It is also possible to generate sound files "offline", meaning sound generation does not have to be in real time, or live. For example, the input could be a MIDI file and the output could be a WAV file or an MP3 file. Playing a WAV or MP3 file simply means playing a precalculated waveform. The advantage of offline synthesis is that the software can spend as much time as it needs to generate the resulting sounds, potentially increasing sound quality. It could take 30 seconds of computing time to generate 1 second of real-time sound, for example. The disadvantage is that changes to the music specifications cannot be heard immediately.