4K video encoding on Xavier

Is there a good reference out there about what exactly the Xavier AGX can encode as far as video is concerned? The only spec that I can find is: “Encoder/Decoder (2x) 4Kp60 | HEVC/(2x) 4Kp60 | 12-bit support”

I’m trying to record 4x 4K 30fps cameras at the same time but am only able to process 15 frames per second reliably. I had assumed that the spec above meant that I could encode 120 4K frames per second so could have as many streams as I wanted as long as their total <= 120 fps. Am I wrong about that?

We have verified the case with the camera board(LI-JETSON-IMX274-xxx) from our partner. There are two sensors on the board and each sensor can run 4Kp60.

One concern is there are actually two NVENC blocks in Xavier, so single encoding process cannot achieve 4Kp120. Has to be two 4Kp60. For hardware architecture, please check technical reference manual of Xavier: