Betterplayer video screen is black but sound is playing

I download the code of better player from https://github.com/jhomlala/betterplayer and run it with flutter run in my IOS and android emulator. The normal video player works but the better player shows a black screen on IOS iPhone and some video needs to load too long on IOS and Android. Android can play the videos which IOS can't play and IOS can play the videos which Android can't play. I can't figure out what is going wrong because I don't change anything with the code of better player and there are no errors printed in the console. For running in emulators I used iPhone 13 and Pixel API 31. The Code isn't changed from https://github.com/jhomlala/betterplayer and the IDE I am using is VS Code. I also tried to run the code on other laptops but also don't work. Now I don't know what I did wrong and hope somebody can help.