W
video is missing sound
lumia 930 videorec ton hardly listen to
Are you using Windows 10 Insider or 8.1 Official?
Open Camera , settings, video.
Have you tried recording with Surround Sound toggled On & Off? No sound with either setting?
You may have a hardware issue. To help rule out software all together you should Hard Reset your phone.
Power off the phone > hold Volume Down > press Power > keep holding Volume Down until you see the exclamation (!) screen, then immediately release the Volume Down
Now tap Volume Up / Volume Down / Power / Volume Down
You should see the spinning gears and your phone will reflash the last OS version held in recovery. You do loose data, but get your phone back. Sign into your Microsoft Account and restore your backup during the set up.
If the problem persists, it is probably hardware. seek repair.