I have 2 PCs, both with a 64 channel madi card.  Machine 'A' is runing Win7, and the RME TotalMix is running showing what is on each channel.  I am also running Reaper, which has a plugin generating tone on the 1st 8 channels which is visible on the TotalMix.

Machine 'B' is a dual boot Win7/Ubuntu 16.04, and when booted into Win7, the tone coming in on the madi stream channels 1-8 is clearly present and audable.  When I boot into Ubuntu, I run QjackCtl and start Jack.  I then start a simple program I have written from a tutorial I found that copies from the inputs to the outputs.  Unfortunately, nothing is received on the inputs.  On the outputs however if I fill the output Buffer with random numbers, the resulting noise appears on machine 'A', so not everything is a total disaster.

I have checked alsamixer for muting on the inputs and am now at a loss for possible causes. (I am summing the abs value of each frame in input and periodically printf the total, which is always zero.

Could someone more knowledgeable that myself suggest causes for the lack of input.

Zappa Fan. (mostly to make searching digests easier, but also true).