Decoder hwaccel flag is too simplified #101
Description
Recent commit 5504d7b simplifies how hwaccel flag works. Now it is a boolean. Unfortunately this leaves less control for the end user and can lead to problems.
For example we target CUDA in our code and if we set environment variables like: DISPLAY=:0 it will assume 'vdpau' as our hardware target.
Having a possibility to specify 'cuda' manually would be less error prone for us.
Simply reverting that commit would fix our issue.