[Slackbuilds-users] vlc fails

Christoph Willing chris.willing at linux.com
Mon Feb 19 04:55:04 UTC 2018

On 19/02/18 11:20, B Watson wrote:
> On 2/18/18, Christoph Willing <chris.willing at iinet.net.au> wrote:
>> Since this issue involves three different projects (VTK, opencv, vlc), I
>> don't expect a speedy resolution. I've therefore updated the SlackBuild
>> to disable opencv support. Experimenters can explicitly turn it back on
>> at build time with the OPENCV environment variable e.g.
>>     OPENCV=yes sh vlc.SlackBuild
> For those of us who don't use vlc regularly... what vlc feature(s)
> depend on opencv? From the description, is for "computer vision and
> machine learning". What does vlc use it for, exactly?
OpenCV as well as other "computer vision and machine learning" software
often use video streams as their input. Although OpenCV has its own
video input module, it's easy to imagine that a specialised video tool
like vlc might have greater functionality that make it more attractive
as a video reader than OpenCV's native video reader. The opencv plugin
for vlc enables opencv's video processing tools to be applied directly
within vlc.

The example plugin (the one causing the build problem with the latest
vlc at the moment) is a face recognition filter. A simple non-opencv
filter that gives an idea of how these filters work is the built in
motion detection tool. Test it as follows: play a video and select
Tools->Effects & Filters, then select Video Effects tab in the resulting
window, then the Advanced tab and its Motion detect selector. See moving
parts of video highlighted. Not great for watching movies but useful for
those who find these things useful :)

> Also, I notice there's an older opencv version in the repo, as
> opencv-legacy. Does it work with vlc?
Yes, good point. I'll add that to the README.


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