Having seen several post about this on the Samsung boards. Happened to my wife's phone overnight. There is absolutely NO sound and any video accessed will only play on fast forward.
I have tried safe mode and done a factory reset. No change. There appears to be a bug in the latest update Verizon sent out, and since both Verizon and Samsung have the phones locked down, there is no way to revert back.
And before anyone asks, Quiet mode is off, the volume is turned all the way up. The phone worked just fine when we went to bed last night. Now it is not working.