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Learn OpenCV 4 by Building Projects - Second Edition by Prateek Joshi, Vinicius G. Mendonca, David Millan Escriva

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Reading videos and cameras

This section introduces you to video and camera reading using this simple example. Before explaining how to read videos or camera input, we want to introduce a new, very useful class that helps us to manage the input command-line parameters. This new class was introduced in OpenCV version 3.0, and is the CommandLineParser class:

// OpenCV command line parser functions 
// Keys accepted by command line parser 
const char* keys = 
{ 
   "{help h usage ? | | print this message}" 
    "{@video | | Video file, if not defined try to use webcamera}" 
}; 

The first thing that we have to do for CommandLineParser is define what parameters we need or allow in a constant char vector; each line has the following pattern:

"{name_param | default_value ...

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