SDK CV Algorithms¶

class Metavision::ActivityFilterAlgorithm¶

Filter that accepts events if a similar event has happened during a certain time window in the past, at exactly the same coordinates.

Public Functions

ActivityFilterAlgorithm(std::uint32_t width, std::uint32_t height, timestamp activity_time_ths, unsigned short activity_ths, timestamp trail_ths)¶

Builds a new ActivityFilterAlgorithm object.

Parameters

width: Maximum X coordinates of the events in the stream
height: Maximum Y coordinates of the events in the stream
activity_time_ths: Length of the time window for activity filtering (in us) (same as for activity_noise_filter)
activity_ths: Minimum number of events in the neighborhood for activity filtering
trail_ths: Length of the time window for trail filtering (in us)

~ActivityFilterAlgorithm() = default¶: Default destructor.

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the Activity filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range

bool operator()(const Event2d &event)¶

Checks if the event is filtered.

Return: true if the event is filtered

template<typename Use64Bits = std::true_type> class Metavision::ActivityNoiseFilterAlgorithm¶

Filter that accepts events if a similar event has happened during a certain time window in the past, in the neighborhood of its coordinates.

Public Functions

ActivityNoiseFilterAlgorithm(std::uint32_t width, std::uint32_t height, timestamp threshold)¶

Builds a new ActivityNoiseFilterAlgorithm object.

Parameters

width: Maximum X coordinate of the events in the stream
height: Maximum Y coordinate of the events in the stream
threshold: Length of the time window for activity filtering (in us)

~ActivityNoiseFilterAlgorithm() = default¶: Default destructor.

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the Activity Noise filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range

timestamp get_threshold()¶

Returns the current threshold.

Return: Threshold applied while filtering

void set_threshold(timestamp threshold)¶

Sets the current threshold.

Parameters

threshold: Current threshold

bool operator()(const Event2d &event)¶

Checks if the event is filtered.

Return: true if the event is filtered

template<typename Converter> class Metavision::EventConverterAlgorithm¶

This algorithm applies the () operator of the Converter class to the input.

Public Functions

constexpr EventConverterAlgorithm(const Converter &converter = Converter())¶

Constructor

Parameters

converter: Instance of the Converter class

class Metavision::EventCounterAlgorithm¶

This class counts the number of events happening during a simulation step

Public Functions

EventCounterAlgorithm(double threshold = 19)¶

Builds a new EventCounterAlgorithm object.

Parameters

threshold: Threshold in average rate for the analog_output overlay in Mev/S

EventCounterAlgorithm(const std::string &output_filename, timestamp step_time, timestamp scaling_time, bool enable_log = true, double threshold = 19., bool compute_variance = false)¶

Builds a new EventCounterAlgorithm object.

Parameters

output_filename: Name of the output file to be generated
step_time: Time interval (in us) used to compute the peak event rate
scaling_time: Time interval (in us) used to compute the average event rate
enable_log: true to save a log file
threshold: Threshold in average rate for the analog_output overlay in Mev/S
compute_variance: true to compute the variance

~EventCounterAlgorithm()¶: Destructor.

void enable_log(bool state)¶

Enables or disables data logging.

Parameters

state: If true, the logging will start, otherwise it will stop

void set_log_destination(const std::string &csv_file_name)¶: Sets the output file.

void set_step_time_us(timestamp step_time_us)¶

Sets step time.

Parameters

step_time_us: Time interval (in us) used to compute the peak event rate during the step time (must be smaller than scaling time). Default is 1 ms.

void set_scaling_time_us(timestamp scaling_time_us)¶

Sets scaling time.

Parameters

scaling_time_us: Time interval (in us) used to compute the average event rate during the scaling time. Default is 1000 ms

void polarity_to_count(int polarity)¶

Counts only the events that have the input polarity. All events are counted by default. Use -1 to disable the filter after setting a value If the event doesn’t have a polarity, the compilation will fail

Parameters

polarity: The polarity to filter

void print_stats()¶: Prints statistics.

std::pair<double, double> get_average_rate()¶

Gets the average rate last computed.

