Based on the <some things> I've observed
- virtualized graphics is substantially poorer than real mode so it's actually best to implement <zero> graphics in the Guest. Do your transcoding in the Guest if you wish, but view the results in real mode (another physical machine or perhaps the Guest).
Re: keyboarding conflicts... I'm going to guess that they likely relate to GUI windows. If you follow my recommendation to not use a tool that way (most transcoding apps support command line even if they can be deployed in a Desktop), they wouldn't be an issue. Typically you just build your command and execute.
If you're trying to do something else than transcoding, eg video slice and dicing...
YMMV. Depends on your hardware. Depends on the app. Depends on a lot of variables.
HTH,
Tony