ffmpeg unmet dependencies

I'd think you've used this ppa, possibly to install vlc, which installed libavcodec-extra-53 4:0.8.0.1~ppa2 - https://launchpad.net/~n-muench/+archive/vlc

(typically when you see an error like "but blah-blah is to be installed", what that means is 'blah-blah' is already installed

If the ppa is still enabled, (doubtful), then run sudo apt-get update

If it's not currently enabled then re-enable or add back, then run above command & you'll be able to install ffmpeg or libav-tools which provides avconv

avconv will be the preferred way to run 'ffmpeg' as sooner or later the ffmpeg binary will no longer be provided in Debian/Ubuntu

If you decide that using backported ffmpeg shared libs isn't what you want then after enabling the ppa run ppa-purge as suggested. (The ppa isn't proving all packages that depend on the shared ffmpeg libs so some apps or plugins could have issues

I tried steps given in following link and it works :)

http://ubuntuforums.org/showpost.php?p=5962046&postcount=9

Try

sudo apt-get update

to update your package list. Then

sudo apt-get autoclean

to clean up any partial packages. Then

sudo apt-get clean

to clean up the apt cache.

sudo apt-get autoremove

will clean up any unneeded dependencies.

If while doing this you can identify the broken package this code will very forcefully remove it.

sudo dpkg --remove -force --force-remove-reinstreq <package name>

Change package name to the real name of course.