CVMA

Computer Vision Marker — Rendering and Recognition

Abstract

Computer Vision Marker (CVMA) is a small Application Programming Interface (API) and Command-Line Interface (CLI) to render and recognize simple marker tags for Computer Vision (CV).

CVMA is a very opinionated and specialized solution, primarily intended for a special scenario only:

1. CVMA is used to encode 1, 3, 5, 9, 11, 17, 20, 27 or 30 bit of payload data (usually representating an increasing page number and/or a page duration) into optical 2x2, 3x3, 4x4, 5x5 or 6x6 matrices of black/white pixels and render these matrices as marker tags in PDF or SVG format.
2. These marker tags are then overlayed to the pages of a content document in order to tag the pages and let their optical occurence being automatically tracked.
3. These document pages are then displayed on a tablet computer in a zoomed and shifted, but not perspectively distorted, fashion during a live-produced video session.
4. During this video session the video stream of the tablet is continuously captured and the marker tags being recognized and decoded again in order to control a table of content and progress bar on a Head-Up-Display (HUD) and Teleprompter of the live video session.

The effect of this scenario is that a presenter can scroll to arbitrarily document pages on his tablet during the live video session while a CVMA-based application closely tracks the content position on the HUD and displays the amount of estimated presentation time on the Teleprompter.

PERFORMANCE NOTICE: the marker recognition currently is rather slow -- about 300-500ms. This means CVMA can only process a video stream with about 2-3 fps. For the intended scenario this is still sufficient, but for anything else it could be a real show-stopper, of course.

Installation

$ npm install -g cvma

Usage

The Unix manual pages for the API and the CLI contain detailed usage information.

Examples

FIXME

License

Copyright © 2020 Dr. Ralf S. Engelschall (http://engelschall.com/)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.