$ sudo apt-get update
$ sudo apt-get install libavcodec53 

libavcodec53 is installed in your system.

Make ensure the libavcodec53 package were installed using the commands given below,

$ sudo dpkg-query -l | grep libavcodec53 *

You will get with libavcodec53 package name, version, architecture and description in a table

libavcodec53 package basic information: