UAC2: no feedback stream on Windows

[mastupristi]

hello, I am imlpementing a kind of USB sound card. I'm having problems on Windows that don't seem to be there on Linux.
So I have a super-simplified version of my descriptors that I attach: it is simply an interface containing an OUT data EP and an IN explicit feedback EP:

• Interface 1 containing 2 endpoint:
  • EP 1 OUT: Isochronous, Async, Data
  • EP 1 IN: Isochronous, No sync, explicit feedback

When I try on Linux I can see the feedback packet using Wireshark, and furthermore I see that the host (the PC) chases the clock of my board even when it changes (I implemented a command to change the clock up to +/- 2000ppm, just to test the clock chasing by the host).

Instead, when I try on Windows (10) no feedback packet is traced by Wireshark and, in fact, after a few seconds the audio begins to glitch.

Can you help me understand where I am going wrong?

I was also thinking of trying implicit feedback, but then I read this https://github.com/MicrosoftDocs/windows-driver-docs/blob/staging/windows-driver-docs-pr/audio/usb-2-0-audio-drivers.md#audio-streaming

so I won't even try that.

regards
Max

usb_desc.zip

[mastupristi]

As suggested here:
https://learn.microsoft.com/en-us/answers/questions/472332/explicit-feedback-for-asynchronous-audio-with-usba

feedback started to work as soon as the interval was set to 1

best regards
Max