Hi,
The format is not included in nvvidconv plugin. The plugin is open source and would need to customize and rebuild the plugins. The source code is in
Jetson Linux R32.7.1 Release Page | NVIDIA Developer
L4T Driver Package (BSP) Sources
Please download the package fitting your release version.
Or may customize nvv4l2camerasrc to support YVYU. Here is a patch for changing to YUYV for reference:
Macrosilicon USB - #5 by DaneLLL