If possible, an option in Voukoder to render only audio in Vegas. The screenshot below is just a suggestion.
In Premiere, you can choose render only video or audio in the rendering templates panel.
In Vegas, is not possible choose render only audio in the render templates panel, even if the all video events or the all video track are disabled.
When all video events are disabled in menu Options/Mute All Video, the voukoder is displayed in the render templates panel, but it doesn't render just audio, it also renders a black video.
When all video tracks are disabled Voukoder is not displayed in the encoder list in the rendering templates panel.