EVT 2.0 Format

EVT 2.0 is a 32-bit data format supporting sensors with up to 2048x2048 resolution. It is a very robust format that does not contain any vectorization (contrary to EVT 3.0) and is destined for low event rate applications.

The data transmission follows either little or big-endian format, which is determined by the sensor configuration. By default, IMX636 and GenX320 sensors transmit data in little-endian format, where the least significant byte comes first and the most significant one comes last.

In each 32-bit EVT 2.0 word, the 4 Most Significant Bits (MSB) are used to define the word type.

The following table depicts the different types of events data that can be encountered:

Event	Description	Value
CD_OFF	OFF CD event, i.e. decrease in illumination (polarity ‘0’)	‘0000’
CD_ON	ON CD event, i.e. increase in illumination (polarity ‘1’)	‘0001’
EVT_TIME_HIGH	Timer high bits: MSB part of the events timestamp. Least Significant Bits (LSB) are attached to CD_OFF / CD_ON words.	‘1000’
EXT_TRIGGER	External trigger output	‘1010’
OTHERS	To be used for extensions in the event types	‘1110’
CONTINUED	Extra data that are used for the events which arrive in several words. Vendor specific, contact your event-based camera distributor.	‘1111’

Note

Other event types are reserved. Contact your event-based camera distributor if you receive EVT 2.0 words whose type is not described in this table.

Event Time Encoding

All events are timestamped with a micro-second precision. Timestamp are encoded with 34 bits, providing a rollout after: 2³⁴ μs = 4 hours and 46 minutes. In order to minimize the amount of information stored with each event, the event timestamp is encoded in two parts. Lower 6 significant bits (0..5) of the micro-second timestamp are directly encoded into the CD or Trigger event, while the 28 most significant bits (6..33) of the timestamp are stored in a dedicated EVT_TIME_HIGH event. To rebuild the full event timestamp, the lower bits of the timestamp embedded in the event must be concatenated with the last EVT_TIME_HIGH event information.

To compute the full resolution of the timestamp, decoding of the event stream should start after receiving the first event of type EVT_TIME_HIGH.

CD_OFF

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | CD_OFF (‘0000’)	(‘0000’)
27..22	6 bits	timestamp	Least significant bits of the event time base	–
21..11	11 bits	x	Pixel X coordinate	–
10..0	11 bits	y	Pixel Y coordinate	–

Note

Polarity of CD_OFF events is implicitly 0, encoding a decrease of illumination.

CD_ON

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | CD_ON (‘0001’)	(‘0001’)
27..22	6 bits	timestamp	Least significant bits of the event time base	–
21..11	11 bits	x	Pixel X coordinate	–
10..0	11 bits	y	Pixel Y coordinate	–

Note

Polarity of CD_ON events is implicitly 1, encoding an increase of illumination.

EVT_TIME_HIGH

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | EVT_TIME_HIGH	(‘1000’)
27..0	28 bits	timestamp	Most significant bits of the event time base (33..6)	–

EXT_TRIGGER

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | EXT_TRIGGER	(‘1010’)
27..22	6 bits	timestamp	Least significant bits of the event time base	–
21..13	9 bits	–	Unused	–
12..8	5 bits	id	Trigger channel ID	–
7..1	7 bits	–	Unused	–
0	1 bit	value	Trigger current value (edge polarity): 0: falling edge 1: rising edge	‘0’

Note

Trigger Channel ID may vary from one event-based Camera to another. Contact your event-based Camera vendor to get more information on this value.

OTHERS

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | OTHERS	(‘1110’)
27..22	6 bits	timestamp	Least significant bits of the event time base	–
21..17	5 bits	–	Unused	–
16	bit	class	Event class: 0: Monitoring 1: TBD	–
15..0	16 bits	subtype	Event sub-type	–

Note

OTHERS EVT 2.0 words are vendor specific. Contact your event-based camera vendor to get more details.

CONTINUED

Bit Range	Bit Width	Field Name	Description	Default Value
31..28	4 bits	type	Event type | CONTINUED	(‘1111’)
27..0	28 bits	–	Depends on the previous event	–

Note

CONTINUED EVT 2.0 words are vendor specific. Contact your event-based camera vendor to get more details.