I think this is a problem:
NW.js Documentation
[quote:257u1zqn]Using MP3 and H.264 codecs requires you to pay attention to the patent royalties and the license of the source code. Consult a lawyer if you do not understand the licensing constraints and using patented media formats in your application..
...
Due to the license issue, the prebuilt binaries of NW.js doesn’t support proprietary codecs, like H.264. ..
So you can’t play MP3/MP4 with <audio> and <video> tags with prebuilt NW.js. ...