IOS setPlaybackQuality not working with YouTube Helper Library

Question

I tried many solutions, such as YouTube’s iFrame API and setPlaybackQuality "or" suggested Quality "doesn’t work . But now it doesn’t work. I updated the helper library so far. Was setPlaybackQuality () was no longer supported on a mobile device (for example, iPhone) ? How does iPhone now change the quality of YouTube videos?

Thanks.

EDIT:
2015-01-21
1. I tried calling player.loadVideoById: startSecond: suggestQuality with hd720 during the PLAYING state. But it still turns into average quality.
2. I tried calling player.setSize (1280,720), it changed the quality to hd720! But the visible area of ​​the video is outside the current viewing border of the player (for example, 320x180).

Any solution is welcome. Thanks.