Decimation#

The Decimation camera feature allows you to reduce the number of sensor pixel columns or rows that are transmitted by the camera.

This procedure is also known as "subsampling". It reduces the amount of data to be transferred and may increase the camera's frame rate.

Using the Feature#

How It Works#

You can choose between horizontal and vertical decimation.

Vertical Decimation#

If you enable vertical decimation, the following applies:

• On mono cameras, if you specify a vertical decimation factor of n, the camera transmits only every nth row. For example, when you specify a vertical decimation factor of 2, the camera transmits row 1, skips row 2, transmits row 3, and so on:

  

• On color cameras, if you specify a vertical decimation factor of n, the camera transmits only every nth pair of rows. For example, when you specify a vertical decimation factor of 2, the camera transmits rows 1 and 2, skips rows 3 and 4, transmits rows 5 and 6, and so on:

  

As a result, the image height is reduced. For example, enabling vertical decimation by 2 halves the image height. The camera automatically adjusts the image ROI settings.

Vertical decimation significantly increases the camera's frame rate.

Horizontal Decimation#

If you enable horizontal decimation, the following applies:

• On mono cameras, if you specify a horizontal decimation factor of n, the camera transmits only every nth column. For example, if specify set a horizontal decimation factor of 2, the camera transmits column 1, skips column 2, transmits column 3, and so on:

  

• On color cameras, if you specify a horizontal decimation factor of n, the camera transmits only every nth pair of columns. For example, if you specify a horizontal decimation factor of 2, the camera transmits columns 1 and 2, skips columns 3 and 4, transmits columns 5 and 6, and so on:

  

As a result, the image width is reduced. For example, enabling horizontal decimation by 2 halves the image width. The camera automatically adjusts the image ROI settings.

Horizontal decimation does not (or only to a very small extent) increase the camera's frame rate.

Configuring Decimation#

To configure decimation:

1. Make sure the camera is idle, i.e., not capturing images.
2. Disable binning, if available.
3. Disable scaling, if available, by setting the scaling factor to 1.
4. To configure vertical decimation, enter a value for the DecimationVertical parameter.
5. To configure horizontal decimation, enter a value for the DecimationHorizontal parameter.

The value of the parameters defines the decimation factor. Depending on your camera model, the following values are available:

• 1: Disables decimation.
• 2, 3, 4, …: Enables decimation by 2, 3, 4, and so on.

For example, setting DecimationHorizontal to 3 enables horizontal decimation by 3.

Considerations When Using Decimation#

Effect on ROI Settings

When you are using decimation, the settings for your image ROIs and auto function ROIs refer to the resulting number of rows and columns.

For example, assume that you are using a camera with a 1280 x 960 sensor. Horizontal decimation by 2 and vertical decimation by 2 are enabled. In this case, the maximum ROI width would be 640 and the maximum ROI height would be 480.

Reduced Resolution

Using decimation effectively reduces the resolution of the camera's image sensor. For example, if you set a camera with a 1280 x 960 sensor to use horizontal decimation by 2 and vertical decimation by 2, the effective resolution of the sensor is reduced to 640 x 480.

Possible Image Distortion

Objects will only appear undistorted in the image if the vertical and horizontal decimation factors are equal. With all other combinations, objects will appear distorted. For example, if you combine vertical decimation by 2 with horizontal decimation by 4, the target objects will appear squashed.

Specifics#

Show all camera models

Sample Code#

// Enable horizontal decimation by 2
camera.DecimationHorizontal.SetValue(2);
// Enable vertical decimation by 2
camera.DecimationVertical.SetValue(2);
// Disable horizontal decimation
camera.DecimationHorizontal.SetValue(1);
// Disable vertical decimation
camera.DecimationVertical.SetValue(1);

INodeMap& nodemap = camera.GetNodeMap();
// Enable horizontal decimation by 2
CIntegerParameter(nodemap, "DecimationHorizontal").SetValue(2);
// Enable vertical decimation by 2
CIntegerParameter(nodemap, "DecimationVertical").SetValue(2);
// Disable horizontal decimation
CIntegerParameter(nodemap, "DecimationHorizontal").SetValue(1);
// Disable vertical decimation
CIntegerParameter(nodemap, "DecimationVertical").SetValue(1);

// Enable horizontal decimation by 2
camera.Parameters[PLCamera.DecimationHorizontal].SetValue(2);
// Enable vertical decimation by 2
camera.Parameters[PLCamera.DecimationVertical].SetValue(2);
// Disable horizontal decimation
camera.Parameters[PLCamera.DecimationHorizontal].SetValue(1);
// Disable vertical decimation
camera.Parameters[PLCamera.DecimationVertical].SetValue(1);

/* Macro to check for errors */
#define CHECK(errc) if (GENAPI_E_OK != errc) printErrorAndExit(errc)
GENAPIC_RESULT errRes = GENAPI_E_OK;  /* Return value of pylon methods */
/* Enable horizontal decimation by 2 */
errRes = PylonDeviceSetIntegerFeature(hdev, "DecimationHorizontal", 2);
CHECK(errRes);
/* Enable vertical decimation by 2 */
errRes = PylonDeviceSetIntegerFeature(hdev, "DecimationVertical", 2);
CHECK(errRes);
/* Disable horizontal decimation */
errRes = PylonDeviceSetIntegerFeature(hdev, "DecimationHorizontal", 1);
CHECK(errRes);
/* Disable vertical decimation */
errRes = PylonDeviceSetIntegerFeature(hdev, "DecimationVertical", 1);
CHECK(errRes);

# Enable horizontal decimation by 2
camera.DecimationHorizontal.Value = 2
# Enable vertical decimation by 2
camera.DecimationVertical.Value = 2
# Disable horizontal decimation
camera.DecimationHorizontal.Value = 1
# Disable vertical decimation
camera.DecimationVertical.Value = 1

You can also use the pylon Viewer to easily set the parameters.