Hi everyone,

my name is Marco, from Italy. I'm a developer that recently got an 
interest in improving the current situation of audio in qemu/kvm.

I've been working successfully on multiple patches for Scream 
(https://github.com/duncanthrax/scream 
<https://github.com/duncanthrax/scream> ), a virtual sound card for 
Microsoft Windows, that allow to transfer audio from a Windows VM to a 
Linux host. The project initially supported only stereo sound over the 
network, but with my patches now it support up to 7.1 surround and it 
can transfer the audio samples using shared memory between the VM and 
the host (based on IVSHMEM), for lower latency.

Now that was a good project, but I want to do more. I dream of an 
virtio-audio device that can handle multichannel audio in and out of the 
VM, to be used with more guest OSs than just Windows.

I know I have a long way to go to reach this goal, but I'm motivated and 
willing to learn. I admit I don't have much experience with the qemu 
source code or the virtio source code, but I learn fast.

My work on Scream was to familiarize with Windows driver development, 
VM-to-host communication and low latency audio processing.
My idea is to start with small self-contained projects to familiarize 
with the source codes of the various projects and gain the experience I 
lack, then moving on the real virtio-audio project.
This way I can both obtain more knowledge on the subjects and help the 
open source community that over the years have done so much for many.

As we speak I'm reading the VirtIO documentation, where I've found out 
that I need to require a new device number for this project (Appendix 
B.3). So, here I am.

I'm not quite sure if this email is enough to obtain a new number or if 
I need to follow some process I'm not aware of. In the meantime I'm 
using the device number 65535 as documented in the specifications.

Looking around I've seen there is a recent issue on GitHub to reserve a 
virtio-audio device id, and a patch was submitter to assign id 25 to 
audio devices.

I'm not sure how this works, is that number already assigned and I 
should use that or should I get a new one?

For last, I have a question to clear the things up for me. It is my 
understanding that in this mailing list you discuss about the 
specifications, not the actual code. What's the usual process when 
writing a new virtio device?
Should I start with writing the code and then document how it works or 
is it the opposite? Should I document it and have it approved and then 
implement the specifications?

I know that this may sound like a stupid question, but please be patient 
with me, it's my first time.


Best Regards,

Marco