# SDK Core Algorithms¶

template<typename Impl>
class Metavision::AsyncAlgorithm

An asynchronous events processor class.

Here, asynchronous means that the output of the processing is at variable frequency. This is useful when one wants to apply a process on events on the fly, and another specific one when a condition is fulfilled.

As opposed to frames that arrive at a fixed frequency, events are asynchronous. The event rate depends on the activity, and so the rate varies with time. In the context of event-based processing, it is often that one wants to apply a processing to events on the fly (online processing such as filling an histogram for instance) and another process when it is considered that enough events have been received (for example in term of events processed count, or time slice of events).

The only entry point of this algorithm is the public process_events method. This method will then call two internal processing methods (process_online and process_async) that should be defined by the user and be private. While the first one processes all events that are passed to process_events, the latter one is called whenever the asynchronous condition is met.

The asynchronous condition is user defined, and set via the various ‘set’ methods. See Processing for more details.

class MyAsyncProcess: public AsyncAlgorithm<MyAsyncProcess> {
public:
MyAsyncProcess() {
positive_contrast_events_count_ = 0;
negative_contrast_events_count_ = 0;

// Will call process async every 3 events processed
size_t max_events_to_process = 3;
set_processing_n_events(max_events_to_process);
}

private:
template<typename InputIt>
inline void process_online(InputIt ev_begin, InputIt ev_end) {
// Fills a vector of events
events_.insert(events_.end(), ev_begin, ev_end);
for (; ev_begin < ev_end; ++ev_begin) {
if (ev_begin->p == 1) {
++positive_contrast_events_count_;
std::cout << "Positive contrast event count: " << positive_contrast_events_count_ << std::endl;
} else {
++negative_contrast_events_count_;
std::cout << "Negative contrast event count: " << negative_contrast_events_count_ << std::endl;
}
}
}

inline void process_async() {
std::cout << "Events processed: " << get_n_processed_events() << std::endl;
std::cout << "Events buffer size: " << events_.size() << std::endl;

if (positive_contrast_events_count_ > negative_contrast_events_count_) {
process_positive_contrast_change();
} else {
process_negative_contrast_change();
}
positive_contrast_events_count_ = 0;
negative_contrast_events_count_ = 0;
events_.clear();
}

inline void process_positive_contrast_change() {
std::cout << "Got more positive contrast changes, applying positive contrast change process." << std::endl;
// Apply processing to events_
}

inline void process_negative_contrast_change() {
std::cout << "Got more negative contrast changes, applying negative contrast change process." << std::endl;
// Apply processing to events_
}

size_t positive_contrast_events_count_, negative_contrast_events_count_;
std::vector<EventCD> events_;

friend class Metavision::AsyncAlgorithm<MyAsyncProcess>;
};

int main(void) {
std::vector<EventCD> my_events {{0,0,1,0}, {0,0,0,0}, {0,0,1,0}, {0,0,0,0}};
MyAsyncProcess async_process;
async_process.process_events(my_events.cbegin(), my_events.cend());
async_process.flush();

// Expected output:

// Positive contrast event count: 1
// Negative contrast event count: 1
// Positive contrast event count: 2
// Events processed: 3
// Events buffer size: 3
// Got more positive contrast changes, applying positive contrast change process.
// Negative contrast event count: 1
// Events processed: 1
// Events buffer size: 1
// Got more negative contrast changes, applying negative contrast change process.
}


Warning

This class uses a Curiously Recursive Template Pattern design. The input template parameter is expected to be a base of this class and the base class should be declared as friend of the derived class.

Template Parameters
• Impl: The Asynchronous process implementation.

Public Types

enum Processing

Processing types.

Processing policies that define the state to rely on to call the asynchronous process (process_async).

N_EVENTS: event count processing policy. Relies on the number of events processed. N_US: time slice processing policy. Relies on the timestamp of the input events. A time slice T holds events between [(n-1)*T; n*T[. MIXED: a mix between N_US and N_EVENTS processing policy. In this policy, the time slice has priority over the events count. SYNC: synchronous condition. process_async is called at the end of the process_events method. EXTERNAL: Relies on an external condition. process_async is called at each flush call.

