title: How to specify file type in ffmpeg (-f) for both the input and output?
body: <p>I'm using ffmpeg to convert the stdin (pipe:0) to stdout (pipe:1).
  My input format is "s16le" and my output format is "wav".
  How do I specify the two different formats in an ffmpeg command? </p>
  
  <p>I'm also using two different frequencies (-ar), input 44100Hz and output 22050Hz, how do I specify the two different frequencies in an ffmpeg command?</p>