screenRef parameter appears in
typeDefinition 'Objects' and
the typeDefinition 'HOA' and the
audioPackFormat with the typeDefinition 'HOA'.
It indicates whether the content is screen-related or not. The
audioProgrammeReferenceScreen parameter appears in
audioProgramme and describes the screen which was
used during production.
screenRef flag can be used by a renderer for special processing of all
screen-related objects taking into account the size of a local reproduction
screen compared to the production screen-size.
If a renderer uses the
screenRef flag to enable a special processing, it
should use the reference/monitoring/production screen-size of the currently
audioProgramme as the reference screen.
If the flag is set and no
audioProgrammeReferenceScreen element is included in
the corresponding currently rendered
audioProgramme, the default reference
production/monitoring screen is implicitly defined on the basis of
Recommendation ITU-R BT.1845 –
Guidelines on metrics to be used when tailoring television programmes to
broadcasting applications at various image quality levels, display sizes and
|Azimuth of left bottom corner of screen||29.0°|
|Elevation of the left bottom corner of screen||−17.3°|
|Aspect ratio||1.78 (16:9)|
|Width of the screen||58° (as defined by image system 3840 x 2160)|
These spherical values can be transferred to Cartesian coordinates assuming a reference distance of 1.0 by first transferring the values above to the “standard” azimuth/elevation convention (0° azimuth is in front of the right ear, positive values are counted counter-clockwise; 0° elevation is directly above the head, positive values are counted downwards to the front) and then using the trigonometric functions to gain the Cartesian coordinates. The screen is assumed to have its corners touching the unit sphere. This results in the following values (orientation of the Cartesian coordinate axes):
|X-coordinate of the centre of the screen||0.0|
|Y-coordinate of the centre of the screen||0.8438|
|Z-coordinate of the centre of the screen||0.0|
|Width of the screen||0.9354|
The maths to convert from the polar coordinate screen to Cartesian coordinates is
where is the Y-coordinate of the centre of the screen, is the aspect ratio, and is the polar angle of the screen width.
, where is the Cartesian screen width, and is the polar angle of the screen width.