Having better result with Quicktime video Engine than AVF and wondering why.

Hello.
It’s been almost a year now that I began exploring with Jitter.
I’m building quite simple patches to play around with video files in live situation.
Even though I don’t think that the kind of processing I’m asking for is very heavy, I always use the jit.gl method.
Mostly, I play video in loop, change the in/out points and play with jit.movie’s rate attribute.
And it works fine.

My question regards the AVF video engine. Everywhere on the forum, people seems to have great experience with this video engine. For my purpose, though, I have best result with Quicktime video engine and I’m wondering why?

As I mentionned, one of my preferred effects is playing with the it.movie’s rate attributes linked to an external controller. When using QT, the result is smooth and quite perfect.

If I use AVF as video engine the result is not fluid at all.
Buy the way, I always use .mov ProRes 422 files.

I also tried some months ago with the jit.gl.hap external and a hap encoded video files and did not get better results than with AVF,

Does someone had an idea why?
Does choosing a video engine depends on the use we plan to do with Jitter? Since I’m only dealing with video, maybe one engine suits my needs maore than yhe other?

I have join my patch so you can try for yourself, loading a video and playing around with the rate attributes and then swithcing video engines.
I’m wondering if I’m the only one having better result with Quicktime for this purpose.

Here is my computer specs :

MacBook Air (11-inch, Early 2014)
Memory : 8 Go 1600 MHz DDR3
Processor: 1,7 GHz Intel Core i7
GPU : Intel HD Graphics 5000 1536 Mo
OSX 10.10.5

Thanks a lot for your help and clues.

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