I install ffmpeg and its dependencies in Slackware 14.0.
when run ffmpeg, i got this error message

so, where can I find those libraries.
my times have already wasted much on it. but I can't.

I don't know about Slackware but in Debian it's found in the libjack-jackd2-0 package. Maybe slackware has something with a similar name.
jdk

Slackware does not provide ffmpeg in its offical repositories. Where have you obtained this package or are you trying t compile from source. If you are using a binary package from someone else they should provide the package with libjack.

Why not use AlienBOB's ffmpeg package or build ffmpeg from the SlackBuild found on SBo?

I used slackbuild.

I could install ffmpeg's dependencies (lame, x264) using sbopkg. but I couldn't install ffmpeg using "sbopkg -i ffmpeg"
it tried again and again many time to download and at the end, sbopkg failed to download and install ffmpeg.

anyway, I downloaded one from this page http://ffmpeg.gusari.org/static/ and extracted simply.
I found ffmpeg and ffprobe. so I copied them to /usr/bin. the previous ones already existed in there were deleted.

now, ffmpeg works, everything ok, my work is a bit dirty though.

anyway, thanks for ur post, I checked the pages u mention and downloaded opera-12.15.
I am going to learn what it is and keep it just in case.

btw, what are those Opera and Opera Next.
those pages say you did them.

@mshlinux: If you have trouble building things from SlackBuilds.org I would suggest posting here in the future with the exact error messages you received, along with any relevant information, such as if you have a full install or not. There are plenty of people here who could help you to get to the root of the problem if you so desire.

Another tip, if you have issues with SlackBuilds.org or would prefer binary packages I strongly recommend that you consider AlienBOB's repository as your next port of call. It has less packages than SlackBuilds.org but it does include many of the most popular ones. AlienBOB is a long time contributor to Slackware and his packages are highly regarded and trusted by the community here on LinuxQuestions. Using his binary Slackware packages is certainly advisable to copying ffmpeg files into various directories on your system outside of official packaging.

With regards to the Opera and Opera Next links. They have nothing to do with my response to you on this particular topic, they are simply part of my standard signature and appear on all my posts. Opera is a web browser (a rival to programs like Firefox, or Internet Explorer on Windows). The 'Next' version is the current publicly available development version, incorporating the latest features and fixes. Though being a development version it is less tested and hence not yet considered stable.

Opera does not provide official Slackware packages. However as I work for Opera Software in the Linux/FreeBSD team and use Slackware myself, I frequently repackage Opera into native Slackware package format for my own use. I then make those packages available for others who might be interested via those links in my signature.