If the extension is ".tar.gz", it's probably not configured to work correctly for VL, even after it's extracted. It's pretty much a guarantee that it's a bad idea to try to install it as if it were a package.
You're asking questions that, in a general way, the forum has tried to address publicly for longer than most of us have been around -- much longer than I have, certainly. Thanks for bringing this up where it can be seen. Just letting you know it might be a long ride.
You're trying to get an updated avidemux package, right? What might work (I'd give it a 40% chance) is to download the complete directory I linked above. Change all references to the old version to the new version. This should mean changing the directory names that include the version number to the new one, and editing avidemux.SlackBuild to the new version, build #1, you're the packager, a good URL for the source, and so on. Also, find and delete the file "slack-depends" (I think the slackbuild contains info to regenerate this, not looking at it right now). Then cd <path-to-files>/avidemux/<version>/src, Become root, and do: sh avidemux.SlackBuild
To be a proper package, the above would have to be built on a clean buildbase and some other minor changes would have to be made. But knowing whether it works on the system you have, or what errors are generated could be a good head start.
The above could be too much for you; it usually is too much for me. In that case, where did you get the .tar.gz file you mentioned?
