Fix yuv to nv21

[jameswestgate]

Fixes on issue with yuv conversion found on Pixel5, and improves performance of BarcodeReader.

[Denrage]

Appreciate the effort for that change! I actually tried that implementation before but it didn't work in the beginning for me bc i had a problem at another place, so i used the much simpler version bc that worked for my testing devices. Still don't know why exactly it only fails on specific devices and what actually fails there.
Did you test your implementation with other devices or only with the Pixel5?

[jameswestgate]

Still don't know why exactly it only fails on specific devices and what actually fails there.

Reading https://stackoverflow.com/questions/52726002/camera2-captured-picture-conversion-from-yuv-420-888-to-nv21, it seems that is an incomplete implementation. You can see in the new implementation that it tries to use that route for performance reasons if it can.

[jameswestgate]

Did you test your implementation with other devices or only with the Pixel5?

I also tested on my Samsung Galaxy S9 running Android 9.