Return: End time (in seconds) of the last average rate that has been computed (first element of the pair) and the average rate (kEv per second) during this interval

std::pair<double, double> get_peak_rate()¶

Gets the peak rate last computed.

Return: Time (in seconds) of the last peak rate that has been computed (first element of the pair) and the average peak rate (kEv per second)

uint64_t get_events_number()¶

Gets number of events.

Return: Total number of events counted from the input producer since the beginning

uint64_t get_events_number_by_polarity()¶

Gets number of events of the polarity set by polarity_to_count.

Return: Total number of events of the polarity set by polarity_to_count counted from the input producer since the beginning

size_t add_callback_on_scale(const std::function<void(double, double)> &cb)¶

Adds a function to be called every time an event rate has been computed.

Return

Callback id

Parameters

cb: Function that takes as input the timestamp (in seconds) of the last event the average event rate has been computed on and the average event rate (kEv per second)

void remove_callback_on_scale(size_t cb_id)¶

Removes the function to call every time an event rate has been computed.

Parameters

cb_id: Callback id

template<typename InputIt> std::enable_if_t<!std::is_base_of<Metavision::Event2d, typename Metavision::iterator_traits<InputIt>::value_type>::value> process(InputIt it, InputIt it_end, timestamp ts)¶

Processes a set of events using iterators.

Note

Two implementations are provided, the first one for events derived from Event2d, the other one for non Event2d-derived events

Parameters

it: Iterator on the first event
it_end: Iterator on the last event
ts: Timestamp of current timeslice

class Metavision::FlowFrameGeneratorAlgorithm¶

Public Functions

template<typename InputIt> void add_flow_for_frame_update(InputIt first, InputIt last)¶: Stores one motion arrow per centroid (several optical flow event may have the same centroid) in the motion arrow map to be displayed later using the update_frame_with_flow method.

void update_frame_with_flow(cv::Mat &display_mat)¶

Updates the input frame with the centroids’ motion stored in the history.

Clears the history afterwards

class Metavision::FrequencyAlgorithm¶

Algorithm used to estimate the flickering frequency (Hz) of the pixels of the sensor.

Public Functions

FrequencyAlgorithm(int width, int height, const FrequencyEstimationConfig &frequency_config)¶

Builds a new FrequencyAlgorithm object.

Parameters

width: Sensor’s width
height: Sensor’s height
frequency_config: Frequency estimation’s configuration

~FrequencyAlgorithm()¶: Destructor.

bool set_min_freq(double min_freq)¶

Sets minimum frequency to output.

Note

The value given has to be < maximum frequency

Return

False if value could not be set (invalid value)

Parameters

min_freq: Minimum frequency to output

bool set_max_freq(double max_freq)¶

Sets maximum frequency to output.

Note

The value given has to be > minimum frequency

Return

False if value could not be set (invalid value)

Parameters

max_freq: Maximum frequency to output

bool set_filter_length(unsigned int filter_length)¶

Sets filter filter length.

Parameters

filter_length: Number of values in the output median filter

void set_difference_threshold(period_precision diff_thresh)¶

Sets the difference allowed between two periods to be considered the same.

Parameters

diff_thresh: Maximum difference allowed between two successive periods to be considered the same

template<class InputIterator, class InsertIterator> void process_events(InputIterator first, InputIterator last, InsertIterator inserter)¶

Processes events.

Parameters

first: iterator to the first event to process
last: iterator to the last event to process
inserter: Output inserter for Event2dFrequency<float>

class Metavision::PeriodAlgorithm¶

Algorithm used to estimate the flickering period of the pixels of the sensor.

Public Types

using period_precision = float¶: Timestamp precision.

Public Functions

PeriodAlgorithm(int width, int height, const PeriodEstimationConfig &config)¶

Builds a new PeriodAlgorithm object.

Parameters

width: Sensor’s width
height: Sensor’s height
config: period estimation’s configuration

~PeriodAlgorithm()¶: Destructor.

bool set_min_period(double min_period)¶

Sets minimum period to output.

