I have a bunch of QuickTime audio files (AAC mp4a 48 kHz) that play properly in OS 10.6 Snow Leopard, but are silent when played in OS 10.8 Mountain Lion. The playhead in QuickTime Player moves left to right, but the virtual VU meters do not modulate and no sound is heard. These same files do play in VLC Media Player, however.
Mac Pro, OS X Mountain Lion (10.8.1), AJA Kona LHe; Late 2010 MacBook Air
Do you have the latest (1.2.3) Perian?
<http://perian.cachefly.net/Perian_1.2.3.dmg>
Are you sure the audio in those files isn't AC-3? Perian won't play AC-3 in Mountain Lion. To fix, do steps 1 and 2 in:
Malcolm J. Rayfield wrote:
>> Do you have the latest (1.2.3) Perian? <<
Perian was installed when my Mac Pro was running OS 10.6 Snow Leopard; but I removed it after installing OS 10.8 Mountain Lion since Perian is not compatible with the new OS.
>> Are you sure the audio in those files isn't AC-3? Perian won't play AC-3 in Mountain Lion. <<
VLC will play the AAC audio files. It reports the following as their codec: MPEG AAC Audio (mp4a) 48 kHz
Incidentally, I get the same results (no audio) when attempting to play the QuickTime audio files on a MacBook Air that is also running 10.8 Mountain Lion. When I boot into 10.6 Snow Leopard on the same computer, the files do play properly in QuickTime Player.
Perian does wirk with Mountain Lion, except for AC-3 audio, but there is a fix for that.
I had the same problem then I asked the Genius Bar guys at Apple and they suggested MPlayerX (a free download). Just open all files with this program after installing it! Works like a charm for Mountain Lion glitches in QT.
QT audio does not play in Mountain Lion
