Some time ago, I bumped into a dead end when trying to implement the face-tracking overlays feature. The problem started when I tried to set the overlay width and height in run time.
The opencv facedetect gst-plugin sends bus messages with the x, y, width and height of the faces it detects. I captured the messages and set the rsvgoverlay element x and y properties without problems. But rsvgoverlay element lacks width and height properties.
This meant that if you moved your face away or close from the camera, the mask would still look the same size, or if the svg dimensions were huge or tiny, it would look that way instead of resizing to the face size.
I contacted rsvgoverlay maintainer Olivier Aubert to see if width and height could be added as properties for that element. He preferred not to and explained to me the reasons. (He pointed me to
this bug where coincidentally
Luciana had asked for something similar before our internships in GNOME Outreach program started, and she
implemented a plugin for png overlays already, I haven't checked it yet).
Well, Olivier suggested I used the SVG data itself to set size and position. So I started implementing this:
Then I realized: for this to work, I needed the SVG file path and we don't have a way to know it on runtime right now. It is parsed as part of the pipeline description from the .effect files in gnome-video-effects and the entire pipeline description is used to create the rsvgoverlay element. The same applies to all other effects. So to access that path, we would have to start knowing which effect we are handling at a specific time inside of cheese, and we don't want to do that.
Other option would be to parse the .effect files in a different way. That's something that is already being discussed
here and it will allow for more functionality than I need for this.
So I started writing my very own GStreamer plugin, to have more control and manage several options and use cases better. Maybe I'll be using the existing rsvgoverlay and facedetect plugins somehow.
Last days I was following the steps in
GStreamer Plugin Writer's Guide and climbing the vertical autotools learning curve. Hoo boy.
About Autotools:
Task #1: add a subdirectory named "pixmaps" with .svg images to gnome-video-effects to be installed in /usr/share/gnome-video-effects/pixmaps when running make install.
The files to edit were: gnome-video-effects/configure.ac and gnome-video-effects/Makefile.am
And a new Makefile.am needs to be added in the new pixmaps directory:
It looks simple now, but finding out how to do this, from which files to edit to what to add there, was a guessing-in-the-dark ordeal.
Task #2: include <cv.h> in my new plugin header file. Run "make" without errors.
Holy tap-dancing christ with crutches. This is so easy to do in Visual Studio. Just add the include path and the library to link against. But what to say about autotools that hasn't been said already? (With this I'm not saying that everything about programming in Windows is better, absolutely on the contrary: programming in linux is paradise compared to that. But creating a new little project to tinker and test things quickly? Yes, that is lacking in linux that I know of).
Files that needed to be edited: configure.ac in top-level directory, and Makefikle.am in src directory.
Here I include the entire Makefile.am file with added parts in blue:
Such a simple starter Makefile.am with instructions, such a small change to add. But to discover what had to be changed!
And to configure.ac I added:
And I don't even know if this last one is really ok because I placed the AC_SUBST macros inside an if and I don't know if that's valid. All this was made copying from already working projects with similar stuff and changing things until it worked, 9879864 "./autogen.sh &&./configure && make && make install" attempts later.
A programmer in fierce battle against GNU Autotools
How is it possible...? That it's so difficult? I cannot believe it. I felt that I needed to change a lightbulb; the documentation explained the history of electricity, the reference was as big as a manual to build your own nuclear reactor, and the examples explained how to light a candle.
Just this minute I found this:
http://smalltalk.gnu.org/blog/bonzinip/all-you-should-really-know-about-autoconf-and-automake
I had to google "GNU Autotools hate" to find it.
And there is a lot more I'd like to say about autotools! But I'll let that for a RANT&RAGE type post, if I ever get to write about it ;)
