Home Movies

My Apple TV is attached to a 77" 4K TV. We enjoy watching home movies on that TV that are streamed by the Apple TV from my MacBook Pro on the same network. The recent 4K and 1080p videos look great, but the older, lower resolution movies all are enlarged by the Apple TV to fit the screen and have jaggies and don't look good. Our 20 year old movies are 640x480. When I watch them on the MacBook using QuickTime Player, the windows are small and the images are sharp. We'd rather watch a sharp movie in a small window than watch a suboptimal image that fills the screen (at least the 4/3 aspect ratio) on the TV. Can this be accomplished with the Apple TV and big-screen TV? I couldn't find anything in the big-screen menus to help. Thanks.