VG6640 datasheet(24/126 Pages) STMICROELECTRONICS

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Functional description

VG6640, VD6640

24/126

DocID023597 Rev 11

3.2.2

Statistics gathering

The statistics gathering block collects and collates pixel values for use by exposure and

white balance algorithms. The average pixel value and variance are generated for up to

48 zones (across the full field of view).

Histogram data can be collected over a maximum of four regions of interest (ROIs), and

over any or all of the color planes. Each histogram has a resolution of 64 bins, each bin is

16-bits.

3.2.3

Pattern generator

The pattern generator block generates a test pattern that can be used to test the entire HDR

video pipe. The following patterns are available:

•

color bars (plain and fade to 50%)

•

grayscale (horizontal, vertical and diagonal)

•

solid colors

•

test cursors with programmable positions

•

pseudo-random data

•

HDR ramp

3.2.4

HDR rescaling

The HDR rescaling algorithm merges the three exposures for each pixel. Exposure

correction factors are calculated and applied to compensate for non-linearities. The merge

algorithm options ensure that true colors are preserved and flicker and ghost artifacts are

minimized.

3.2.5

Piecewise linear (PWL) compression

The PWL block contains a logarithmic type compression algorithm to reduce the data bit-

depth transmitted and avoid excessive bandwidth requirements. The PWL compression

algorithm is loss-less in the sense that any losses in image quality are below the noise floor

of the image. This is implemented using a 32 point curve resulting in an improved SNR

performance, reduced quantization noise and a more natural image.

3.2.6

Status and trailer lines

The status and trailer lines include frame-by-frame metadata such as:

•

product identification

•

configuration status

•

image statistics including histograms

•

frame counter

The data in the status and data lines is encoded using the SMIA embedded line tagging

mechanism. This mechanism allows the data to be decoded in a generic way. For example,

data tags allow both the I2C index and the value of each register included in the status and

trailer lines to be decoded.

Refer to SMIA 1.0 Part 1: Functional Specification, section 4.9 Embedded Data Line

Formats for further details.

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