The target aspect ratio setting affects the selected resolution of the source stream for the Preview use case. Did you use
PreviewView for the Preview use case? PreviewView's default scale type setting is
ScaleType#FILL_CENTER. It will scale the source stream image to fill the output view. Therefore, no matter which target aspect ratio is set, you will see the output view fully filled. Maybe you can change the scale type to
ScaleType#FIT_CENTER. Then, you will see the source stream images that are displayed centrally inside your output view and the aspect ratio of the source stream is maintained. If my assumption about the usage of PreviewView is incorrect, please let me know and provide more detailed information so that we can clarify the issue. Thanks.