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. ...
so .. you need to convert .mp4 to .webm or .ogv
another "solution"..you can replace NW.js ffmpeg.dll file..but
[quote:3g08fi89]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..