[Frederic Baumann] "I have QuickTime 7.6.8 installed. QuickTime versions were an issue with VP9, is it still true?"
No evidence - yet.
When apple updates QuickTime, they only test within their own universe and to hell with everyone else. Other NLE programs get caught with similar issues when Apple ups a rev.
How about posting a few seconds of the iPhone video for everyone else to test?
Steve Mann
MannMade Digital Video
http://www.mmdv.com