Now.... after all that brouhaha... that is still nowhere near finding out what's what with Safari not supporting webm, now is it?
Lastly... "Matroska video" - from earlier without Perian installed - this FAILED miserably... wants to use Perian to somehow open in QT Player
I'm actually starting to get a headache trying to follow the various explanations, so if you will allow, I'll simply post my understanding of the situations:
Basically, a media file is playable if, and only if, three requirements are met:
- The target system is configured to recognize and support the media file format (container),
- The target system is configured to recognize and support the media file compression formats contained within the file type, and
- The playing software (media player, browser, plug-in, etc.) is programmed to recognize and process the combination of file type and codecs used.
Since each software manufacturer is free to program their software as they think best, individual users are free to configure their systems as they please, and web site programmers are free to post content in any file format and compression format they choose on a web page programmed for playback in any manner they choose, there are quite a number of possible permutations when it comes to playback possibilities on any given system.
In the case of the WEBM file, neither QT X nor QT 7 natively support the playback of On2 VP8 video or Vorbus audio content. On the other hand, if Perian is installed, then the QT 7 player and the QT 7 plug-in can play this content employing user added support software. Unfortunately, the QT X player cannot access the Perian support for playback purposes and is not programmed to use it for conversion purposes. As to whether or not HTML5 WEBM programmed Safari playback is possible, it is impossible to tell at this point since the order of your playback test conditions automatically selects the first HTML5 (MOV file) option for my system—thus it never reaches the WEBM test. (I.e., you would have to try reversing the order of the playback tests (or simply delete the first option to see if the HTML5 WEBM option is also viable in Safari v8.0.6 on my system.)
With regard to the Matroska file type, in this case it is the file type that is not natively supported by either QT X or QT 7 embedded OS structures. Once again, if the Perian codec package is installed, QT 7 based software can process/play the files but QT X based software cannot play or convert the content since the software is not programmed to recognize/handle MKV files even when the compressed data is compatible.
As to why systems with the same OS handled files differently, you have yet to indicate how these systems are have been user configured for codecs and file types nor traced, in all cases, which resource file is actually being accessed or how. E.g., to actually test the WEBM file version, I had to manually access and download the media resource since the manner in which the alternate web pages are programmed controls which files are accessed by the different browsers. (E.g., entering the URL http://dig1.gcsu.edu/frank_lowney/ipod/letterman/letterman_GC&SU_iPod_H264.webm in Safari automatically downloads the WEBM file but if I enter the URL http://dig1.gcsu.edu/frank_lowney/ipod/letterman/ then the web page automatically plays the MOV file using HTML5 at HTML5 defined dimensions but entering the complete http://dig1.gcsu.edu/frank_lowney/ipod/letterman/letterman_GC&SU_iPod_H264.mov URL plays the MOV file via the plug-in at the file's own encoded playback dimensions. Therefore, recommend the original poster program and test web page coding, media content, and browser combinations individually and one-at-a-time in oder to achieve his goal—whatever that may be. (I.e., I still don't know if your goal is to avoid plug-in failure modal messages or the coding of your web page for use by all possible bowsers on all possible platforms, using all possible configurations for a specific form of media or something else entirely different.)