s = single("/path/to/movie.mkv")

# Copy first audio track and video track
# and re-encode second audio track:
output.file(
  %ffmpeg(
    %audio.copy,
    %audio_2(
      channels=2,
      codec="aac"
    ),
    %video.copy
  ),
  "/path/to/copy.mkv",
  s
)