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\input texinfo @c -*- texinfo -*-
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@settitle Video Hook Documentation
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@titlepage
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@sp 7
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@center @titlefont{Video Hook Documentation}
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@sp 3
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@end titlepage
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@chapter Introduction
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The video hook functionality is designed (mostly) for live video. It allows
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the video to be modified or examined between the decoder and the encoder.
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Any number of hook modules can be placed inline, and they are run in the
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order that they were specified on the ffmpeg command line.
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Three modules are provided and are described below. They are all intended to
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be used as a base for your own modules. 
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Modules are loaded using the -vhook option to ffmpeg. The value of this parameter
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is a space seperated list of arguments. The first is the module name, and the rest
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are passed as arguments to the Configure function of the module.
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@section null.c
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This does nothing. Actually it converts the input image to RGB24 and then converts
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it back again. This is meant as a sample that you can use to test your setup.
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@section fish.c
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This implements a 'fish detector'. Essentially it converts the image into HSV
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space and tests whether more than a certain percentage of the pixels fall into
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a specific HSV cuboid. If so, then the image is saved into a file for processing
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by other bits of code.
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Why use HSV? It turns out that HSV cuboids represent a more compact range of
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colors than would an RGB cuboid.
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@section imlib2.c
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This allows a caption to be placed onto each frame. It supports inserting the
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time and date. By using the imlib functions, it would be easy to add your own
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graphical logo, add a frame/border, etc.
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@bye