Facetime crash on ring

Okay, so my iMac 5k retina is connected to my 5.1 AV reciever via optical toslink cable. Everytime I watch video files in VLC in 5.1 surround (DTS or DD) and I get call on facetime it crashes on ring. I play with VLC option thicked encoded digital output. When i play regular stereo video files it does not crash on ring. Whats the problem?

Thanks

Here is the crash log:

Process: FaceTime [654]

Path: /Applications/FaceTime.app/Contents/MacOS/FaceTime

Identifier: com.apple.FaceTime

Version: 3.0 (2701)

Build Info: FaceTime-2701000000000000~12

Code Type: X86-64 (Native)

Parent Process: ??? [1]

Responsible: FaceTime [654]

User ID: 501

Date/Time: 2016-05-20 08:12:40.334 +0200

OS Version: Mac OS X 10.11.5 (15F34)

Report Version: 11

Anonymous UUID: 717CD7EE-BF86-EC23-9D92-F1957C3236BC

Time Awake Since Boot: 1800 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGSEGV)

Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000

Exception Note: EXC_CORPSE_NOTIFY