[Speex-dev] Anyone knows how microsoft AEC can deal with mismatches between clocks of capture and render streams?

[Shridhar, Vasant]

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.

Vasant Shridhar

From: speex-dev-bounces at xiph.org [mailto:speex-dev-bounces at xiph.org] On Behalf Of LiMaoquan2000
Sent: Tuesday, April 12, 2011 12:36 AM
To: speex-dev
Subject: [Speex-dev] Anyone knows how microsoft AEC can deal with mismatches between clocks of capture and render streams?


Hi all,

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.

http://msdn.microsoft.com/en-us/library/ff536174(VS.85).aspx
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.

Maoquan
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