LinuxQuestions.org - Yum install public key issue, not working for ffmpeg

Hello,
I have a video in AVI format that I want to convert onto a DVD to watch in a household player. I'm following the instructions on this site to convert the AVI to mpeg (http://gentoo-wiki.com/HOWTO_Create_a_VCD_or_SVCD). I do not have ffmpeg on my machine. So, I tried to use yum to make the install and here is what I get....

yum install ffmpeg
Setting up Install Process
Setting up Repos
dag 100% |=========================| 1.1 kB 00:00
base 100% |=========================| 1.1 kB 00:00
updates-released 100% |=========================| 951 B 00:00
Reading repository metadata in from local files
dag : ################################################## 5609/5609
base : ################################################## 2622/2622
updates-re: ################################################## 910/910
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Package ffmpeg.i386 0:0.4.9-0.20041110.3.1.el3.rf set to be updated
--> Running transaction check
--> Processing Dependency: libImlib2.so.1 for package: ffmpeg
--> Processing Dependency: libpostproc.so.0 for package: ffmpeg
--> Processing Dependency: libxvidcore.so.4 for package: ffmpeg
--> Processing Dependency: libfaad.so.0 for package: ffmpeg
--> Processing Dependency: libfaac.so.0 for package: ffmpeg
--> Restarting Dependency Resolution with new changes.
--> Populating transaction set with selected packages. Please wait.
---> Package libpostproc.i386 0:1.0-0.17.pre7.1.el3.rf set to be updated
---> Package faac.i386 0:1.24-1.1.el3.rf set to be updated
---> Package xvidcore.i386 0:1.1.0-3.el3.rf set to be updated
---> Package imlib2.i386 0:1.2.0-1.1.el3.rf set to be updated
---> Package faad2.i386 0:2.0-4.1.el3.rf set to be updated
--> Running transaction check

Dependencies Resolved
Transaction Listing:
Install: ffmpeg.i386 0:0.4.9-0.20041110.3.1.el3.rf - dag

Performing the following to resolve dependencies:
Install: faac.i386 0:1.24-1.1.el3.rf - dag
Install: faad2.i386 0:2.0-4.1.el3.rf - dag
Install: imlib2.i386 0:1.2.0-1.1.el3.rf - dag
Install: libpostproc.i386 0:1.0-0.17.pre7.1.el3.rf - dag
Install: xvidcore.i386 0:1.1.0-3.el3.rf - dag
Total download size: 3.7 M
Is this ok [y/N]: y
Downloading Packages:
warning: rpmts_HdrFromFdno: V3 DSA signature: NOKEY, key ID 6b8d79e6
public key not available for libpostproc-1.0-0.17.pre7.1.el3.rf.i386.rpm

This is all greek to me. What is wrong? I used the download depository that was recommended on this site (http://www.centos.org/modules/newbb/...?topic_id=3660)

Thanks a lot,
~Mark