Values:

enumerator N_EVENTS
enumerator N_US
enumerator MIXED
enumerator SYNC
enumerator EXTERNAL

Public Functions

void set_processing_n_events(const int delta_n_events)

Function to call process_async every n events.

void set_processing_n_us(const timestamp delta_ts)

Function to call process_async every n microseconds.

void set_processing_mixed(const int delta_n_events, const timestamp delta_ts)

Function to call process_async every n events and n microseconds. The processing is done if at least one of the conditions is filled.

void set_processing_sync()

Function to call process_async after each process online.

void set_processing_none()

Function to only call process_events without calling process_async.

This is especially useful if the condition to trigger the creation of a buffer is independent from the content of the processed events (for instance, an external trigger events, an other algorithm condition, etc.). The user must then call flush when the condition is filled.

void flush()

Function to call process_async and update the internal state of the processing policy accordingly.

template<typename InputIt>
void process_events(InputIt it_begin, InputIt it_end)

Function that is calling process online and process state when necessary.

Parameters
• it_begin: First iterator of the buffer

• it_end: End iterator of the buffer

template<typename InputIt>
void process_events(const timestamp ts, InputIt it_begin, InputIt it_end)

Function that is calling process online and process state when necessary.

Parameters
• ts: End timestamp of the buffer. Used if higher than the timestamp of the last event

• it_begin: First iterator of the buffer

• it_end: End iterator of the buffer

timestamp get_processing_ts() const

Function to get the last processing timestamp.

int get_n_processed_events() const

Function to get the number of processed events since the last call to process async.

template<class Event>
class Metavision::FileProducerAlgorithmT

Public Functions

FileProducerAlgorithmT(std::string filename, bool loop = false, timestamp loop_delay = 0)

Builds a new FileProducerAlgorithmT object.

Parameters
• filename: Name of the file to read data from

• loop: If true, the reading from the file will be looped

• loop_delay: Time interval (in us) between two consecutive loops

~FileProducerAlgorithmT()

Destructor.

template<class OutputIt>
void process(OutputIt d_first, timestamp ts)

Processes events until a given timestamp.

bool is_done()

If all events have been processed, returns true.

timestamp get_time_at(timestamp time_window, bool backward)

Gets the timestamp in a given time window.

Parameters
• time_window: Time difference (in us) with the first (or last) event in the file

• backward: If true, search will be from the end of the file (thus giving time last event - time_window)

void start_at_time(timestamp start_time)

Starts reproducing the file from a given time.

Parameters
• start_time: Start time

uint64_t get_n_tot_ev() const

Gets the total number of events in the file.

void load_to_ram()

int get_width() const

Gets the width of the sensor producer that recorded the data.

Return

Width of the sensor

int get_height() const

Gets the height of the sensor producer that recorded the data.

Return

Height of the sensor

std::string get_date() const

Gets the date.

Return

String of the form YYYY-MM-DD h:m:s (example: 2017-03-08 13:36:44 ) (UTC time)

Note

If the date was not found in the header of the file, an empty string is returned

Public Static Functions

void reset_max_loop_length()

Resets the loop length to zero.

class Metavision::FlipXAlgorithm

Class that allows to mirror the X axis of an event stream.

The transfer function of this filter impacts only the X coordinates of the Event2d by :

$x = width_minus_one - x$

Public Functions

FlipXAlgorithm(std::int16_t width_minus_one)

Builds a new FlipXAlgorithm object with the given width.

Parameters
• width_minus_one: Maximum X coordinate of the events (width-1)

~FlipXAlgorithm() = default

Default destructor.

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

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

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

void operator()(Event2d &ev) const

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

Parameters
• ev: Event2d to be updated

class Metavision::FlipYAlgorithm

Class that allows to mirror the Y axis of an event stream.

The transfer function of this filter impacts only the Y coordinates of the Event2d by :

$y = height_minus_one - y$

Public Functions

FlipYAlgorithm(std::int16_t height_minus_one)

Builds a new FlipYAlgorithm object with the given height.

Parameters
• height_minus_one: Maximum Y coordinate of the events

~FlipYAlgorithm() = default

Default destructor.

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

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

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 height_minus_one() const

Returns the maximum Y coordinate of the events.

Return

Maximum Y coordinate of the events

void set_height_minus_one(std::int16_t height_minus_one)

Sets the maximum Y coordinate of the events.

Parameters
• height_minus_one: Maximum Y coordinate of the events

void operator()(Event2d &ev) const

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

Parameters
• ev: Event2d to be updated

class Metavision::FrameGenerationAlgorithm : private Metavision::AsyncAlgorithm<FrameGenerationAlgorithm>

Class that generates frames from events.

