The vvas_xtilecompositor plug-in aggregates four video tile streams into
one packed RGB or BGR output frame. It coordinates DMA-BUF-backed tile views
and a VVAS/XRT master buffer for zero-copy multi-camera composition.
The plug-in uses a fixed 2x2 layout. Four request sink pads provide tiles
sink_0 through sink_3; the source pad produces the composed frame.
For insight into the implementation details, refer to the
vvas_xtilecompositor source code located at
<vvas>/vvas-gst-plugins/gst/xtilecompositor/.