Wondershare claims conversion speeds up to than standard software, depending on your hardware.
An extremely powerful, free tool based on FFmpeg. It handles almost any codec under the sun and offers a direct portable version. VLC Media Player (Portable): wondershare uniconverter portable better
If you work in a secure environment (medical, legal, government) where IT policies forbid installing unapproved software, the portable version often slips through the cracks because it requires no admin rights. You can run it from an encrypted drive, convert sensitive video evidence, and then remove the drive. No traces remain in the Windows Event Log or uninstall list. Wondershare claims conversion speeds up to than standard