#include <iostream>

#include "metavision/sdk/base/events/event_cd.h"
#include "metavision/sdk/core/algorithms/frame_generation_algorithm.h"

using namespace Metavision;

int main(void) {
// Initializes a frame generation algorithm that generates frames of size 5x1 every 5000 microseconds of events.
// Each frame accumulating the last 10 milliseconds.
FrameGenerationAlgorithm frame_generation(5, 1, 10000, true, 200);

// Sets a callback to print the frame's pixels each time one is generated.
frame_generation.set_output_callback([](const timestamp ts, cv::Mat &frame) {
std::cout << ">> Frame generated at timestamp t = " << ts << " microseconds." << std::endl;
for (int i = 0; i < frame.rows; ++i) {
for (int j = 0; j < frame.cols; ++j) {
std::cout << "(" << j << "," << i << ") = " << frame.at<cv::Vec3b>(i, j) << std::endl;
}
}
std::cout << std::endl;
});
std::vector<EventCD> stream_of_events;

// Given the following events:
// - x = 0, y = 0, p = 1, t = 0
// - x = 1, y = 0, p = 0, t = 4000
// - x = 2, y = 0, p = 1, t = 6000
// - x = 3, y = 0, p = 1, t = 7000
// - x = 4, y = 0, p = 0, t = 13000
stream_of_events.push_back({0, 0, 1, 0});
stream_of_events.push_back({1, 0, 0, 4000});
stream_of_events.push_back({2, 0, 1, 6000});
stream_of_events.push_back({3, 0, 1, 7000});
stream_of_events.push_back({4, 0, 0, 13000});

std::cout << "[First call to 'process_events'] 2 events to process." << std::endl;
frame_generation.process_events(stream_of_events.cbegin(), stream_of_events.cbegin() + 2);
std::cout << "[Second call to 'process_events'] 3 events to process." << std::endl;
frame_generation.process_events(stream_of_events.cbegin() + 2, stream_of_events.cend());
std::cout << "[All events processed. Flushing...]" << std::endl;

// Flush the event pending for asynchronous processing as no event will occur anymore.
frame_generation.flush();
std::cout << "[Done]" << std::endl;

// Output:
//
// [First call to 'process_events'] 2 events to process.
// [Second call to 'process_events'] 3 events to process.
// >> Frame generated at timestamp t = 5000 microseconds.
// (0,0) = [236, 223, 216] # An 'on' event with timestamp 0 occurred in the time range [5000 - 10000; 5000[ -> 'on_color'
// (1,0) = [201, 126, 64] # An 'off' event with timestamp 4000 occurred in the time range [5000 - 10000; 5000[ -> 'off_color'
// (2,0) = [52, 37, 30] # No event occurred in the time range [5000 - 10000; 5000[ -> 'bg_color'
// (3,0) = [52, 37, 30] # No event occurred in the time range [5000 - 10000; 5000[ -> 'bg_color'
// (4,0) = [52, 37, 30] # No event occurred in the time range [5000 - 10000; 5000[ -> 'bg_color'
//
// >> Frame generated at timestamp t = 10000 microseconds.
// (0,0) = [236, 223, 216] # An 'on' event with timestamp 0 occurred in the time range [10000 - 10000; 10000[ -> 'on_color'
// (1,0) = [201, 126, 64]  # An 'off' event with timestamp 4000 occurred in the time range [10000 - 10000; 10000[ -> 'off_color'
// (2,0) = [236, 223, 216] # An 'on' event with timestamp 6000 occurred in the time range [10000 - 10000; 10000[ -> 'on_color'
// (3,0) = [236, 223, 216] # An 'on' event with timestamp 7000 occurred in the time range [10000 - 10000; 10000[ -> 'on_color'
// (4,0) = [52, 37, 30] # No event occurred in the time range [10000 - 10000; 10000[ -> 'bg_color'
//
// [All events processed. Flushing...]
// >> Frame generated at timestamp t = 15000 microseconds.
// (0,0) = [52, 37, 30] # No event occurred in the time range [15000 - 10000; 10000[ -> 'bg_color'
// (1,0) = [52, 37, 30] # No event occurred in the time range [15000 - 10000; 10000[ -> 'bg_color'
// (2,0) = [236, 223, 216] # An 'on' event with timestamp 6000 occurred in the time range [15000 - 10000; 15000[ -> 'on_color'
// (3,0) = [236, 223, 216] # An 'on' event with timestamp 7000 occurred in the time range [15000 - 10000; 15000[ -> 'on_color'
// (4,0) = [201, 126, 64]  # An 'off' event with timestamp 13000 occurred in the time range [15000 - 10000; 15000[ -> 'off_color'
//
// [Done]
}


Public Functions

FrameGenerationAlgorithm(int sensor_width, int sensor_height, timestamp accumulation_time_us, bool colored = true, double fps = 0.)

