
L64005 MPEG-2 Audio/Video Decoder Technical Manual
6-33
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
6.9.8
Alignment of
the Bitmap
The color components from the OSD controller must line up with the cor-
responding component from the video stream.
The OSD controller must perform conversion from 4:4:4 data to 4:2:2.
Table 6.11
Conversion from
4:4:4 to 4:2:2
6.9.9
OSD Control
The Group 6, Index 23 OSD Control Register contains bits that control
the OSD operating mode. The OSDE bit in Group 6, Register 23,
enables or disables the OSD controller. VBLK bit in Group 6, Register 23
can force the reconstructed image to black. See the Section
2.8.14 for
details.
The external OSDA pin can enable or disable the OSD controller when
used as an input. It can report on OSD activity when used as an output.
Setting the OSDAM bit in the OSD Control Register congures the OSDA
pin for input, and clearing this bit congures the pin for output.
6.9.10
Limitations in
the OSD
Controller
The following are considered programming errors and are
not checked
by the OSD controller. The results are undened.
The OSD header is not word aligned.
The OSD header includes a row or column number that is out of
range of the current display parameters; this error indicates the end
of the OSD display list.
The row end address is less than the row start address.
The column end address is less than the column start address.
OSD regions overlap each other in any way.
OSD regions are not ordered top to bottom in the display.
The OSDA pointer points to a non existing address or an address
that does not contain a OSD header.
In linked-list mode, the width of an OSD region is not a multiple of
32 pixels (2-bpp mode) or 16 pixels (4-bpp mode).
4:4:4 OSD Data
4:2:2 OSD Data
Y0
Cb0
Cr0
Cb0
Y1
Cb1
Cr1
Cr0
Y2
Cb2
Cr2
Cb2