Why does java not allow the process to run?

Question

Java

There is a process running through java that processes files and videos. Works great, as long as you don't know the state of the process with while(p.isAlive()) or wait for it to finish with p.waitFor(). In such cases, the task manager says that it consumes 0 processor time. And the work ends in the middle. + The process is still in the task manager. Without state recognition, it works as it should. FFMPEG.EXE Process

Runtime runtime = Runtime.getRuntime();
        Process p = null;
        try{

        p = runtime.exec(new CommandGenerator(new File("C:\\Users\\Denis\\Desktop\\sx\\ffmpeg.exe"), 
                new File("C:\\Users\\Denis\\Desktop\\sx\\Wildlife.wmv"), new File("c:\\Users\\Denis\\Desktop\\output"), 100).generateParam());
        p.waitFor(); или while(p.isAlive()){};
        }catch(Exception e){
            e.printStackTrace();
        }
        
        System.out.println("УРА!!!");