Note
If you acquired a sensor or an EVK from Prophesee, you can find datasheets and user manuals in our Knowledge Center once you will have requested an account. In this page, we give complementary information about sensor’s ESP.
For all purposes, kindly note that it is now possible to save/load the state of the following ESP functions. This can be achieved via Studio
(load/save settings buttons) or using Camera class
functions bool save() const
and bool load()
(demonstrated in metavision_viewer sample).
Event Signal Processing
Some of the Prophesee’s sensors provide an Event Signal Processing (ESP) block that provide some event filtering features:
Anti-Flicker (AFK) that removes flicker (often considered as noise)
Event Trail Filter (STC and Trail) that removes redundant events
Event Rate Control (ERC) that adjusts the events spatially and temporally to maintain the event rate below the maximum processing capacity
Anti-Flicker (AFK)
The anti-flicker function detects and cancels flicker events in 4x4 divided pixel regions on Gen4.1 and IMX636 sensors. It is a countermeasure for events generated due to light source with flicker such as fluorescent light. The flicker to be canceled can be set in the range of 2 ms to 20 ms period (50 Hz to 500 Hz).
In Metavision Studio, AFK can be configured (if available on your camera):

The AFK can also be enabled using HAL and SDK Driver API:
HAL C++ API:
Metavision::I_AntiFlickerModule
facilityHAL Python API:
metavision_hal.I_AntiFlickerModule
SDK Driver C++ API:
Metavision::AntiFlickerModule
class
Note that Metavision SDK CV module also provides a pure software algorithm that is mostly equivalent to this hardware filter:
C++ API:
Metavision::AntiFlickerAlgorithm
demonstrated in Data Rate C++ applicationPython API:
metavision_sdk_cv.AntiFlickerAlgorithm
demonstrated in Data Rate Python sample
Event Trail Filter (STC/Trail)
Gen4.1 and IMX636 sensors have a filter to cancel redundant information. This filter considers successive events of the same polarity generated in a short time as burst, and will remove some of the events depending on the chose option:
Spatio-Temporal-Contrast (STC) retains the second event of a burst. Hence, STC filters out isolated events. STC comes in two versions (STC_CUT_TRAIL and STC_KEEP_TRAIl) that allows to choose if the trail of events after the second one should be removed (CUT) or kept (KEEP).
TRAIL retains the first event of a burst after a polarity transition and cancels events of the same polarity that are generated within the Trail threshold period.
Burst event filtering drastically reduces the event rate but it also removes texture information. The time range supported by both filters for treatment as a burst event is 1 ms to 100 ms.
In Metavision Studio, STC and TRAIL can be configured (if available on your camera):

The Event Trail filter can also be enabled using HAL and SDK Driver API:
HAL C++ API:
Metavision::I_EventTrailFilterModule
facilityHAL Python API:
metavision_hal.I_EventTrailFilterModule
SDK Driver C++ API:
Metavision::EventTrailFilterModule
class
Note that Metavision SDK API provides algorithms that are mostly equivalent to this hardware filter:
C++ API:
Metavision::TrailFilterAlgorithm
andMetavision::SpatioTemporalContrastAlgorithm
demonstrated in Noise Filtering C++ samplePython API:
metavision_sdk_cv.TrailFilterAlgorithm
andmetavision_sdk_cv.SpatioTemporalContrastAlgorithm
demonstrated in Noise Filtering Python sample
Event Rate Controller (ERC)
The ERC performs adjustment by spatially and temporally dropping events to output at the target event rate on Gen4.0, Gen4.1 and IMX636 sensors. This filter is located in the final stage of the ESP data processing circuit in order to reduce the event rate after AFK and STC/Trail filtering. It is useful to avoid flooding the computing unit with peaks of events, but keep in mind that signal quality will be degraded when filtering is triggered.
In Metavision Studio, ERC can be configured (if available on your camera):

The ERC can also be enabled using HAL and SDK Driver API:
HAL C++ API:
Metavision::I_ErcModule
facilityHAL Python API:
metavision_hal.I_ErcModule
SDK Driver C++ API:
Metavision::ErcModule
class