SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The two transparency color keys are the source transparency color key and the destination transparency color key. The transparency color key can be used only with RGB formats (ARGB, RGB, RGBA, xRGB, and RGBx). in this case the A information is ignored for the comparison between the pixel value and the color key value. It is possible to use YUV formats with some care because the comparison is between the input pixel value of the overlay manager from pipeline (GFX or one of the VID pipelines depending on the Z-order) and the color key value. The YUV data is converted to RGB format. If the original format is YUV, the user must consider the color space conversion processing to define the RGB color key value used for the comparison.
The transparency color key is enabled by setting the following bits to 0x1:
The transparency color key is determined in the following bit fields.
The video source transparency color key and graphics destination transparency color key cannot be active at the same time.
The value of the video source transparency color key defines the encoded pixel data considered as a transparent pixel. The encoded pixel values with the source color key value are not visible, and the encoded pixel values of the under layers or solid background color are visible (the pixel alpha blending value of layer 4 is forced to 0x00, fully transparent).
The scaler can be enabled as a preprocessor in the VID pipeline, but it is necessary to consider the pixel scaling preprocessing in order to define the color key value to be used after the rescaling for the comparison between the input pixel value to the overlay manager and the color key value.
The source transparency color key mode is selected by setting the following bits to 0x1:
Figure 11-77 shows an example of source color key. The pixels with the transparency color key are not displayed; instead, pixels of the resulting layer underneath are shown.
The graphics destination transparency color key value defines the encoded pixels in layer 1, which are not displayed. Other layer 1 pixels (nonequal to destination transparency color key) are displayed over layer 2. The encoded pixel values with the destination color key value are pixels not visible on the screen because pixels at the same position in layer 2 are visible; otherwise, encoded pixels are visible above layer 2 . The destination transparency color key applies only if layer 1 overlaps layer 2 (see the Z-order section for details on layer position depending on the Z-order parameter in Section 11.2.4.13.1.1, Priority Rule); otherwise, the destination transparency color key is ignored.
The scaler can be enabled as a preprocessor in the VID pipeline. It is necessary, however, to consider the pixel scaling preprocessing in order to define the color key value to be used after rescaling for the comparison between the input pixel value to the overlay manager and the color key value.
The destination transparency color key mode is selected by setting the following bits to 0x0:
Figure 11-78 shows an example of the destination color key. The pixels, equal to the transparency color key, are not displayed and are replaced by layer 2 pixels. All other layer 1 pixels, different from the transparency color key, are displayed over layer 2.