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Camera ISP Functional Description
6.4.7.1.14.2.1 Chrominance Suppression
Occasionally, in very bright portions of an image, only one or two of the color channels are saturated,
while the remaining channel(s) are not. This can lead to a false-color effect. One common example is the
appearance of pink where white should be. Chrominance suppression can be used to correct this issue.
Chrominance suppression can be enabled or disabled using the
NOTE: Some details of this feature are not available in the public domain.
6.4.7.1.14.2.2 Contrast and Brightness
The luminance component can be adjusted for contrast (scaling/multiplication) and brightness
(offset/addition). Contrast is set in the
is set in the
PRV_CNT_BRT
6.4.7.1.14.2.3 Downsampling and Output Clipping
The 4:2:2 conversion module converts image data to YCbCr-4:2:2 format by averaging every other Cb and
Cr component in the horizontal direction. Before outputting the data, the preview engine performs clipping
on the YCC components separately. The minimum and maximum threshold values for the Y and C values
are specified using the
reset values of 0xFF for the maximum Y and C values, and 0 for the minimum Y and C values.
6.4.7.1.15 Camera ISP VPBE Preview Write-Buffer Interface
The output of the preview engine may be passed directly to the Resizer
and/or written to memory
If the output is written to memory, the write address (PRV_WSDR_ADDR) and line offset
(PRV_WADD_OFFSET) must be on 32-byte boundaries. The output format of the YCC data is
programmable by setting the
The final width and height of the output vary depending on which processing functions are enabled.
Table 6-40
indicates how many edge pixels/lines are truncated by enabling certain modules in the preview
engine. These values must be subtracted from the input height and width after the averager to determine
the size of preview-engine output.
Table 6-40. Camera ISP VPBE Preview Image Cropping by Preview Functions
Function
Horizontal median filter
Noise filter
CFA (Bayer, Super CCD Honeycom or RGBE)
Color suppression OR luminance enhancement
Maximum total
NOTE: Different CFA modes are mutually exclusive.
6.4.7.2
Camera ISP VPBE Resizer
6.4.7.2.1 Camera ISP VPBE Resizer Features
The Resizer module enables image upsampling and downsampling, see
features are supported:
•
Flexible input sources:
– Preview module: Enables on-the-fly processing
1212
Camera Image Signal Processor
Public Version
PRV_CNT_BRT
[7:0] BRT field (U8Q0 precision).
PRV_SETUP_YC
register. If no clipping is required, the register must be set to its
(PRV_PCR
[20] SDRPORT).
PRV_PCR
[18:17] YCPOS parameter.
Image Cropping by Preview Functions
Copyright © 2009–2010, Texas Instruments Incorporated
PRV_PCR
[16] SUPEN parameter.
[15:8] CNT field (U8Q4 precision), and brightness
(PRV_PCR
Pix/Line
4
4
4
2
14
Table
6-41. The following
SWPU177N – December 2009 – Revised November 2010
www.ti.com
[19] RSZPORT)
Lines
0
4
4
0
8
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