregate Output Drift Correction

Dolby Audio Bridge

Dolby Audio Bridge

Aggregate Output

NA

NA

NA

NA

External Hardware

Dolby Audio Bridge

Dolby Audio Bridge

External Hardware

 

Workaround to be used if external hardware can be clocked to an external source (word clock or video reference)

Playback Engine

Renderer Input

Renderer Output

Aggregate Input “use” Selection Order - 1st 

Aggregate Input  “use” Selection Order - 2nd 

Aggregate Input Clock Source

Aggregate Input Drift Correction

Aggregate Output “use” Selection Order - 1st

*

Aggregate Output “use” Selection Order – 2nd 

*

Aggregate Output Clock Source

Aggregate Output Drift Correction

Dolby Audio Bridge

Aggregate Input

Aggregate Output

Dolby Audio Bridge

External Hardware

External Hardware

Both

Unchecked

External Hardware

Dolby Audio Bridge

External Hardware

Dolby Audio Bridge

 

 * This is the order in which "use" is checked and not the physical order of the list of audio devices.