Line alternative format is defined by the HDMI Specification 1.4a. In general the functionality is:
- Lines from the left and the right frames are interleaved alternatively on the screen to produce a 3D image.
- Required also to support interleaving column-wise to support all possible screen orientations.
The functionality is done in the overlay manager:
- The layers are grouped into two categories based on the z-order: Odd z-order may blend together and will interleave with even z-order pipes, which may blend together.
- Two types of interleaves are possible, line-based interleaving and pixel-based interleaving to support landscape and portrait screen orientations.
The configuration is done from the
DISPC_CONFIG1[29:28] TVINTERLEAVE for the TV output,
DISPC_CONFIG1[27:26] PLCDINTERLEAVE for the primary LCD,
DISPC_CONFIG2[27:26] SLCDINTERLEAVE for the secondary LCD, and
DISPC_CONFIG3[27:26] TLCDINTERLEAVE for the third LCD. The following values apply for the these bitfields:
- 0x0: If zero then no interleaving happens in the overlay manager.
- 0x1: Checkerboard pattern:
- All even pixels on even lines have a contribution from even z-order pipes.
- All odd pixels on even lines have a contribution from odd z-order pipes.
- All even pixels on odd lines have a contribution from odd z-order pipes.
- All odd pixels on odd lines have a contribution from even z-order pipes.
- 0x2: All even lines (all pixels) have a contribution from even z-order pipes. All odd lines (all pixels) have a contribution from the odd z-order pipes.
- 0x3: All even pixels (for all lines) have a contribution from even z-order pipes. All odd pixels (for all lines) have a contribution from the odd z-order pipes.