export video with 24-bit audio

I’m working on a video project in ardour4 and I want to export to 24-bit using pcm_s24le, but the export dialogue only provides pcm_s16le. is there a way to export the audio to pcm_s24le in a video?

The video export feature currently only supports 16bit audio.

if you really need this high fidelity you’ll be better off exporting the audio only and mux the audio/video with a dedicated tool appropriate for your use-case.

While ffmpeg (which comes with ardour) can do it, Ardour’s video-export dialog only offers a very tiny subset of ffmpeg’s vast potential. It is mainly intended for dailies or quick exports.
There may or may not be additional parameters in the future (please file a feature request on tracker.ardour.org so that it won’t be lost), but note that properly muxing/master/transcoding video is a science by itself which is outside the scope of Ardour.