[blfs-support] gst-plugins-bad-1.0 does not build if opencv is present

Pierre Labastie pierre.labastie at neuf.fr
Thu Dec 22 07:06:50 PST 2016

On 22/12/2016 14:59, Douglas R. Reno wrote:
> On Thu, Dec 22, 2016 at 6:58 AM, Pierre Labastie 
> <pierre.labastie at neuf.fr <mailto:pierre.labastie at neuf.fr>> wrote:
>     Hi,
>     I am amazed that nobody came to that earlier, but if
>     opencv-3.1.0 is installed as per the book instructions,
>     gst-plugins-bad does not build. The error is:
>     ------------------------
>     make[3]: Entering directory
>     '/sources/gst10-plugins-bad/gst-plugins-bad-1.10.2/ext/opencv'
>       CXX      libgstopencv_la-gstopencv.lo
>     In file included from gstopencv.cpp:41:0:
>     gstsegmentation.h:53:32: fatal error: opencv2/bgsegm.hpp: No such
>     file or
>     directory
>        #include <opencv2/bgsegm.hpp>
>                                     ^
>     compilation terminated.
>     make[3]: *** [Makefile:1016: libgstopencv_la-gstopencv.lo] Error 1
>     -----------------------
>     After much research (I'm really not good at finding
>     things on internet, thanks Arch linux), I found that
>     the bgsegm module is from the opencv_contrib
>     package, and not included in the main opencv
>     package (there is a cudabgsegm module in the
>     main pacakge, but not available if not using cuda,
>     that is, nvidia proprietary graphics driver). I have
>     not yet tried to build the opencv_contrib package,
>     nor to build gst-plugins-bad with that package
>     installed. But I wanted to report to see whether
>     anybody could confirm. I'd say that if confirmed,
>     we should add the opencv_contrib package as
>     optional (or disable gstopencv in gst-plugins-bad).
>     Regards,
>     Pierre
>     Regards
> Hi Pierre,
> I generally don't build OpenCV when updating gst-plugins-bad, as most 
> of the time I'm heading towards GNOME and need the gst plugins as 
> dependencies.
> If you want me to confirm, I'll be building through gst-plugins-* in a 
> couple hours, so that I can build WebkitGTK+. I can try building 
> OpenCV this time if you want.
> Otherwise, my two cents is to disable gstopencv, but I can see where 
> adding the contrib package could help. I just don't see too much of a 
> use for OpenCV in gst-plugins-bad currently.
I'd say it would allow to build some image recognition module... Whether 
it is useful (for cheese or whatever), I can't tell.

Problem is: opencv is in the in the optional deps of gst-plugins-bad, so 
users may build it, for whatever reason [*]. In this case 
gst-plugins-base does not build. OTOH, BLFS editors are not supposed to 
test building with optional deps.
So, I might just disable opencv in gstreamer, and add a command 
explanation telling that extra modules are needed if users want to 
enable it.

[*] I've bought a webcam, as advised by you ;-), but cheese is unable to 
access it, so I thought I would rebuild gst-plugins with all deps to 
make sure I have the right ones. The book is not very explicit about 
which deps are needed for which usage...

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