quicktime player and h264 encoding

[mattes]

I am encoding live stream with gstreamer using h264 codec
for playback with Quicktime Player.

It works fine with lower resolution. Though when I encode in larger resolution 720p up,
I notice a drop of performance on the playback end with QTP. Typically it results in lower playback
framerate, Recording at 1080p @ 30fps, will result in playback frame rate below 20fps.

Quicktime Player seems to be really picky about the media codec.
Are there an special option needed/required for 'x264enc' to improve
the Quicktime playback expirience?

mattes