I had tried to remove touchStartID. But the usage will be very strange. There are few strange cases. 1. User puts two finger on slider with video playing and lifts one finger the video, the player becomes playing while another one still touched. 2. User puts one finger on slider while video playing and touches play button, the player becomes playing while another one still touched. This makes also the touchmove and touchend more complex to handle it.

I think it will be fine to support multiple finger touching on buttons. But if we need to handle move and end, it will be come complex to make it correct.