Active Pixel Detection

This tool enables the detection of active pixels from your event-based sensor array, and for the GenX320 model, it also allows you to disable those pixels using an ROI mask.

The source code of this tool can be found in <install-prefix>/share/metavision/sdk/stream/cpp_samples/metavision_active_pixel_detection when installing Metavision SDK from installer or packages. For other deployment methods, check the page Path of Samples.

Procedure

The detection phase is initiated by the user and continues until one of two conditions is met: either the minimum duration (100ms by default) is reached, or the minimum number of events (100,000 by default) is acquired. After the detection is complete, the user can fine-tune the threshold using a slider. Active pixels are defined as those that register more events than the set threshold during the acquisition. Therefore, as the threshold is increased, fewer pixels are classified as active, allowing for precise control over the detection sensitivity.

The detection phase concludes with the generation of a “calibration file”, which contains a comprehensive list of all detected active pixels. For an example of this file format, refer to the section Calibration Data below.

For Prophesee EVKs based on the GenX320 sensor, the generated calibration file is seamlessly integrated by the camera plugin, which leverages the pixel coordinates to create a Region of Interest using the Pixel Mask specification mode. This process is fully automated and transparent to the user, requiring no additional configuration, provided the calibration file is stored in the default directory.

For other sensors (Gen3.1, Gen4.1 and IMX636), the active pixels can be masked thanks to I_DigitalEventMask as shown in metavision_hal_showcase.

Expected Output

Here is the output of the tool once the acquisition phase is done on an EVK3 GenX320:

Expected Output from Metavision Active Detection Sample

How to start

You can directly execute pre-compiled binary installed with Metavision SDK or compile the source code as described in this tutorial.

To start the application, run:

Linux

metavision_active_pixel_detection

Windows

metavision_active_pixel_detection.exe

To check for available options:

Linux

metavision_active_pixel_detection -h

Windows

metavision_active_pixel_detection.exe -h

Calibration data

As previously mentioned, the calibration data is stored in a .txt file. Below is an example of the file’s contents, demonstrating the detection of four active pixels:

% active_pixels_count 4
% active_pixels_percentage 0.003906
% bias_diff 51
% bias_diff_off 21
% bias_diff_on 25
% bias_fo 29
% bias_hpf 0
% bias_refr 10
% date 2023-11-27 17:51:00
% illumination 89
% max 87168.000000
% mean 0.980137
% stddev 273.519189
% temperature 27
% threshold 821.537704
% end
279 32
31 69
90 201
250 264