ofAVFoundationPlayer slow setPosition

[i-n-g-o]

calling setPosition() on ofAVFoundationPlayer is slow.
this is due to synchron disposal of resources (AVAssetReader).

disposing AVAssetReader on a backgroundThread (dispatch_async) would solve that issue, but has problems when called too quickly after each other. (in my case updating the position every 100ms works, but leaks memory (??!!) when calling every 50ms)

this needs further investigation.

fast-seek (async disposal) can be found in this branch:
https://github.com/i-n-g-o/openFrameworks/tree/ofAVFoundationPlayer_fast_seek

[i-n-g-o]

i see the memoryleaks with a 1080i50 file encoded with ProRes422

if ((ofGetElapsedTimeMillis() - timeLastLoaded > 50)) {
    fingerMovie.setPosition(ofRandomuf());
    timeLastLoaded = ofGetElapsedTimeMillis();
}

[dimitre]

Potentially fixed by
#6797
#6791
one addresses the "infinite threads" issue and the other on some seek position issues.