Constructor.

Parameters
• sensor_width: Sensor’s width (in pixels)

• sensor_height: Sensor’s height (in pixels)

• accumulation_time_us: Accumulation time (in us)

• colored: Generates either colored or grayscale image

• fps: The fps at which to generate the frames. The time reference used is the one from the input events

Exceptions
• std::invalid_argument: If the input fps is not positive or if the input accumulation time is not strictly positive

void set_output_callback(const OutputCb &output_cb)

Function to pass a callback to know when an image has been generated.

Warning

For efficiency purpose, the cv::Mat passed in the callback is the reference to the internal cv::Mat filled. If it is to be used outside the scope of the callback, the user must ensure to swap or copy it to another object.

template<typename InputIt>
void process_events(InputIt it_begin, InputIt it_end)

Function that is calling process online and process state when necessary.

Parameters
• it_begin: First iterator of the buffer

• it_end: End iterator of the buffer

template<typename InputIt>
void process_events(const timestamp ts, InputIt it_begin, InputIt it_end)

Function that is calling process online and process state when necessary.

Parameters
• ts: End timestamp of the buffer. Used if higher than the timestamp of the last event

• it_begin: First iterator of the buffer

• it_end: End iterator of the buffer

void flush()

Function to call process_async and update the internal state of the processing policy accordingly.

void set_fps(double fps)

Sets the fps at which to generate frames and thus the frequency of the asynchronous calls.

The time reference used is the one from the input events.

Parameters
• fps: The fps to use.

Exceptions
• std::invalid_argument: If the input fps is not strictly positive.

double get_fps()

Returns the current fps at which frames are generated.

void set_accumulation_time_us(timestamp accumulation_time_us)

Sets the accumulation time (in us) use to generate a frame.

The accumulation time represents the time range of events to fill the frame with. All events displayed in the generated frame at time t will have occurred in [t - dt, t[, where dt is the accumulation time.

timestamp get_accumulation_time_us()

Returns the current accumulation time (in us).

template<class EventType>
class Metavision::GenericProducerAlgorithm

Allows insertion and storage of events from any source via register_new_event_buffer.

The events will then be produced in a chronological manner with process.

A maximum duration defined by the difference of timestamps between first and last stored event can be set to limit the number of events stored. To enforce this constraint, the producer will either wait for events to be consumed or drop enough events to be able to insert new events, set_max_duration_stored and set_allow_drop_when_overfilled.

Conversely, a timeout can be set, to avoid the producer waiting indefinitely for events to be inserted. According to the timeout value, the producer will either not wait, wait indefinitely or wait for a predefined amount of time before returning the events,

See

set_timeout.

Public Functions

GenericProducerAlgorithm(timestamp timeout = 0, uint32_t max_events_per_second = 0, timestamp max_duration_stored = std::numeric_limits<timestamp>::max(), bool allow_drop_when_overfilled = false)

Constructor.

Parameters
• timeout: Maximum time to wait for events (in us). If equal 0, no timeout is set (equivalent to infinite timeout); if negative, there will be no wait at all.

• max_events_per_second: Maximum event rate when “processing” events up to some time, the latest k events will be output, where k is max_events_per_second * (req_ts - last_ts), the preceding events will simply be dropped

• max_duration_stored: Maximum time difference (in us) between first and last event stored by the producer if the producer already stores enough events, when new events must be added, the oldest events will be dropped if @ref allow_drop_when_overfilled is true, otherwise the producer will wait for enough events to be consumed before continuing

