how does Xavier support hardware-accel decode for cuda10? No found

I am going to compile ffmpeg to support hardware-accel cuvid decode, but cuda10 has not please help where to find the document?

The Xavier doesn’t do video decode using the GPU resources; it has dedicated video encode and decode circuitry.
You can see how to use them in the video_encode and video_decode samples installed in the nvidia home directory on the device.
(They use the Video4Linux video decoder/encoder driver interface, although there are a few parameters that look NVIDIA-specific.)

The hw video encoder/decoder is also accessible through GStreamer, please refer to the L4T Accelerated GStreamer User Guide for examples.

You can take a look at and the samples in ~/tegra_multimedia_api folder of the target device.