found solution by searching 
the solution is:
--------------------------
Code:
db yum_repositories delete dag
db yum_repositories delete dries
Code:
/sbin/e-smith/db yum_repositories set rpmforge repository \
BaseURL http://apt.sw.be/redhat/el4/en/$basearch/dag \
MirrorList http://apt.sw.be/redhat/el4/en/mirrors-rpmforge \
EnableGroups 1 \
GPGCheck 0 \
Name rpmforge \
Visible yes \
status disabled
Code:
expand-template /etc/yum.conf
Code:
yum --enablerepo=* --disablerepo=smedev install ffmpeg
DO NOT DO THAT seriously that might harm your SME Server. Please only use the configuration for ATrpms, Dries and Dag from the wiki as they are certain to exclude packages that should not be upgraded from their as they have some modifications for SME Server.
You should never instruct users to enable all repositories, you should instruct them to use the minimal set required as bad things may happen. You should, in that case, also have no need to disable the smedev repository as it should never be enabled by default.
I seriously suggest you check your information before posting such dangerous information to the forums even without a proper warning.Never use fedora RPMs on your SME Server, they do (not always) have the same architecture. Your best bet is to see if the package is in ATrpms, Dries or Dag for RHEL4 or CentOS 4, if available there but not in the proper format request a build for RHEL4/Centos4.
On my test server I was able to install ffmpeg using only the ATrpms repository, which I configured according to the wiki:
yum install ffmpeg --enablerepo=aterpms
If you want to install php-ffmpeg you have bad luck as to my knowledge rpm.pbone.net does not list any for RHEL4/Centos4, the ones for fedira are build by an source which is not known to me, and I consider untrusted in cpmparison to Dag, Dries and ATrpms.