EVT 2.0 Encoding Format

EVT 2.0 is a 32-bit data format, and it supports sensors with up to 2048x2048 resolution.

Raw data are stored in 32-bit (4 bytes) words for each event.

The 4 Most Significant Bits (MSB) are used to define the EVT 2.0 word type.

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

Event

Description

Value

CD_OFF

Primary (left) camera CD event, decrease in illumination (polarity ‘0’)

‘0000’

CD_ON

Primary (left) camera CD event, 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.

34 bits timestamp representation

To compute the full resolution of the timestamp, the first event type in the stream is an EVT_TIME_HIGH event.

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.