9-24
Video Interface
The OSD controller supports three basic image formats:
Up to 720 x 576 pixels at 2 bits/pixel
Up to 720 x 576 pixels at 4 bits/pixel
Up to 720 x 576 pixels at 8 bits/pixel
9.9.1 OSD Modes
The host can select the OSD mode by setting the OSD Mode bits in
Register 265 (
page 4-58
).
Table 9.7
shows the coding of the bits.
The internal OSD modes use the on-chip color palette and the OSD
Controller. The external OSD mode simply uses the on-chip color palette
and a color look-up value supplied on the L64105 EXT_OSD pins.
9.9.2 Internal OSD
For internal OSD mode, the host must write a header containing control
information and an optional color palette, and an image bitmap to
SDRAM for each OSD display area. This is best done using an external
DMA Controller.
9.9.2.1 OSD Display Area Storage Layout
Figure 9.13
illustrates the SDRAM word organization of an OSD display
area using 4 bits/pixel resolution. There are four words of control
information followed by a 16-word palette. The palette is followed by the
bitmap image. For 2 bits/pixel resolution, only a 4-color palette is
required. For 8 bits/pixel resolution, a 256-color palette is required. The
pixel data (2, 4, or 8 bits/pixel) is packed with pixel 0 (D0) in the upper
bits of the first word of the bitmap. This layout is repeated for each OSD
display area.
Table 9.7
OSD Modes
OSD Mode Bits
Description
0b00
No OSD (default)
0b01
Internal OSD (Contiguous)
0b10
Internal OSD (Linked List)
0b11
External OSD