Conversion for Dolby Atmos and Auro3D
The eight channels of the ORTF-3D are L, R, LS, RS for the lower level, and Lh, Rh, LSh and RSh for the upper level. They are routed to eight discrete playback channels without matrixing.
The center channel remains unoccupied. A center channel is seldom desired in ambience recording; it would distort the energy balance between front and rear, and require significantly greater distances among microphones in order to maintain the necessary signal separation. If a center signal should be necessary for a specific reason, e.g. to cover the shutoff of a reporter's microphone, a simple downmix of the L and R signals at low level is sufficient.
In Auro3D the loudspeaker channels L, R, LS, RS, HL, HR, HLS and HRS are fed.
With Dolby, the integration in the Atmos production environment is equally simple; the channels L, R, LS, RS are simply laid down in the corresponding channels of the surround level, the so-called "Atmos bed," whereas the four upper channels are placed as static objects in the four upper corners of the Cartesian space in the Atmos panning tool. These are then rendered in playback through the corresponding front or rear loudspeakers.
The screen capture from ProTools, with the four Atmos panners as well as the monitoring application, illustrates this.
Fig. 8: Routing of the eight channels from the ORTF-3D in Dolby Atmos (ProTools plugin)