fallback from "Use only decoder" mode for NVENC

[Selur]

I have no clue what such a fallback should do.

NVEncC has no option that allows to first test hardware decoding and if that fails automatically use software decoding.

Only thing that comes to mind I could do is add some checks to abort the job creation, if NVEnC + 'use only decoder' is selected, but the input is not one of these formats:

• MPEG-1
  
• MPEG-2
  
• VC-1
  
• VP9
  
• H.264
  
• H.265
  

see: https://github.com/rigaya/NVEnc/blob/mas....md#--avhw

Cu Selur