Difference between revisions of "Tutorial Videos and Webcams"

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BoofCV focuses on image processing and computer vision algorithms and for the most part relies on other libraries for input and output.  For example, BoofCV does not define GUI widgets but uses Swing instead.  The same philosophy applies to capturing images from videos and webcams.  Unfortunately the built in support in Java for reading videos and webcams is very limited.
BoofCV focuses on image processing and computer vision algorithms and for the most part relies on other libraries for input and output.  For example, BoofCV does not define GUI widgets but uses Swing instead.  The same philosophy applies to capturing images from videos and webcams.  Unfortunately the built in support in Java for reading videos and webcams is very limited. Fortunately there are several 3rd party libraries that do provide support for reading in videos and webcams!


The only video format which BoofCV natively supports is MJPEG and image sequence.  MJPEG is a very simple video format that is for the most part a series of JPEG images concatenated together.  MJPEG's inclusion in BoofCV was primarily to provide video support in applets.  Support is also provided for reading image sequences from directories.
= Reading Videos =
This section describes different approaches that can be used to read in video files.


Third party libraries are required for webcams and reading video formats.  Support for these third party libraries can be found in the 'boofcv/integration' directory.  Of most interest to people are the wrappers for [https://github.com/lessthanoptimal/BoofCV/tree/master/integration/javacv JavaCV] and [https://github.com/lessthanoptimal/BoofCV/tree/master/integration/WebcamCapture Webcam Capture].  JavaCV provides a wrapper around [https://ffmpeg.org/ FFMPEG].  Webcam Capture wraps several different webcam libraries into a simple interface, see their [http://webcam-capture.sarxos.pl/ website] for details.
== Loading Image Files ==


== Converting to MJPEG ==
The most straight forward way to read video is to convert it into an image sequence.  How you do that is dependent on what OS your using and is left as an exercise for the reader.  Typically the way images are handled on the desktop is to first read them in as a BufferedImage and then convert that image into a BoofCV image format.  Here's an example for where a sequence of images is loaded from a directory.
 
<syntaxhighlight lang="java">
List<BufferedImage> images = UtilImageIO.loadImages("path/to/images","jpg");
GrayU8 gray = new GrayU8(1,1);
for( BufferedImage image : images ) {
    ConvertBufferedImage.convertFrom(image,gray,true);
}
</syntaxhighlight>
 
Individual images are also loaded easily using UtilImageIO.
 
 
== Reading MJPEG ==
 
The only video format which BoofCV natively supports is MJPEG and image sequence.  MJPEG is a very simple video format that is for the most part a series of JPEG images concatenated together.  MJPEG's inclusion in BoofCV was primarily to provide video support in Applets.


To read a video and not mess with third party libraries the easiest way to do so is convert the video to MJPEG.  The easiest way in Linux to create an MJPEG from some other video format is using ffmpeg.  Below is a command line example.   
To read a video and not mess with third party libraries the easiest way to do so is convert the video to MJPEG.  The easiest way in Linux to create an MJPEG from some other video format is using ffmpeg.  Below is a command line example.   
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Other flags can be added to resize the image or adjust image quality.  There are a few videos where ffmpeg will produce an MJPEG which BoofCV cannot read, but this is not common.
Other flags can be added to resize the image or adjust image quality.  There are a few videos where ffmpeg will produce an MJPEG which BoofCV cannot read, but this is not common.


== Video ==
== Other Video Formats ==
The easiest way to use Video in BoofCV is to use the default media manager.  It checks your class path to see what you have installed and will use the best option available.  SimpleImageSequence is an interface that provides an easy to use and common interface for different image streams.
The easiest way to use Video in BoofCV is to use the default MediaManager.  It checks your class path to see what you have installed and will use the best option available.  SimpleImageSequence is an interface that provides an easy to use and common interface for different image streams.  Make sure you add the BoofCV module [https://github.com/lessthanoptimal/BoofCV/tree/master/integration/javacv JavaCV] to your project!  JavaCV provides a wrapper around [https://ffmpeg.org/ FFMPEG].  If you don't include this package you will be stuck with just MJPEG files.


<pre>
<pre>
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</pre>
</pre>


The following is a list of alternatives:
The following is a list of alternatives.  Note that a built in MediaManager is not provided for these options.
* Xuggler used supported but after a long protracted death is no longer available
* Xuggler used supported but after a long protracted death is no longer available
* Java Media Framework (JMF)
* Java Media Framework (JMF)
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** Provided by Oracle and supports a few formats.  Known for being old and poorly supported.
** Provided by Oracle and supports a few formats.  Known for being old and poorly supported.


