Pixel Addressing

Supported by ...

All Pixelink Cameras

* Older version of this API only supported 2 parameters; fValue and fMode. This version, and subsequent versions of this API, support all 4 parameters. The additional 2 parameters (fHorizontalValue and fVerticalValue) were added to support asymmetric pixel addressing. That is, the ability to specify a different pixel reduction factor for the horizontal and vertical dimensions. Note however, not all cameras support asymmetric pixel addressing. Use PxLGetCameraFeatures or PxLGetFeature for FEATURE_PIXEL_ADDRESSING, to determine if your particular camera supports asymmetric pixel addressing. If either of these functions indicates that this feature only takes 2 parameters, than your camera does NOT support asymmetric pixel addressing.

Description

The Pixel Addressing feature reduces the number of pixels that are read from the ROI.

Pixel Addressing is controlled by two parameters – a Pixel Addressing mode and a value.  

The Pixel Addressing mode determines how the number of pixels is reduced. The mode of Pixel Addressing can be decimate (0), averaging (1), binning (2) or resampling (3).

The Pixel Addressing value can be considered as the size of a block of pixels that will be reduced to a 2x2 group. With a Pixel Addressing value of 1, the Pixel Addressing mode has no effect and all pixels in the ROI will be returned.  For Pixel Addressing values greater than 1, the number of pixels will be reduced by the square of the value. For example, a Pixel Addressing value of 3 will reduce a 6 x 6 block of pixels to a 2 x 2 block – a reduction of 4/36 or 1/9.

The decimate mode will drop all the pixels in the block except for the top-left group of four. At the highest Pixel Addressing value of 6, a 12 x 12 block of pixels is reduced to 2 x 2. At this level of reduction detail in the scene can be lost and color artifacts introduced.

The averaging mode will average pixels with the similar color within the block resulting in a 2x2 Bayer pattern. This allows details in the blocks to be detected and reduces the effects of color artifacts.  

The binning mode will sum pixels with similar color within the block reducing the block to a 2x2 Bayer pattern. Unlike binning with CCD sensors, this summation occurs after the image is digitized so no increase in sensitivity will be noticed but a dark image will appear brighter.

If your camera supports asymmetric pixel addressing (see "Supported by" for a description), then you can specify different factors to be applied to the horizontal and vertical dimensions. Note that the same pixel addressing mode is applied to both dimensions.

The resampling mode uses a different approach involving the conversion of the Bayer pattern in the blocks to RGB pixels. With a Pixel Addressing value of 1, resampling has no effect. With a Pixel Addressing mode of 2 or more, resampling skips a bayer to RGB conversion step and converts the block of 10-bit pixels to one 30-bit RGB pixel by averaging the red, green and blue channels. Setting the video format to YUV422 mode will result in the best image quality while resampling. Resampling will create images with the highest quality and the least artifacts.

Pixel Addressing will reduce the amount of data coming from the camera. However, only the Decimate mode will permit an increase in the frame rate. Averaging, binning and resampling modes will have the same frame rate as if the Pixel Addressing value was 1 (no decimation.)

Pixel Addressing works in the same fashion with color or monochrome sensors.

API Control

PxLGetFeature, PxLSetFeature

Note:  FEATURE_PIXEL_ADDRESSING and FEATURE_DECIMATION are equivalent. FEATURE_DECIMATION is a legacy term used by the API.Pixel Addressing.

Note: The stream state must be off (STREAM_OFF) to modify this feature. See PxLSetStreamState.

Note: Older version of this API only supported 2 parameters; fValue and fMode. This version, and subsequent versions of this API, support all 4 parameters. The additional 2 parameters (fHorizontalValue and fVerticalValue) were added to support asymmetric pixel addressing. That is, the ability to specify a different pixel reduction factor for the horizontal and vertical dimensions. Note however, not all cameras support asymmetric pixel addressing. Use PxLGetCameraFeatures or PxLGetFeature for FEATURE_PIXEL_ADDRESSING, to determine if your particular camera supports asymmetric pixel addressing. If either of these functions indicates that this feature only takes 2 parameters, then your camera does NOT support asymmetric pixel addressing. Please note that some cameras will return 4 parameters for this feature and still not support asymmetric pixel addressing, such as the PL-D725. 

Note: When fValue is set to 1, fMode may default to 2 (or binning), regardless of the mode set. There is no difference between binning and decimation when fValue is set to 1. 

Feature Flags

Parameters