Note

The value min_period has to be smaller than the maximum period

Return

false if value could not be set (invalid value)

Parameters

min_period: Minimum period (us) to output

bool set_max_period(double max_period)¶

Sets maximum period to output.

Note

The value max_period has to be larger than the minimum period

Return

false if value could not be set (invalid value)

Parameters

max_period: Maximum period to output

bool set_filter_length(unsigned int filter_length)¶

Sets filter filter length.

Parameters

filter_length: Number of values in the output median filter

void set_difference_threshold(period_precision diff_thresh)¶

Sets the difference allowed between two periods to be considered the same.

Parameters

diff_thresh: Maximum difference allowed between two successive periods to be considered the same

template<class InputIterator, class InsertIterator> void process_output(InputIterator first, InputIterator last, InsertIterator inserter)¶

Processes events.

Parameters

first: iterator to the first event to process
last: iterator to the last event to process
inserter: Output inserter for Event2dPeriod<T>

class Metavision::RoiMaskAlgorithm¶

Class that only propagates events which are contained in a certain region of interest.

The Region Of Interest (ROI) is defined by a mask (cv::Mat). An event is validated if the mask at the event position stores a positive number.

Alternatively, the user can enable different regions (rectangular) defined by the upper left corner and the bottom right corner that propagates any event inside them.

Public Functions

RoiMaskAlgorithm(const cv::Mat &pixel_mask)¶

Builds a new RoiMaskAlgorithm object which propagates events in the given window.

Parameters

pixel_mask: Mask of pixels that should be retained (pixel != 1 is filtered)

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the ROI Mask filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range

void enable_rectangle(int x0, int y0, int x1, int y1)¶

Enables a region (rectangle) defined by the upper left corner and the bottom right corner that propagates any event inside them.

Parameters

x0: X coordinate of the upper left corner
y0: Y coordinate of the upper left corner
x1: X coordinate of the lower right corner
y1: Y coordinate of the lower right corner

int max_height() const¶

Returns the maximum number of pixels (height) of the mask.

Return: Maximum height of the mask

int max_width() const¶

Returns the maximum number of pixels (width) of the mask.

Return: Maximum width of the mask

const cv::Mat &pixel_mask() const¶

Returns the pixel mask of the filter.

Return: cv::Mat containing the pixel mask of the filter

void set_pixel_mask(const cv::Mat &mask)¶

Sets the pixel mask of the filter.

Parameters

mask: Pixel mask to be used while filtering

template<typename T> bool operator()(const T &ev) const¶

Basic operator to check if an element is filtered.

Parameters

ev: Event to be checked

bool operator()(int x, int y) const¶

Basic operator to check if a position is filtered.

Parameters

x:
y:

class Metavision::RotateEventsAlgorithm¶

class that allows to rotate an event stream.

Note: We assume the rotation to happen with respect to the center of the image

Public Functions

RotateEventsAlgorithm(std::int16_t width_minus_one, std::int16_t height_minus_one, float rotation)¶

Builds a new RotateEventsAlgorithm object with the given width.

Parameters

width_minus_one: Maximum X coordinate of the events (width-1)
height_minus_one: Maximum X coordinate of the events (height-1)
rotation: Value in radians used for the rotation

~RotateEventsAlgorithm() = default¶: Default destructor.

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the rotate event filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range

std::int16_t width_minus_one() const¶

Returns the maximum X coordinate of the events.

Return: Maximum X coordinate of the events

void set_width_minus_one(std::int16_t width_minus_one)¶

Sets the maximum X coordinate of the events.

Parameters

width_minus_one: Maximum X coordinate of the events

std::int16_t height_minus_one() const¶

Returns the maximum X coordinate of the events.

Return: Maximum X coordinate of the events

void set_height_minus_one(std::int16_t height_minus_one)¶

Sets the maximum X coordinate of the events.

Parameters

height_minus_one: Maximum X coordinate of the events

void set_rotation(const float new_angle)¶

Sets the new rotation angle.