• allow_drop_when_overfilled: If true, the oldest events (i.e. event for which the timestamp if older than latest.t - max_duration_stored) are dropped, otherwise, the producer blocks until the oldest events are consumed

template<typename IteratorEv>
void register_new_event_buffer(IteratorEv start, IteratorEv end)

method to add a new buffer of events

When inserting events, a maximum duration stored by the producer can be set. It is disabled by default, so that the producer storage may grow indefinitely if no events are produced, or the production is too slow. If a maximum duration is set, the producer will never store events such that the difference between the first and last event stored is greater than the maximum duration. To achieve this effect, it will either wait for events to be produced if drop is disabled when the producer has overfilled set_allow_drop_when_overfilled, or it will drop enough events so that this condition is met if drop is enabled.

template<class OutputIt, typename TimingProfilerType = TimingProfiler<false>>
void process(timestamp ts, OutputIt inserter, TimingProfilerType *timing_profiler = TimingProfilerType::instance())

method to produce events up to some timestamp

If the timeout has a positive value, it will wait at most timeout us before returning the events “generated”. If the timeout has a negative value, it will immediately return the events generated. If the timeout is zero, it will wait until at least one event with a timestamp greater than ts is registered, before returning the events with a timestamp less or equal to ts.

Parameters
• ts: Timestamp before which to include events.

• inserter: Iterator to insert the events

• timing_profiler: Profiler to debug

void set_source_as_done()

Sets source as done to let the producer know that no new events will be received.

class Metavision::PolarityFilterAlgorithm

Class filter that only propagates events of a certain polarity.

Public Functions

PolarityFilterAlgorithm(std::int16_t polarity)

Creates a PolarityFilterAlgorithm class with the given polarity.

Parameters
• polarity: Polarity to keep

~PolarityFilterAlgorithm() = default

Default destructor.

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

Applies the Polarity 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 &ev) const

Basic operator to check if an event is accepted.

Parameters
• ev: Event2D to be tested

void set_polarity(std::int16_t polarity)

Sets the polarity of the filter.

Parameters
• polarity: Polarity to be used in the filtering process

std::int16_t polarity() const

Returns the polarity used to filter the events.

Return

Current polarity used in the filtering process

class Metavision::PolarityInverterAlgorithm

Class that implements a Polarity Inverter filter.

The filter changes the polarity of all the filtered events.

Public Functions

PolarityInverterAlgorithm() = default

Builds a new PolarityInverterAlgorithm object.

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

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

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

Changes the polarity of an events.

Parameters
• ev: Event2D that want to be changed

class Metavision::RoiFilterAlgorithm

Class that only propagates events which are contained in a certain window of interest defined by the coordinates of the upper left corner and the lower right corner.

Public Functions

RoiFilterAlgorithm(std::int32_t x0, std::int32_t y0, std::int32_t x1, std::int32_t y1, bool reset_ori)

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

Parameters
• x0: X coordinate of the upper left corner of the ROI window

• y0: Y coordinate of the upper left corner of the ROI window

• x1: X coordinate of the lower right corner of the ROI window s

• y1: Y coordinate of the lower right corner of the ROI window

• reset_ori: If true, events that passed the ROI filter are expressed in the whole image coordinates. If false, they are expressed in the ROI coordinates system

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: Iterator at the beginning of the range of the input elements

• last: Iterator at the end of the range of the input elements

• d_first: Beginning of the destination range

bool is_resetting() const

Returns true if the algorithm is resetting the filtered events.

Return

true if the algorithm is resetting the filtered events

std::int32_t x0() const

Returns the x coordinate of the upper left corner of the ROI window.

Return

X coordinate of the upper left corner

std::int32_t y0() const

Returns the y coordinate of the upper left corner of the ROI window.

Return

Y coordinate of the upper left corner

std::int32_t x1() const

Returns the x coordinate of the lower right corner of the ROI window.

Return

X coordinate of the lower right corner

std::int32_t y1() const

Returns the y coordinate of the lower right corner of the ROI window.

Return

Y coordinate of the lower right corner

void set_x0(std::int32_t x0)

Sets the x coordinate of the upper left corner of the ROW window.

Parameters
• x0: X coordinate of the upper left corner

void set_y0(std::int32_t y0)

Sets the y coordinate of the upper left corner of the ROW window.

Parameters
• y0: Y coordinate of the upper left corner

void set_x1(std::int32_t x1)

Sets the x coordinate of the lower right corner of the ROW window.

Parameters
• x1: X coordinate of the lower right corner

void set_y1(std::int32_t y1)

Sets the x coordinate of the lower right corner of the ROW window.

