From owner-freebsd-multimedia Mon Dec 22 21:50:38 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id VAA05391 for multimedia-outgoing; Mon, 22 Dec 1997 21:50:38 -0800 (PST) (envelope-from owner-freebsd-multimedia) Received: from labinfo.iet.unipi.it (labinfo.iet.unipi.it [131.114.9.5]) by hub.freebsd.org (8.8.7/8.8.7) with SMTP id VAA05371 for ; Mon, 22 Dec 1997 21:50:32 -0800 (PST) (envelope-from luigi@labinfo.iet.unipi.it) Received: from localhost (luigi@localhost) by labinfo.iet.unipi.it (8.6.5/8.6.5) id FAA03728; Tue, 23 Dec 1997 05:23:36 +0100 From: Luigi Rizzo Message-Id: <199712230423.FAA03728@labinfo.iet.unipi.it> Subject: Re: precise soundcard tuning ? To: hasty@rah.star-gate.com (Amancio Hasty) Date: Tue, 23 Dec 1997 05:23:35 +0100 (MET) Cc: hasty@rah.star-gate.com, steve@visint.co.uk, multimedia@freebsd.org In-Reply-To: <199712222115.NAA02470@rah.star-gate.com> from "Amancio Hasty" at Dec 22, 97 01:15:21 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Sender: owner-freebsd-multimedia@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > Strange, according to Jim's test program my guspnp is about > .002 accurate. > 520000 64.9858 8001.75 > 528000 65.9856 8001.75 > 536000 66.9854 8001.74 quite reasonable result (I assume that you have run the test for a much longer time, or the 200us differences that you see are not that significant). But the problem is that some sampling rates might not be so precise (due to the sample rate not being an exact divisor of the XTAL frequency) and these differences accumulate over time. The problem is often worse at high sampling rates (where you need a smaller divisor). Even in your case, you have a drift of roughly 1 second/hour. Cheers Luigi