Hello.

My use case is to run several Skype instances in RDP session connected to a remote machine. However the redirected microphone is not available inside of a sandbox.

It can be reproduced not only with Skype, but with a stock Sound Recorder application included in Windows 7.

The setup involves two virtual machines, I am using VMware Workstation 8.0.2. I will call the first machine as server and the second one as client.
The server runs Windows 7 Ultimate Service Pack 1 with the latest security and recommended patches applied. The client runs Windows XP Service Pack 3 with the latest security and recommended patches applied. The client machine also has a RDP Client 7.0 installed and CredSSP enabled. Sandboxie 3.68 is installed on the server. The user account on the server is of the admin type. UAC is turned on in the most paranoid mode. The fact that Windows XP is used on the client seems to be not important. It is also reproducible when connecting from Windows 7 to Windows 7.

Steps to reproduce:
1. Connect to RDP session from client to server using Remote Desktop Connection application. Use redirect microphone setting when connecting: Options => Local Resources tab => Settings button => Remote audio recording => Record from this computer. Ensure that you have a microphone connected to client machine, either built-in to a webcam or a separate, plugged into a 3,5mm jack.
2. Run Sound Recorder. Record some words and play the recorded sound back. This will ensure that the microphone redirection works outside of the sandbox.
3. Create a new sandbox and run Sound Recorder inside of it.
4. Repeat step 2, but for the sandboxed Sound Recorder. It will be unable to record any sound because it does not detect a recording device.

Skype does not detect the redirected microphone in the same way. But after playing around for a couple of hours and after a numerous reboots and random tweaks, I was able to run several Skype instances side-by-side inside of several sandboxes and the microphone WAS detected in each. But it lasted only one time until logoff from RDP session. I believe some race conditions are involved in this.

If I ran several Skype instances in sandboxes directly from the console, everything works as expected. I can even call one Skype instance from another and get a bunch of echoes when pronouncing some random words

I didn't set up the same scenario that you describe, but when I tried RDP'ing into an XP computer, it doesn't have an audio recording device, i.e. the RDP doesn't forward the local microphone to the remote system. I did use the "record from this computer" setting in RDP.

In any case, the first thing you can try is to go to Sandbox Settings > Restrictions > Hardware Access and check the option Permit programs to manage hardware device configuration. I'd like to know if this makes a difference.

The Terminal Server component of Windows XP does not support microphone redirection at the server side. So you need Windows 7 as and RDP to test this.

Also I tried to relax hardware restrictions for the sandbox as you suggested, but it did not help, the microphone is still not available.

Actually, I have found a workaround. I gave skype.exe direct access to IPC by entering '*' as resource name. Several skype instances can coexist peacefully and have access to redirected microphone. However, this is too insecure.


I tried to hunt down the correct IPC object but failed. I enabled tracing and launched the old good DebugView (remembering the old days of Windows NT kernel mode driver development course). I enabled only IPC/Deny. I experimented with Sound Recorder.

Without *, I got these lines from SBIE before "An audio recording device cannot be found." messagebox from SoundRecorder:



With '*" configured for soundrecorder.exe, I got the same lines!



The "most restrictive" working resource mask for IPC objects I could find was "\*\*\*"

What am I doing wrong in finding the IPC object?

You say you configured "*" for soundrecorder.exe, so it's possible the (ID) lines that you still see are coming from some other process. Did you check if process 3140 (as appears in the second log) corresponds to soundrecorder.exe?

Also thanks for the tip about XP vs Windows 7, I will give this another try.

Any news for this issue?

I couldn't get RDP into a Windows 7 virtual machine to communicate the audio like you say it should. Maybe there is something in the virtual machine drivers that isn't compatible with remote audio. Also when I googled it, there isn't clear documentation about this. Official documentation only talks about using this in the context of a Windows Server, unofficial suggestions on forums suggested to use a registry tweak, but I couldn't get any of that to work. Sorry.

So no effect if you try to apply these hints?
http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1004839
http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&externalId=1003425
http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&&externalId=1007996
http://bloogish.com/285/remote-desktop-microphone-redirection/

I already tried the suggestions in the first and last links. The suggestions in your second and third links don't seem relevant.

If you want to help, try to get remote audio working on your test setup, and let me know what you did to make it work.

You can try this third-party solution for redirecting sound input into RDP session: http://www.sound-over-rdp.com/