Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 7 Jan 2003 13:59:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 7 Jan 2003 13:59:48 -0500 Received: from amsfep13-int.chello.nl ([213.46.243.24]:57439 "EHLO amsfep13-int.chello.nl") by vger.kernel.org with ESMTP id ; Tue, 7 Jan 2003 13:59:47 -0500 Message-ID: <3E1B25A2.7020508@users.sf.net> Date: Tue, 07 Jan 2003 20:08:18 +0100 From: Thomas Tonino User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3a) Gecko/20021212 X-Accept-Language: en-us, en MIME-Version: 1.0 To: linux-kernel Subject: Re: [Asterisk] DTMF noise References: <20030107140012$1b66@gated-at.bofh.it> <20030107150006$4896@gated-at.bofh.it> In-Reply-To: <20030107150006$4896@gated-at.bofh.it> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 981 Lines: 29 Mark Spencer wrote: > The DTMF detector in the linux kernel is fairly simplistic and doesn't do > many relative energy tests. The Zapata library has a much better tone > detector, but it is FP, and so would have to be made fixed point. If > nothing else, it may provide some lessons for the ISDN folks. I remember that a good DTMF decoder can be very simplistic: DTMF was designed for that. The idea is: - separate the high tones from the low tones. - amplify clip the high band and the low band separately - run the tone decoders on the clipped signals The clipping stage would make sure that only relatively pure tones will trigger the detector. See also http://groups.google.com/groups?selm=7462%40accuvax.nwu.edu Thomas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/