16K with count = 4, means every socket of the multi side will have count * number of multi-sockets of 16 KB.
If you have one to many (2) channel; it will mean 2* 4* 16 KB
Are you creating any other channel in the FX3 firmware? What is the error code returned by the channelcreate API? Please attach your firmware if possible.
We were able to set the size and buffer count correctly. The code is based on cypress sample for UVC.