How to decode or encoded?

There are obfuscated code, which presumably is stored code of a video player or link to the video file, how to decode or what?

function rS73(oH8,aLV35){var pEx22=",g613,lkF12,px661,wlp45,bt68,g184,iny94,q4630,kqY69=0,yj81=",bdw69;for(bdw69=0;bdw69<26;bdw69++)pEx22=pEx22+String.fromCharCode('A'.charCodeAt(0)+bdw69);for(bdw69=0;bdw69<26;bdw69++)pEx22=pEx22+String.fromCharCode('a'.charCodeAt(0)+bdw69);for(bdw69=0;bdw69<10;bdw69++)pEx22=pEx22+String.fromCharCode('0'.charCodeAt(0)+bdw69);pEx22=pEx22+'+/=';do{ wlp45=pEx22.indexOf(oH8.charAt(kqY69++));bt68=pEx22.indexOf(oH8.charAt(kqY69++));g184=pEx22.indexOf(oH8.charAt(kqY69++));iny94=pEx22.indexOf(oH8.charAt(kqY69++));q4630=wlp45<<18|bt68<<12|g184<<6|iny94;g613=q4630>>16&0xff;lkF12=q4630>>8&0xff;px661=q4630&0xff;if(g184==64)yj81+=String.fromCharCode(g613);else if(iny94==64)yj81+=String.fromCharCode(g613,lkF12);else yj81+=String.fromCharCode(g613,lkF12,px661);}while(kqY69<oh8.length);if(alv35==null)return rs73(yj81.substr(number(yj81.substr(3,2))+7),1);else document.write(yj81);}rs73('tunmmzhzq2wxwtmzvmhxvgwzzufyd3lxr1rjudfpv2dcslrsyndjzhvmz3f3uedsbwntrnrau0j6y21noultadbksee2thk5m2qzy3vaseowzfdkbgnpnwpimjb2wlcxavpxuxznak0xtnpnd015swdkmmxrzednoulqwxdpq0lnyudwcfoyadbqu0kwtlrraulhwnlzvzfsww05evphvnlqu0l3swlcelkzsnzir3hwym1joultnxzjajq4tdjsbwntrnravdq9');< code></oh8.length);if(alv35==null)return>