it would take a very small amount of time for the nvidia developers to put this functionality in nvidia-settings
I thought the nvidia-settings application was open source, so if the nvidia devs won't do it, there is always the possibility someone else will do it.
An option in xorg.conf would be much more familiar to most users than setting environment variables I think.
Really? Well, I think setting environment variables is part of basic linux knowledge. If you have enough knowledge to manually edit configuration files you should also know how to set environment variables.
Apart from that, I wouldn't want to edit my xorg.conf and restart the X server every time I change this setting.
EDIT: Setting VDPAU_NVIDIA_SYNC_DISPLAY_DEVICE to the correct value (DFP-1 in my case) seems to work nicely. I have to tearing even with a compositing manager running. Thank you very much for pointing this out. Unfortunately the nvidia README is quite
lengthy and it's not easy to find what you are looking for.
By the way, to find out the correct identifier for your display device simply open nvidia-settings and head to the "Display Configuration" tab. The identifiers are listed in the "Model:" drop-down box.
Instead of integrating the sync option into nvidia-settings or xorg.conf wouldn't it be a good idea to make an API function for that? The video player application could set the correct value either automatically or via a user-defined setting. I think this way would be most convenient for end-users.