vlc installation on Slackware
 

I tried to install VLC from source but when i unpacked and did command ./configure, this happened:
What should I do?

"postprocess.h" is looking for a header file (a .h file) that appears in "postprocess.h" but not in your Slack installation.

For example "postprocess.h" might refer to a "/usr/src/linux/../../foo.h" but for some reason Slack doesn't have a "foo.h", or it's not where the programmer expected it.

So you need to find the missing header file and put it where the VLC source expects it to be.