Dynamic bitrate Change on Tegra TX2 with MM API r32.1

I am currently implementing an HEVC encoding solution on TEGRA TX2 with the MM API r32.1 library.
I want to be able to modify the HEVC encoding bitrate without interrupting the output video stream (therefore dynamically).
But when I call the setBitrate or setPeakBitrate functions, I don’t see any change in the bitrate of the video produced.
On the other hand, the bitrate is well applied when creating the encoder.
The encoding parameters that I configure are the rate control (set in VBR), the IDR and the I Frame interval (GOP parameters), the HW Preset (I tried ultrafast or slow, it doesn’t change anything), the framerate and the VBV size.
What is the procedure to be followed to succeed in changing the bitrate dynamically as indicated in the documentation ?

Other question, when I try to change the QP (I, P, B) parameters with the setQpRange function, I don’t see any change in the stream while the setConstantQp function is working !
What must be done for these settings to be active?

For dynamic bitrate change, we suggest run in CBR mode. Please try this sample to check the functionality:
Allocating a GstBuffer of type "memory:NVMM" - #15 by DaneLLL

And now the latest production release is r32.5.1(Jetpack4.5.1). You may consider to upgrade to newer release.