@Dreu-Leake that's an ffmpeg-library parameter whose licensing prohibits commercial apps like Vegas from employing their code. To get ffmpeg rendering from Vegas you need a 3rd Party plugin like the new Voukoder Pro, the old free Voukoder, or DebugMode Frameserver. Note that the old free Voukoder only supported up to vp22 and is no longer available from the developer. The old Frameserver is still available but a vp23 version is under active development and expected to be released soon.