MIPI CSI-2 Event Stream Transmission via Frame Period Assignment

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Solution Overview

Problem

Standard camera interfaces, such as MIPI CSI-2, are not compatible with event-based cameras due to their frame-based design, which is incompatible with the variable and event-driven nature of event streams, leading to issues with interoperability and data transmission efficiency.

Innovation Solution

A method is developed to transmit event streams by assigning a period to frames and packets, filling packets with events within that period, and using padding events to maintain compatibility with standard interfaces, ensuring a fixed frame rate and efficient data transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If standard frame-based camera interfaces (MIPI CSI-2) are used for event stream transmission, then interoperability with existing end devices is achieved, but compatibility issues arise due to the fundamental mismatch between frame-based and event-based data structures

Engineering Contradiction:

ImproveinteroperabilityVSAvoidcompatibility

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an intermediary formatting layer that translates event stream data into frame-based packets. This intermediary structure includes packet headers with event counts, timestamp ranges, and type information, allowing event data to be conveyed through the frame-based MIPI interface without direct compatibility conflicts

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the parameter representation by encoding event data in a structured packet format rather than raw event streams. Each packet contains metadata parameters (event count, timestamp min/max, event types) that transform the variable-rate event data into a fixed-structure format suitable for frame-based transmission

Inventive Principle:

Principle #35Parameter changes

2Productivity

If events are transmitted in variable rate according to occurrence triggers, then data transmission efficiency is improved, but incompatibility with fixed frame structures occurs

Engineering Contradiction:

Improvedata transmission efficiencyVSAvoidinterface compatibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The event stream is segmented into discrete packets, each containing a specific number of events with associated metadata. This segmentation allows the variable-rate event data to be divided into fixed-size transmission units that fit within the frame structure, maintaining both efficiency and compatibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The packet structure dynamically adapts to event rates by varying the number of events per packet while maintaining a fixed overall packet format. The packet count and event distribution adjust dynamically based on event occurrence rates, allowing efficient variable-rate transmission within a static frame framework

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If packets are filled only with triggered events, then transmission bandwidth is optimized, but fixed packet capacity requirements cannot be met

Engineering Contradiction:

Improvebandwidth optimizationVSAvoidpacket capacity consistency

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent applies local quality by using padding events specifically in the last packet of each frame when event data is insufficient to fill the packet capacity. This localized padding approach maintains fixed packet capacity requirements only where necessary, while allowing bandwidth optimization in packets that are fully filled with actual event data

Inventive Principle:

Principle #3Local quality

4Measurement precision

If frame period is assigned to structure event transmission, then timing synchronization is improved, but latency and jitter are introduced due to frame-based structuring

Engineering Contradiction:

Improvetiming synchronizationVSAvoidlatency and jitter

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent uses preliminary action by pre-defining frame periods and packet structures before event transmission begins. Timestamps are recorded and organized into predetermined time windows corresponding to frame periods, allowing events to be sorted and packed efficiently without real-time timing negotiations, thereby reducing latency while maintaining synchronization

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20240422286A1Transmission of an event stream through a MIPI camera serial interface

Publication Date: 2024.12.19 PROPHESEE SOLUTIONS PVT LTD

AI summary

A method for transmitting an event stream produced by an event-based vision sensor over an interface configured to transmit data in successive packets grouped in successive frames comprises the steps of assigning a period to the frames; reading events with respective timestamps from the event stream; and filling packets of a current frame only with events that have a timestamp within the period of the current frame.