VX6953CB datasheet(75/107 Pages) STMICROELECTRONICS

75 / 107 page

8209023 Rev 5

75/107

VX6953CB

EDOF control

8.5

Video modes and EDoF

Setting a video mode implies targetting a reduction in the image size and an increase of the

frame rate. The ST 5 Mpixel cameras are SMIA profile 2 compliant therefore output images

can be downscaled in both X and Y dimensions either using a digital scaling post EDoF

engine or by subsampling pixels before the EDoF engine.

Downsampling or binning by a factor of two or more in each direction increases the

sharpness enough to remove the need to process the raw image. Therefore image

processing is disabled in Preview mode within the EDoF processor in order to save power

and the image is simply copied on the output. The consequence is that the image must be

subsampled by a factor of 2x2 at least to get distance information and a usable raw image.

To summarize, it is recommended that EDoF is forced to landscape mode when in video:

•

if subsampling or binning is used and output image is at least full size image/4

•

if a scaling+cropping method is used from a full size image to output a smaller image

and output image < (2*full size image)/3

•

for a crop of a full resolution image

8.6

EDoF and white balance

The EDoF reconstruction engine requires the white balance gains to be programmed by the

HOST (by I2C writes) frame after frame to the colour feedback register (0x0B8E-0x0B95) of

the sensor. These white balance gains MUST BE corresponding the WB output ones to

prevent from fringing artefacts. These gains are also used for the sensor adaptive lens

shading correction if enabled.

The white balance gains are required in both preview and Capture modes.

The four host white balance gains to be programmed are listed in Table 42.

Table 42. Color feedback registers [0x0B8C to 0x0B95]

Index

Byte

Data type Default Type

Comment

0x0B8C Hi

colour_temperature

16SR

00.00

Not supported by

VX6953CB

0x0B8D Lo

0x0B8E Hi

host_WB_stats_green_red

16UR

01.00

White balance gains to

be applied by the host.

These stats are used by

the EDOF and the

adaptive AV to estimate

the color temperature of

the scene.

0x0B8F Lo

0x0B90 Hi

host_WB_stats_red

16UR

01.00

0x0B91 Lo

0x0B92 Hi

host_WB_stats_blue

16UR

01.00

0x0B93 Lo

0x0B94 Hi

host_WB_stats_green_blue

16UR

01.00

0x0B95 Lo

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