Video Stream Framing with Smooth Auto-Zoom Transitions
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Solution Overview
Problem
Existing videoconferencing systems experience abrupt image changes and jerky effects during automatic framing due to constant-speed movement, creating an impression of robotic subject movement.
Innovation Solution
An improved method for selecting and displaying image portions in a video stream by determining the boundaries of a subject, applying temporal filtering, and using a hysteresis mechanism to adjust zoom factors, ensuring smooth transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If automatic framing follows the user with constant-speed movement, then the subject position is tracked accurately, but jerky and shaky effects occur creating robotic movement impression
Solution Approach 1:
The patent applies dynamics by transitioning from constant-speed movement to accelerated movement with variable speed. The framing now accelerates when the subject moves, creating smooth transitions instead of jerky effects. This dynamic approach allows the system to adapt its speed based on subject movement, eliminating the robotic impression while maintaining accurate tracking.
Solution Approach 2:
The patent changes the movement parameter from constant speed to variable speed with acceleration. By introducing acceleration as a new parameter and modifying the speed characteristic, the system achieves smooth framing transitions. This parameter change transforms the harmful constant-speed behavior into a beneficial accelerated movement pattern that eliminates jerky effects.
2Measurement precision
If zoom factors are adjusted frequently to follow subject movement, then subject tracking is maintained, but image stability deteriorates causing visual discomfort
Solution Approach 1:
The patent applies dynamics by implementing accelerated zooming instead of frequent incremental adjustments. The zoom factor now changes with acceleration based on subject movement, maintaining tracking precision while reducing the number of adjustments. This dynamic zooming approach stabilizes the image by avoiding frequent small changes that cause visual discomfort.
Solution Approach 2:
The patent ensures continuity of useful action by using accelerated zooming to maintain subject tracking in a continuous manner. Instead of discrete frequent adjustments, the system performs smooth continuous zooming that maintains tracking while preserving image stability. This continuous action eliminates the destabilizing effect of frequent discrete zoom changes.
3Object-generated harmful factors
If temporal filtering is applied to smooth transitions, then jerky effects are reduced, but response time increases causing lag in subject tracking
Solution Approach 1:
The patent changes the temporal parameter from gradual filtering to accelerated transitions. By applying acceleration to the framing and zooming operations, the system achieves smooth transitions without the lag associated with temporal filtering. The accelerated parameter changes maintain responsiveness while eliminating jerky effects, avoiding the time loss inherent in filtering approaches.
Data Source
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AI summary
The invention relates to a method for selecting portions of images from a video stream comprising a representation of a subject, the method comprising the steps of determining (S1) a first portion of image comprising said subject, of determining (S2) a target zoom factor from a plurality of zoom factors from the determined limits, a current zoom factor and at least a maximum image resolution and of determining (S3) target coordinates of the first portion of image cropped as a function of the determined target zoom factor and a maximum image resolution.