Texas Instruments OMAP36 Series, Technical Reference Manual, Page: 1719 / 3738

Readout Start Address for 90° Rotation
= ba + (iw * (ih -1) * ps)
Pixel Increment
= -iw * ps - (ps -1)
Row Increment
= (iw * (ih - 1) * ps) + 1
Buffer Base
Address (ba)
1
2
3
iw
ih
Pixel output Direction
Memory
LCD Screen
iw
ih
dss-097
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Display Subsystem Basic Programming Model
7.5.3.4.1 Image Data Formats
To understand the programming of the rotation mechanisms described underneath, the supported
representations of the image data in memory must also be considered. Differences exist between the
supported formats on the graphics and video pipelines. The graphics pipeline supports RGB and RGB
with a color look-up table (CLUT), whereas the video pipelines support two versions of YUV 4:2:2 and
RGB16. In the case of YUV, the interpolation and color conversion hardware in the video pipelines
converts the image data to the RGB format suitable for the LCD screen.
The graphics pipeline supports:
•
1-, 2- ,4-, and 8-bits-per-pixel color look-up table
• 12-, 16-, and 24-bits-per-pixel RGB
The video pipelines support the following data formats (always 2 bytes/pixel):
•
RGB16
• YUV2
• UYVY
For more information on the graphics data formats, please refer to Section 7.4.2.2 , Graphics Pipeline.
For more information on the video data formats, please refer to Section 7.4.2.3 , Video Pipeline.
In the video pipeline, the YUV 4:2:2 format is converted into a full YUV 4:4:4 format by interpolation of the
chrominance values from neighboring pixels. After this interpolation is completed, the conversion to the
RGB format (suitable for displaying the image on the LCD screen) is performed.
For more information on YUV 4:2:2 to RGB conversion, please refer to Section 7.4.2.3.2 , Color Space
Conversion.
7.5.3.4.2 Image Data from On-Chip SRAM
For image data located in the on-chip SRAM, the DSS DMA is used to perform 90-degree, 180-degree,
and 270-degree rotation. This is done by using the double-indexed addressing mode of the DMA. This
addressing mode allows a pixel and a row increment to be specified. These address increments are used
after each pixel or each row (line), respectively.
Figure 7-120 illustrates the principle steps for a 90-degree
rotation.
Figure 7-120. 90° DMA Rotation Example
1719 SWPU177N – December 2009 – Revised November 2010 Display Subsystem
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