Hello,

On 7/3/07, Neil Carrott <[EMAIL PROTECTED]> wrote:
> We have a SIP phone developed using sipXtapi that works fine on other
> versions of Windows, but in Windows Vista the voice quality is so poor that
> nothing can be made out. From what we can tell the RTP looks like it is
> coming through to the PC correctly and it can be played back in other
> applications and sounds good.
>
> Does anyone have any ideas on why the voice quality is so poor in the SIP
> phone and whether there are any solutions available?

Basic idea is that we had no chance to work on audio quality under
Windows Vista. Core developers still use Windows XP (and Linux)
to test with. Though, patches, improving audio quality are always
welcome, we're interested in good audio quality.

First thing I could recommend you is to test audio quality with new
audio input/output system, we're developping now. it *may* have
better quality in your case (under WinXP it do have better quality).
Simplest way to test it - remove x's before these preprocessor
definitions in sipXmediaAdapterLib:
DISABLE_DEFAULT_PHONE_MEDIA_INTERFACE_FACTORY
ENABLE_TOPOLOGY_FLOWGRAPH_INTERFACE_FACTORY
This will switch from old-style CpPhoneMediaInterface and new-style
CpTopologyGraphInterface. Later still do not have all features of
first one, but use new input/output system, so you'll be able to
test it. Then you could use sipXmediaAdapterLibTest or just
use your sipphone to test audio quality.

If you want to work on audio quality, I recommend you to work
with new input/output system, as old system will be undermaintained
and removed in foreseeable future. And it is simply worse then new
one. Starting point for you could be MpodWinMM.cpp and MpidWinMM.cpp
in sipXmediaLib project.

Anyway, good luck to you! And do not forget to report your testing results.

-- 
Regards,
Alexander Chemeris.

SIPez LLC.
SIP VoIP, IM and Presence Consulting
http://www.SIPez.com
tel: +1 (617) 273-4000
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