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From: Hans Petter Selasky <hselasky@c2i.net>
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Date: Mon, 9 Jul 2007 21:39:10 +0200
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Cc: Christopher Davis <loafier@freebsd.org>, multimedia@freebsd.org
Subject: Re: Audio driver template
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On Monday 09 July 2007 20:47, Christopher Davis wrote:
> http://people.freebsd.org/~cg/template.c
>
> Thought I would take a look at the audio driver template as
> part of my task to modernize drivers, soc2007. I would simplify
> the read and write functions to avoid using the bus tag and
> handle, but I'm not sure what else to do to bring it up to date.
>
> How else can it be improved?

Regarding echo cancelling, you should add some code that time-stamps the audio 
data, and computes the current number of bytes in the RX/TX FIFOs!

Look at the exported functions in the Echo Canceller for I4B:

http://www.turbocat.net/~hselasky/isdn4bsd/sources/src/sys/i4b/layer1/i4b_echo_cancel.c

The echo canceller above is a work in progress.

--HPS