<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<STYLE type=text/css> <!--@import url(E:\LMQ\LightingMail\\data\scrollbar.css); -->p{margin:0px;padding:0px;}; </STYLE>
<META content="text/html; charset=utf-8" http-equiv=Content-Type>
<STYLE>BLOCKQUOTE{margin-Top: 0px; margin-Bottom: 0px; margin-Left: 2em}; </STYLE>
<META name=GENERATOR content="MSHTML 9.00.8112.16421"><BASE target=_blank><BASE
target=_blank></HEAD>
<BODY
style="BORDER-RIGHT-WIDTH: 0px; MARGIN: 12px; BORDER-TOP-WIDTH: 0px; BORDER-BOTTOM-WIDTH: 0px; BORDER-LEFT-WIDTH: 0px"
topMargin=10 marginwidth="0" marginheight="0">
<P><FONT size=4>Hi all,</FONT></P>
<P><FONT size=4></FONT> </P>
<P><FONT size=4>I remember someone (sorry I forgot his name) told me that AC97
capturing codec has its own PLL clock generator to fit for S/PDIF input which
has its own clock. So the mismatch between clocks of capturing and rendering is
unavoidable.</FONT></P>
<P><FONT size=4></FONT> </P>
<P><FONT size=4>But after reading the Audio Codec 97 Revision 2.3 Revision 1.0
document carefully, I can only find proofs that the mismatch should not
exist.</FONT></P>
<P><FONT size=4></FONT> </P>
<P><FONT size=4>In chapter 3.4, page 23, <EM>clocking for Multiple Codec
Implementations</EM>, it is said that "<EM>To keep the system synchronous, all
Primary and Secondary Codec clocking must be derived from the same clock source,
so they are operating on the same time base. In addition, all AC-link protocol
timing must be based on the BIT_CLK signal, to ensure that everything on the
AC-link will be synchronous.</EM>".</FONT></P>
<P><FONT size=4></FONT> </P>
<P><FONT size=4>In Figure 8. <EM>Controller to Multiple Codec connections at
page 21</EM>, you can also find that AC97 controller and all Codecs share the
same SYNC and BIT_CLK signal.</FONT></P>
<P><FONT size=4></FONT> </P>
<P><FONT size=4>So anyone could give me more details for the reason of mismatch
between sample rates of of capturing and rendering? Which is a HUGE OBSTACLE for
all LMS based acoustic echo cancellers, such as speex AEC.</FONT></P>
<P><A href="http://msdn.microsoft.com/en-us/library/ff536174(VS.85).aspx"><FONT
size=4></FONT></A> </P>
<P><FONT size=4>Maoquan</FONT></P></BODY></HTML>