how to convert one media file to another (i.e. jpeg to Png and mpeg to midi etc)

Dear friends,
i want some hint if i have diffenet images files of type .jpeg, bmp etc then can any one tell me how should i convert it to .png file
i searched the java api but i did not got any clue
similarly i have requirement for conversion of audio files to .midi format
and video files to .3gp format can any one send me java code or link to write such type of conversion code
it would be great help to me

Look into Java Advanced Imaging (JAI) and Java Image I/O for the image types, though I'm not sure that the codecs you listed are included in the basic package.