The setup:

Plantronics USB CS50 Headset > USB Port of "Thin Client" (Running Win Pro) > (Wireless) RDP to Remote Desktop Server > Eyebeam Softphone Client > VOIP Server > Caller (cell phone or another in-office extension)

During a live phone call, the incoming voice (From the caller played through the USB Headset on the remote client computer) is all broken up and barely intelligible.

The outgoing voice recorded from the remote client computer and sent to the caller is flawless.

Any other audio playback is flawless as well. For example, the caller can call and leave a voicemail on the VOIP server and then the user can play the voicemail back through the headset on the remote client and it's clear as day.

Is there anything I can do to improve the audio playback sound quality during a live call?

Note: I am currently using "Play on this computer" versus "Play on remote computer" as the server does not have a sound card installed.


Your setup is suboptimal -- I'd even go so far as to say that the setup you described is actively hostile to VoIP communications.

A few key items: 1. You're sending video and audio both ways over the RDP session. 2. You're going over a wireless network.
While this often works fine it's generally not a great idea, especially on common WiFi (not dedicated to VoIP) - lots of traffic/noise can delay or lose voice packets. 3. If you're not the only person on the RDP server the shared workload can really mess you up.
VoIP generally doesn't play well with virtualization... 4. SIP is UDP - Packets that arrive out of order get dropped.
All the stuff above can lead to dropped/out-of-order packets.

Things to consider:

  • You can troubleshoot your network (try a WiFi VoIP client, or a plug-in phone),
  • You can try troubleshooting the VoIP-over-RDP thing (connect the thin client to a dedicated machine and see how things work ; try a softphone that's not going through RDP)
  • If you haven't already you can set up QoS to prioritize VoIP traffic (this won't help WiFi congestion or server load though).
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    +1 for "the setup you described is actively hostile to VoIP communications". A/V over RDP over WiFi to a RDP (virtual?) server running a softphone talking to a VOIP server... the only missing things are carrier pigeons. – Massimo Sep 27 '11 at 20:18
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    +1 for "the only missing things are carrier pigeons." – ErnieTheGeek Sep 27 '11 at 20:23
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    @Massimo: The latency is a bitch over avian carrier, though. Talk about a long, fat pipe. – Evan Anderson Sep 27 '11 at 22:05
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    There is no method to prioritize the USB traffic over the RDP stream. It's not VoIP traffic at that point-- it's just USB virtual channel protocol (msdn.microsoft.com/en-us/library/ff635589(v=prot.10).aspx). There's no QoS capabilities in these virtual channels. You'd have to just prioritize RDP traffic and that's not likely to buy you much. – Evan Anderson Sep 27 '11 at 22:08
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    @EvanAnderson I live in an area of high feline density. You don't want to know what the packet loss percentages are. – voretaq7 Sep 28 '11 at 4:38

The solution to this problem was to utilize USB over Ethernet software.

  • Didn't you say you're using WiFi, not Ethernet? – Chris S Jan 26 '12 at 20:56
  • Correct. Clarification: "USB over IP Software" – Earls Feb 1 '12 at 5:23

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