Get ffmpeg working with dual GPU setup:
=======================================
ffmpeg does not work with many NVIDIA graphics cards, but can work with Intel's. this is the setup to get ffmpeg Intel commands to work when NVIDIA graphics card is enabled.

1. Make sure Intel and NVIDIA drivers are installed.

2. install this:
    sudo apt install libva-dev

3. Install Intel Media SDK for ubuntu 20.04 by:
    git clone https://github.com/Unit-X/Intel-MSDK-Ubuntu20-04-Installer.git --depth=1
    cd Intel-MSDK-Ubuntu20-04-Installer
    ./install_msdk1.sh
    (If finished with no errors)
    sudo reboot now
    (cd to Intel-MSDK-Ubuntu20-04-Installer directory)
    ./install_msdk2.sh

4. When running the command (ffmpeg), add "DRI_PRIME=0" before the command to work
    example:
    DRI_PRIME=0 ffmpeg -hwaccel vaapi -hwaccel_output_format vaapi -hwaccel_device /dev/dri/renderD128  -i input.mkv -acodec flac -compression_level 8 -ac 2 -c:v hevc_vaapi  new.mkv

Sources:
https://trac.ffmpeg.org/wiki/Hardware/QuickSync
https://github.com/Unit-X/Intel-MSDK-Ubuntu20-04-Installer

Date: January 27th 2022