<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><base target="_blank"><style><!--@import url("file:///E:LMQLightingMail/datascrollbar.css");
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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple style='margin-left:9.0pt;margin-top:9.0pt;margin-right:9.0pt;margin-bottom:9.0pt'><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I would imagine that it is handle through basic asynchronous sample rate conversion. There is a lot of literature out there on the different techniques to do this. A common method is sinc interpolation. This is how I have handle these types of things in the past.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Vasant Shridhar<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin:0in;margin-bottom:.0001pt'><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> speex-dev-bounces@xiph.org [mailto:speex-dev-bounces@xiph.org] <b>On Behalf Of </b>LiMaoquan2000<br><b>Sent:</b> Tuesday, April 12, 2011 12:36 AM<br><b>To:</b> speex-dev<br><b>Subject:</b> [Speex-dev] Anyone knows how microsoft AEC can deal with mismatches between clocks of capture and render streams?<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p><span style='font-size:13.5pt'>Hi all,</span><o:p></o:p></p><p><span style='font-size:13.5pt'>We all know that mismatch between clocks of ADCs of far-end voice and near-end voice is not allowed in a time-domain or frequency-domain LMS based AEC system. It means that capture and render audio streams must be synchronized to a same sample rate. However, I found that this restriction is removed in microsoft AEC from Windows XP SP1. Anyone knows how microsoft AEC do it? This technology is much helpful for us to implement AEC in common PC. We know that most low-cost soundcards have different sample rates in capturing and rendering which prevents LMS based AEC from being used in most computer.</span><o:p></o:p></p><p><a href="http://msdn.microsoft.com/en-us/library/ff536174(VS.85).aspx"><span style='font-size:13.5pt'>http://msdn.microsoft.com/en-us/library/ff536174(VS.85).aspx</span></a><br><em><span style='font-size:13.5pt'>In Windows XP, the clock rate must be matched between the capture and render streams. The AEC system filter implements no mechanism for matching sample rates across devices. ............. In Windows XP SP1, Windows Server 2003, and later, this limitation does not exist. The AEC system filter correctly handles mismatches between the clocks for the capture and render streams, and separate devices can be used for capture and rendering.</span></em><o:p></o:p></p><p><span style='font-size:13.5pt'>Maoquan</span><o:p></o:p></p></div></body></html>