Parameters

new_angle: New angle in rad

class Metavision::SparseOpticalFlowAlgorithm¶

Public Functions

template<typename InputIt, typename OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the optical flow algorithm to the given input buffer storing the result in the output buffer.

Note

the available implementations provided are:

InputIt = std::vector<Event2d>::iterator, OutputIt = std::back_insert_iterator<std::vector<EventOpticalFlow>>
InputIt = std::vector<Event2d>::const_iterator, OutputIt = std::back_insert_iterator<std::vector<EventOpticalFlow>>
InputIt = std::vector<Event2d>::iterator, OutputIt = std::vector<EventOpticalFlow>::iterator
InputIt = std::vector<Event2d>::const_iterator, OutputIt = std::vector<EventOpticalFlow>::iterator
InputIt = const Event2d *, OutputIt = EventOpticalFlow *

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range.

struct Parameters¶

Public Members

int width¶: Spatial dimensions of the input stream of events.

template<class itype> class Metavision::SpatioTemporalContrastAlgorithmT¶

The SpatioTemporalContrast Filter is a noise filter using the exponential response of a pixel to a change of light to Filter out wrong detections and trails.

For an event to be forwarded, it needs to be preceded by another one in a given time window, this ensures that the spatiotemporal contrast detection is strong enough. It is also possible to then cut all the following events up to a change of polarity in the stream for that particular pixel (strong trail removal). Note that this will remove signal if 2 following edges of the same polarity are detected (which should not happen that frequently).

Note: The timestamp may be stored in different types 64 bits 32 bits or 16 bits. The behavior may vary from one size to the other since the number of significant bits may change. Before using the version with less than 32 bits check that the behavior is still valid for the usage.

Public Functions

SpatioTemporalContrastAlgorithmT(int width, int height, timestamp threshold, bool cut_trail = true)¶

Builds a new SpatioTemporalContrast object.

Parameters

width: Maximum X coordinate of the events in the stream
height: Maximum Y coordinate of the events in the stream
threshold: Length of the time window for filtering (in us)
cut_trail: If true, after an event goes through, it removes all events until change of polarity

template<typename InputIt, typename OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Processes events.

Parameters

first: Beginning of the Buffer range
last: End of the Buffer range
d_first: Beginning of the destination range

template<typename TTimestampType> class Metavision::TTrailFilterAlgorithm¶

Filter that accepts an event either if the last event at the same coordinates was of different polarity, or if it happened at least a given amount of time after the last event.

Public Functions

TTrailFilterAlgorithm(uint16_t width, uint16_t height, TTimestampType threshold)¶

Builds a new TTrailFilterAlgorithm object.

Parameters

width: Maximum X coordinate of the events in the stream
height: Maximum Y coordinate of the events in the stream
threshold: Length of the time window for activity filtering (in us)

~TTrailFilterAlgorithm() = default¶: Default destructor.

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the Trail filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Template Parameters

InputIt: Read-Only iterator with Event2d base class
OutputIt: Read-Write iterator with Event2d base class

Parameters

first: Beginning of the input iterator
last: Ending of the input iterator
d_first: Output iterator

TTimestampType get_threshold() const¶

Returns the current threshold.

Return: Threshold applied while filtering

void set_threshold(TTimestampType threshold)¶

Set the current threshold.

Parameters

threshold: Current threshold

bool operator()(const Event2d &event)¶

Check if the event is filtered.

Return: true if the event is filtered

class Metavision::TransposeEventsAlgorithm¶

TransposeEventsAlgorithm is a class that switches X and Y coordinates of an event stream. This filter changes the dimensions of the corresponding frame (width and height are switched)

Public Functions

template<class InputIt, class OutputIt> OutputIt process(InputIt first, InputIt last, OutputIt d_first)¶

Applies the Transpose filter to the given input buffer storing the result in the output buffer.

Return

Iterator pointing to the last + 1 event added in the output

Parameters

first: Beginning of the range of the input elements
last: End of the range of the input elements
d_first: Beginning of the destination range

void operator()(Event2d &ev) const¶

Applies the Transpose filter to the given input buffer storing the result in the output buffer.

Parameters

ev: Event2d to be updated