Embedded QuickTime files not playing sound

Question

I'm having trouble getting older, embedded QuickTime files to play properly. Many of them do play but without sound.
An example:
The embedded QuickTime files in questions 6 and 10 here...
http://www.linguistics.ucla.edu/people/schuh/lx001/Web_Quizzes/Quiz_07/07web.htm l
...do not play sound.
When viewing the files directly...
Example: http://www.linguistics.ucla.edu/people/schuh/lx001/Web_Quizzes/Quiz_07/07_Quiz_m edia/0706_split_brain_red.mov
...the sound plays properly.
I have done a bit of playing around on a few different machines and have found the following:
2009 MacBook Pro: video and sound play correctly in Safari and Firefox
OS X: 10.7.5
Safari: 6.1.6
Firefox: 36.0 with QuickTime Plugin ?
QuickTime 7: ?
QuickTime X:10.1
2009 Mac Mini: video and sound play correctly in Safari and Firefox
OS X: 10.8.5
Safari: 6.2.3
Firefox: 33.1 with QuickTime Plugin 7.7.1
Firefox: 36.0.1 with QuickTime Plugin 7.7.1
QuickTime 7: 7.6.6
QuickTime X: 10.2
2011 Mac Mini:  video and sound play correctly in Safari and Firefox
OS X: 10.9.5
Safari: 7.1.3
Firefox: 31.0 with QuickTime Plugin 7.7.1
Firefox: 36.0.1. With QuickTime Plugin 7.7.3
QuickTime 7: 7.6.6
QuickTime X: 10.3
2011 iMac: no sound in videos, improper display of video with menu in both Safari and Firefox
OS X: 10.10.2
Safari: 8.0.3
Firefox: 36.0.1 with QuickTime Plugin 7.7.3
QuickTime 7: 7.6.6
QuickTime X: 10.4
2011 Mac Pro: no sound in videos, improper display of video with menu in both Safari and Firefox
OS X: 10.10.2
Safari: 8.0.3
Firefox: 36.0.1 with QuickTime Plugin 7.7.3
QuickTime 7: 7.6.6
QuickTime X: 10.4
Is this a Yosemite issue? Not being able to play older QuickTime 7 files properly? I'm not sure what else the issue could be since everything seems to work fine in 10.7, 10.8, and 10.9 (unfortunately, I have been unable to test this in 10.10 or 10.10.1). Maybe I'm overcomplicating a simple issue? Any help would be greatly appreciated.
Thanks!

Answer 1

Is this a Yosemite issue? Not being able to play older QuickTime 7 files properly? I'm not sure what else the issue could be since everything seems to work fine in 10.7, 10.8, and 10.9 (unfortunately, I have been unable to test this in 10.10 or 10.10.1). Maybe I'm overcomplicating a simple issue? Any help would be greatly appreciated.
Some very interesting observations which peaked my own curiosity due to on-again, off-again nature of the playback. I suspect this is either a "bug" or represents content handling changes that are currently in the process of  "evolving." Not a web site programmer so I used iWeb to run some contrast-comparison tests on how audio was handled by the plug-in software when directly accessing the content by its URL and via the page embed strategies. My results mirrored yours in that:
1) All legacy codecs tested (A-Law, IMA, QDM2, QPV, and u-Law) in an MOV file container played correctly in the QT 7 player.
2) The same files all played correctly when content was accessed by the plug-in software directly using the URL reference.
3) None of the files containing legacy audio compression formats would play audio using the plug-in software using a web page embedding strategy.
4) An MP4 (H.264/AAC) version of you original clip played correctly in all instances.
5) Replacing your QDM2 audio track with an AAC audio track in the original MOV file allowed the file to play correctly in all instances.
Based on these observations, I suspect the problem is in the way the software is currently programmed to handle (or rather ignore) the embedded strategy content. However, as you indicated, it is probably time to update your files. Not only did the H.264/AAC version of your original file play in all instances, but it used less than 45% of the file space/bandwidth for the settings I employed as compared to your original "0706_split_brain_red.mov" original file.