Parameters
• y1: Y coordinate of the lower right corner

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

Operator applied when reset_ori is true, and the event is accepted.

Parameters
• ev: Event to be updated

template<typename T>
void operator()(T &ev) const

Operator applied when reset_ori == true, and the event is accepted.

Parameters
• ev: Event to be updated

template<typename EventT, bool BOUNDED_MEMORY = true>
class Metavision::SharedEventsBufferProducerAlgorithm : public Metavision::AsyncAlgorithm<SharedEventsBufferProducerAlgorithm<EventT, true>>

A utility class to generate shared ptr around a vector of events according to a processing policy (e.g. AsyncAlgorithm::Processing from AsyncAlgorithm)

The events buffers are allocated within a bounded memory pool (BoundedSharedObjectPool) to reuse the memory and avoid memory allocation.

Template Parameters
• EventT: The type of events contained in the buffer.

• BOUNDED_MEMORY: The type of memory pool to use in the implementation, bounded being a blocking memory pool when all buffers allocated are in use (ObjectPool).

Public Types

using EventsBufferPool = ObjectPool<EventsBuffer, true, BOUNDED_MEMORY>

ObjectPool. We use a bounded one to avoid reallocation

using SharedEventsBufferProducedCb = std::function<void(timestamp, const SharedEventsBuffer&)>

Alias of callback to process a generated SharedEventsBuffer

Public Functions

SharedEventsBufferProducerAlgorithm(SharedEventsBufferProducerParameters params, SharedEventsBufferProducedCb buffer_produced_cb)

Constructor.

Supported mode from (e.g. AsyncAlgorithm::Processing from AsyncAlgorithm): N_EVENTS, N_US, MIXED, NONE.

Setting SharedEventsBufferProducerParameters::buffers_events_count_ to 0 calls set_processing_n_us (unless buffers_time_slice_us_ is 0 as well).

Setting SharedEventsBufferProducerParameters::buffers_time_slice_us_ to 0 calls set_processing_n_events (unless SharedEventsBufferProducerParameters::buffers_events_count_ is 0 as well).

Setting SharedEventsBufferProducerParameters::buffers_events_count_ and SharedEventsBufferProducerParameters::buffers_time_slice_us_ to 0 calls set_processing_none.

Setting non zero value to both SharedEventsBufferProducerParameters::buffers_events_count_ and SharedEventsBufferProducerParameters::buffers_time_slice_us_ calls set_processing_mixed.

The mode can be overridden after calling the constructor.

Parameters
• params: An SharedEventsBufferProducerParameters object containing the parameters.

• buffer_produced_cb: A callback called (SharedEventsBufferProducedCb) whenever a buffer is created.

void clear()

Resets the internal states of the policy.

class Metavision::StreamLoggerAlgorithm

Logs the stream to a file.

Public Functions

StreamLoggerAlgorithm(const std::string &filename, std::size_t width, std::size_t height)

Builds a new new StreamLogger object with given geometry.

Parameters
• filename: Name of the file to write into. If the file already exists, its previous content will be lost.

• width: Width of the producer

• height: Height of the producer

~StreamLoggerAlgorithm() = default

Default destructor.

void enable(bool state, bool reset_ts = true, std::int32_t split_time_seconds = InvalidTimestamp)

Enables or disables data logging.

Parameters
• state: Flag to enable/disable the logger

• reset_ts: Flag to reset the timestamp, the timestamp used in the last call to update will be considered as timestamp zero

• split_time_seconds: Time in seconds to split the file. By default is disabled: InvalidTimestamp (-1).

Exceptions
• It: will throw an exception if the user tries to reset the timestamp or split the stream while the StreamLogger is enabled and running.

bool is_enable() const

Returns state of data logging.

Return

true if data logging in enabled false otherwise

void change_destination(const std::string &filename, bool reset_ts = true)

Changes the destination file of the logger.

Parameters
• filename: Name of the file to write into.

• reset_ts: If we are currently recording, the timestamp used in the last call to update will be considered as timestamp zero

template<class InputIterator>
void process(InputIterator first, InputIterator last, timestamp ts)

Exports the information in the input buffer into the StreamLogger.

Template Parameters
• InputIterator: Read-Only iterator with Event2d base class

Parameters
• first: Beginning of the input iterator

• last: End of the input iterator

• ts: Input buffer timestamp

void close()

Closes the streaming.