I came across this line of sheet music, and I've never seen these hollow "x" shaped noteheads before. I found it in this search engine, and the title or lyric seems to be in Chinese. I wasn't able to playback the MIDI example since it requires the now out-of-use adobe flash. I would love to know what instrument this type of notation is intended for and what these x shapes indicate.
I've tried google searches, both ones describing the notehead shape and also copypasting the Chinese characters. But since I don't know any Chinese whatsoever I wasn't able to figure out whether any results had anything to do with this piece of music.
I suspect they aren't rhythm notation, since they show different notes.
Since this is my very first post here, I hope I have provided the right amount of information; otherwise please let me know.
EDIT: I have now, thanks to a suggestion from user Laurence Payne, downloaded and listened to the MID file and it doesn't sound like an actual piece of real music. The note heads were changed to common ones in my software, but the melody itself sounded strange enough to suspect it is simply some test music written down. This, in addition to several notation errors pointed out by users, makes me think that an exact answer might not exist. I thought these were some type of notation with a fixed meaning, but it seems that may not be the case. But if someone happens to know differently, I'm curious of course.
I have been sent this question as a suggestion for a possible answer. The reason I haven't acknowledged it, is due to the answers there consisting of guesses rather than certain answers.