Cubase 10.5 VST3 Silence Flags bug

Developer VST 3 SDK
1

Hi,
I have added support for the VST3 ‘Silence Flags’ to my plugins, but they are crashing with an assertion due to the input buffer not being silent.

Steinbergs documentation states: “The host has the responsibility to clear the input buffers (set to zero) when it enables the silence flags”.

However I launched Cubase Studio 10.5 with a breakpoint in the process method.
The DAW passes my effect the silence flag: 0x00000000ffffffff which I interpret to mean “All inputs are silent”. However looking at the input buffers, they are filled with the following alternating pattern (which is not zero):

|||[0x00000001]|-1.00000001e-10|float|
|||[0x00000002]|1.00000001e-10|float|
|||[0x00000003]|-1.00000001e-10|float|
|||[0x00000004]|1.00000001e-10|float|
|||[0x00000005]|-1.00000001e-10|float|
|||[0x00000006]|1.00000001e-10|float|
|||[0x00000007]|-1.00000001e-10|float|
|||[0x00000008]|1.00000001e-10|float|

…etc

So If am correct - Either the documentation is wrong, or Cubase Studio 10.5 has a defect?

Any guidance is much appreciated,

2

The documentation is wrong. The buffer is set to a value identical to silent (something near zero).
This is done to prevent de-normalization .

3

Thanks, I thought it might be for denormalization.

What I’ve done in my plugin, is when Cubase sets the silent flag I substitute the DAW-provided buffer with a pre-prepared buffer full of zeros. This prevents my plugin from asserting.

(my plugin disables denormals via an FPU flag anyhow).