== Webcams ==
= Webcams =


The recommended way to use webcams with BoofCV is with [http://webcam-capture.sarxos.pl/ Webcam Capture].  Webcam Capture is very easy to use and works out of the box on Linux, Windows, and MacOS.  The BoofCV integration package only provides a single function for opening up a camera at a resolution as close to the one you requested as possible.
The recommended way to use webcams with BoofCV is with [http://webcam-capture.sarxos.pl/ Webcam Capture].  Webcam Capture is very easy to use and works out of the box on Linux, Windows, and MacOS.  The BoofCV integration package only provides a single function for opening up a camera at a resolution as close to the one you requested as possible.  You need to be sure that the BoofCV [https://github.com/lessthanoptimal/BoofCV/tree/master/integration/WebcamCapture WebcamCapture] module is included with your project.


[[Example Webcam Capture|Webcam Capture Example]]
[[Example Webcam Capture|Webcam Capture Example]]


Support is also provided for [http://code.google.com/p/v4l4j/ Video for Linux for Java (V4L4J)], but it is more difficult to use and is Linux only.
Other Options:
* [http://code.google.com/p/v4l4j/ Video for Linux for Java (V4L4J)] used to be supported and can still be used but you will need to write your own code to extract the images.


= Other Options =
= BufferedImage =


The easiest way to integrate a 3rd party library with BoofCV is to read in a frame as a BufferedImage, then convert it into a native BoofCV image format using ConvertBufferedImageAn alternative is to write a wrapper that implements SimpleImageSequence, which is used by several examples.
As previously mentioned BufferedImages can be converted into a BoofCV image.  Thus any library which can read a file into BufferedImages can be used with BoofCV.


= Android =


If you know of some other options please post a message to BoofCV's message board (see sidebar link) letting us know about it!  Especially if you have suggestions for Windows and MacOS.
See [[Android Support]] for how to convert Android images into a BoofCV image.

Revision as of 18:35, 3 January 2017

BoofCV focuses on image processing and computer vision algorithms and for the most part relies on other libraries for input and output. For example, BoofCV does not define GUI widgets but uses Swing instead. The same philosophy applies to capturing images from videos and webcams. Unfortunately the built in support in Java for reading videos and webcams is very limited. Fortunately there are several 3rd party libraries that do provide support for reading in videos and webcams!

Reading Videos

This section describes different approaches that can be used to read in video files.

Loading Image Files

The most straight forward way to read video is to convert it into an image sequence. How you do that is dependent on what OS your using and is left as an exercise for the reader. Typically the way images are handled on the desktop is to first read them in as a BufferedImage and then convert that image into a BoofCV image format. Here's an example for where a sequence of images is loaded from a directory.

List<BufferedImage> images = UtilImageIO.loadImages("path/to/images","jpg");
GrayU8 gray = new GrayU8(1,1);
for( BufferedImage image : images ) {
    ConvertBufferedImage.convertFrom(image,gray,true);
}

Individual images are also loaded easily using UtilImageIO.


Reading MJPEG

The only video format which BoofCV natively supports is MJPEG and image sequence. MJPEG is a very simple video format that is for the most part a series of JPEG images concatenated together. MJPEG's inclusion in BoofCV was primarily to provide video support in Applets.

To read a video and not mess with third party libraries the easiest way to do so is convert the video to MJPEG. The easiest way in Linux to create an MJPEG from some other video format is using ffmpeg. Below is a command line example.

ffmpeg -i FILENAME -sameq example.mjpeg

Other flags can be added to resize the image or adjust image quality. There are a few videos where ffmpeg will produce an MJPEG which BoofCV cannot read, but this is not common.

Other Video Formats

The easiest way to use Video in BoofCV is to use the default MediaManager. It checks your class path to see what you have installed and will use the best option available. SimpleImageSequence is an interface that provides an easy to use and common interface for different image streams. Make sure you add the BoofCV module JavaCV to your project! JavaCV provides a wrapper around FFMPEG. If you don't include this package you will be stuck with just MJPEG files.

MediaManager media = DefaultMediaManager.INSTANCE;
SimpleImageSequence<Planar<GrayU8>> video = media.openVideo(fileName, ImageType.pl(3,GrayU8.class);

while( video.hasNext() ) {
  Planar<GrayU8> input = video.next();
  ... process ...
}

The following is a list of alternatives. Note that a built in MediaManager is not provided for these options.

Webcams

The recommended way to use webcams with BoofCV is with Webcam Capture. Webcam Capture is very easy to use and works out of the box on Linux, Windows, and MacOS. The BoofCV integration package only provides a single function for opening up a camera at a resolution as close to the one you requested as possible. You need to be sure that the BoofCV WebcamCapture module is included with your project.

Webcam Capture Example

Other Options:

BufferedImage

As previously mentioned BufferedImages can be converted into a BoofCV image. Thus any library which can read a file into BufferedImages can be used with BoofCV.

Android

See Android Support for how to convert Android images into a BoofCV image.