B.3 Preprocessing

26.1183GPPRelease 17TSVirtual Reality (VR) profiles for streaming applications

B.3.1 Channel Content

Channel input content is converted into a corresponding set of point sources with associated positions using the loudspeaker configuration data included in mpegh3da_getChannelMetadata() and the associated PCM data obtained via the interface specified in B.2.1

B.3.2 Object Content

Object input content is converted into corresponding point sources with associated positions using the metadata included in mpegh3da_getObjectAudioAndMetadata() and the associated PCM data obtained via the interface specified in clause B.2.1

B.3.3 HOA Content

As specified in clause B.2.1 HOA content is input in the ESD representation together with the metadata included in mpegh3da_getHoaMetadata(). As a pre-processing step, the ESD representation is first converted into HOA coefficients. All coefficients associated with HOA of order larger than three are discarded to limit the maximum computational complexity.

B.3.4 Non-diegetic Content

Channel groups for which the gca_directHeadphone flag is set in mpegh3da_getChannelMetadata() are routed to left and right output channel directly and are excluded from binaural rendering using scene displacement data (non-diegetic content). Non-diegetic content may have stereo or mono format. For mono, the signal is mixed to left and right headphone channel with a gain factor of 0.707.

For each channel group it has to be checked in the mpegh3da_getChannelMetadata() if the gca_fixedChannelsPosition flag is equal to 0 or 1. A channel group with an associated ‘gca_fixedChannelsPosition == 1’ is included in the binaural rendering but excluded from the scene displacement processing according to clause B.4, i.e. its position is not updated.

For each object it has to be checked in the mpegh3da_getObjectAudioAndMetadata() if the goa_fixedPosition flag is equal to 0 or 1. An object with an associated ‘goa_fixedPosition == 1’ is included in the binaural rendering but excluded from the scene displacement processing according to clause B.4, i.e. its position is not updated.