AC-3 (short for Arc Consistency Algorithm #3) is a type of Dolby Digital audio format. And the Dolby Digital is the common version containing up to six discrete channels of sound. The most elaborate mode in common usage involves five channels for normal-range speakers(20 - 20,000 Hz) (right front, center, left front, right, left surround)and one channel (20 Hz - 120 Hz allotted audio) for the subwoofer driven low-frequency effects. Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz.
AC3 audio is Audio Coding 3. The AC3 audio standard is being replaced with AAC, although AC3 audio will continue to live on for many decades due to the number of systems and networks which currently utilize it.
Unfortunately, AC3 is not supported on Mavericks. So, if you want to play AC3 audio files on Mavericks with QuickTime, you'll lose the sounds (AC3 audio). To solve the problem, one soluiton is to use another media player like VLC Media Player. The other solution is to convert AC3 to Mavericks supported audio format.
iOrgsoft AC3 Converter is a professional audio converter able to do audio conversion among different audio file formats like AC3, AAC, AIFF, FLAC, MP3, MP2, M4A, AMR, APE, WMA, WAV, etc. And it can rilp soundtrack from videos like MP4, MOV, AVI, WMV, FLV, etc.