Fede,
here you are the commands I used:
$ ./autogen.sh
$ ./configure --with-pd=/Applications/Pd-0.49-1.app/Contents/Resources --enable-videoAVF --with-libvlc-CFLAGS=-I/Applications/VLC.app/Contents/MacOS/include --with-libvlc-LIBS='-L/Applications/VLC.app/Contents/MacOS/lib -lvlc' --without-Carbon-framework --with-defaultwindow=gemcocoawindow --without-ftgl --without-imagemagick GL_CFLAGS="-DDUMMY_GL" GL_LIBS="-framework OpenGL"
$ make
$ make install
feel free to delete those elements what you need, I had to cancel ftgl or imagemmagick as looks like in Mojave for some reason cmake symlinks does not work properly, and those elements which I updated with brew or macport or compiled with cmake just cannot be found by Gem.
Anyway, please let us all know if you can compile and have pix_video make working properly.
Best,
Popesz