iOS settings: ScaleEngine Video CDNHigh Profile 4.2 and Keyframe Every 2 seconds

Here are  the specifications for HLS Authoring.

* AVC/H264 
* Level and Profile 4.2 or less
* Prefer High Profile over Main or Baseline
* Keyframe every two seconds

The apple developer pages on ios settings are the best references, but in general, following the above settings in your encoder will get you smooth, high quality video on iOS devices.

If you are streaming low bitrate video, you need to send 10 fps only, with keyframe every 30 frames, if the video stream is under 200kbps. For 200 to 300kbps, you want 15 fps and keyframe every 45 frames.