convert jpgs and mp3 to flv using java-Collection of common programming errors

I am not sure if this would be relevant to you, but I think it would be helpful:

use java-ffmpeg wrapper, or simply use java runtime to execute ffmpeg? and more precisely the answer with the highest score:

http://stackoverflow.com/a/1281454/1091386 which is, of course, 4 years old. Following the second link to the forum thread http://red5.5842.n7.nabble.com/java-call-ffmpeg-td25005.html seems to suggest something like

Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("ffmpeg");

might work for your case. Of course, you will want to pass in options separately…